A pattern language

The slab is the easiest, cheapest, and most natural way to lay a ground floor.

1009

CONSTRUCTION

When the ground is relatively level, a concrete slab which sits directly on the ground is the most natural and cheapest way of building a ground floor. Wood floors are expensive, need air space underneath them, and need to be built up on continuous foundation walls or beams. Prefabricated floor panels also need a structure of some sort to support them. A slab floor, on the other hand, uses the earth for support, and can supply the foundations which are needed to support walls, by simple thickening.

The one trouble with slabs is that they can easily feel cold and damp. We believe that this feeling is at least as much a psychological one as a physical one (given a well-made and insulated slab), and that the feeling is most pronounced with slabs that are on grade. We therefore propose that the slab be raised from the ground. This can be done by not excavating the ground at all, instead only leveling it, and placing the usual bed of rubble and gravel on top of the ground. (In normal practice, the ground is excavated so that the top of the rubble is slightly below grade, and the top of the slab only just above the ground.)

Therefore:

Build a ground floor slab, raised slightly—six or nine inches above the ground—by first building a low perimeter wall around the building, tied into the column foundations, and then filling it with rubble, gravel, and concrete.

fill

concrete

sand

nibble

TTTTE7

brick edge

brick

raised

♦J*

Finish the public areas of the floor in brick, or tile, or waxed and polished lightweight concrete, or even beaten earth; as for those areas which will be more private, build them one

IOIO

step up or one step down, with a lightweight concrete finish that can be felted and carpeted—floor surface (233).

Build the low wall which forms the edge of the ground floor slab out of brick, and tie it directly into all the terraces and paths around the building—connection to the earth (168), soft tile and brick (248). If you are building on a steep sloped site, build part of the ground floor as a vaulted floor instead of excavating to form a slab—floor-ceiling vaults (219). . . .

ion

1012

. . . if you use root foundations (214), the columns must be made at the same time as the foundations, since the foundation and the column are integral. The height, spacing, and thickness of the various columns in the building are given by final column distribution (213). This pattern describes the details of construction for the individual columns.

In all the world’s traditional and historic buildings, the columns are expressive, beautiful, and treasured elements. Only in modern buildings have they become ugly and meaningless.

The fact is that no one any longer knows how to make a column which is at the same time beautiful and structurally efficient. We discuss the problem under seven separate headings:

1. Columns feel uncomfortable unless they are reasonably thick and solid. This feeling is rooted in structural reality. A long thin column, carrying a heavy load, is likely to fail by buckling: and our feelings, apparently, are particularly tuned in to this possibility.

We do not wish to exaggerate the need for thickness. Taken too far, it could easily become a mannerism of a rather ridiculous sort. But columns do need to be comfortable and solid, and only thin when they are short enough to be in no danger of buckling. When the column is a free-standing one, then the need for thickness becomes essential. This is fully discussed under column place (226).

2. Structural arguments lead to exactly the same conclusion. Thin, high strength materials, like steel tubes and prestressed concrete, arc ruled out by good materials (207). Lower strength materials which are ecologically sound have to be relatively fat to cope with the loads.

3. The column must be cheap. An 8 by 8 solid wood column is too expensive; thick brick or stone columns are almost out of the question in today’s market.

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CONSTRUCTION

4. It must be warm to the touch. Concrete columns and painted steel columns have an unpleasant surface and are not very easy to face.

5. If the column takes bending, the highest strength materials should be concentrated toward the outside. Buckling and bending strength both depend on the moment of inertia, which is highest when the material is as far as possible from tire neutral axis. A stalk of grass is the archetypal example.

IOI4

21 6 BOX COLUMNS

6. The column must be easy to connect to foundations, beams, and walls. Precast concrete columns are very hard to connect. So are metal columns. Brick columns are easy to connect to brick walls—not to the lighter weight skin structures required by wall

MEMBRANE (2 I 8) .

7. The column must be hand nailable, and hand cuttable to make on-site modification and later repair as easy as possible. Again, current materials do not easily meet this requirement.

A column which has all these features is a box column, where the hollow tube can be made as thick as is required, and then filled with a strong compressive material. Such a column can be made cheaper than comparable wood and steel columns; the outer skin can be made with a material that is beautiful, easy to repair, and soft to the touch; the column can be stiffened for bending, either by the skin itself, or by extra reinforcing; and, for structural integrity, the fill material can be made continuous with the column’s footings and beams.

An example of a box column which we have built and tested is a wooden box column, made with I inch wooden planks and filled with lightweight concrete the same density as wood, so that it has the overall volume and mass of a heavy 8 inch solid column. The drawing opposite shows these wooden box columns being made.

Box columns can be made in many other ways. One kind is made by stacking 8 by 8 inch lightweight concrete blocks, and filling the cavity with a concrete of the same density. Some wire reinforcing inside the column is required to give the column tensile strength. A hollow brick column, filled with earth is

TOWNS

within reach of at least one downtown and also that all the downtowns are worth reaching for and really have the magic of a great metropolis.

Therefore:

Put the magic of the city within reach of everyone in a metropolitan area. Do this by means of collective regional policies which restrict the growth of downtown areas so strongly that no one downtown can grow to serve more than 300,000 people. With this population base, the downtowns will be between two and nine miles apart.

catch basins of 300,000

two to nine miles apart .

- - x :

(g) ' ^ specialties

_d f V*-

downtowns ,

*£♦

Treat each downtown as a pedestrian and local transport area— LOCAL TRANSPORT AREAS (il), PROMENADE (3 I ) , with good transit connections from the outlying areas—web of public transportation (16); encourage a rich concentration of night life within each downtown—night life (33), and set aside at least some part of it for the wildest kind of street life—carnival (58), DANCING IN THE STREET (63) . . . .

CONSTRUCTION

another possibility. Concrete, vinyl, and terracotta sewer pipe filled with lightweight concrete and reinforced with mesh; a resin-impregnated cardboard tube filled with earth; or two concentric cardboard tubes with the outer ring filled with concrete and the inner ring filled with earth; still another is made from a tube of chicken wire wesh, filled with rubble, plastered and whitewashed on the outside. And still another can be made with self-aligning hollow tiles for the skin. The tiles can be molded by hand with a hand press—in concrete or tile; the soft tile will make beautiful rose red, soft warm columns.

Therefore:

Make the columns in the form of filled hollow tubes, with a stiff tubular outer skin, and a solid core that is strong in compression. Give the skin of the column some tensile strength—preferably in the skin itself, but perhaps with reinforcing wires in the fill.

1016

As you already know, It is best to build the columns integral with root foundations (214) on the ground floor, or integral with the floor-ceiling vaults (219) on upper floors, and to fill them in one continuous pour. Once the columns are in position, put in the perimeter beams (217), and fill the beams at the same time that you fill the upper part of the column. If the column is free standing, put in column braces or column capitals—column connection (227)—to brace the connection between the two. And make the columns especially thick, or build them in pairs, where they are free-standing, so that they form a COLUMN PLACE (226). . . .

I0l8

. . . this pattern helps to complete box columns (216), by-tying the tops of the columns together once they are in position. It also helps to form the bearing surface for the edge of the floor-ceiling vaults (219). For this reason, the positions of the perimeter beams must correspond exactly to the edges of the vaults laid out in floor and ceiling layout (210).

❖ ❖ ❖

If you conceive and build a room by first placing columns at the corners, and then gradually weaving the walls and ceiling round them, the room needs a perimeter beam around its upper edge.

It is the beam, connecting the columns which creates a volume you can visualize, before it is complete; and when the columns are standing in the ground, you need the actual physical perimeter beam, to generate this volume before your eyes, to let you see the room as you are building it, and to tie the tops of the columns together, physically.

These reasons are conceptual. But of course, the conceptual simplicity and rightness of the beam around the room comes, in the end, from the more basic fact that this beam has a number of related structural functions, which make it an essential part of any room built as a natural structure. The perimeter beam has four structural functions:

1. It forms the natural thickening between the wall membrane and vault membrane, described in efficient structure (206).

2. It resists the horizontal thrust of the ceiling vault, wherever there are no outside external buttresses to do it, and no other vaults to lean against.

3. It functions as a lintel, wherever doors and windows pierce the wall membrane.

4. It transfers loads from columns in upper storys to the columns and the wall membrane below it, and spreads these loads out to distribute them evenly between the columns and the membrane.

CONSTRUCTION

These functions of the perimeter beam show that the beam must be as continuous as possible with walls and columns above, the walls and columns below, and with the floor. If we follow good materials (207), the beam must also be easy to make, and easy to cut to different lengths.

Available beams do not meet these requirements. Steel beams and precast or prestressed beams cannot easily be tied into the wall and floor to become continuous with these membranes. Far more important, they cannot easily be cut on site to conform to the exact dimensions of the different rooms which will occur in an organic plan.

1020 217 PERIMETER beams

Of course, wood beams meet both requirements: they are easy to cut and can be tied along their lengths to wall and floor membranes. However, as we have said in good materials (207), wood is unavailable in many places, and even where it is available, it is becoming scarce and terribly expensive, especially in the large sizes needed for beams.

To avoid the use of wood, we have designed a perimeter beam—shown opposite—which is consistent with our box column, and designed to be used together with it. It is a beam made by first nailing up a channel made of wooden planks to the columns, before the wall membranes are made; then putting in reinforcing, and filling up with ultra-lightweight 60 pounds per cubic foot concrete, after the walls are made and filled. This beam is excellent for continuity. The wooden channel can first be made continuous with other skin elements by nailing, and the fill can then be made continuous by filling columns and beams and walls and vault in one continuous pour—see wall membranes (218)

and FLOOR-CEILING VAULTS (2 I 9).

Of course, there are many other ways of making a perimeter beam. First of all, there are several variants of our design: the U-shaped channel can be made of fiberboard, plywood, precast lightweight concrete, and, in every case, filled with lightweight concrete. Then there are various traditional perimeter beams— the Japanese version or the early American versions come to mind. And then there are a variety of structures which are not exactly even beams—but still act to spread vertical loads and counteract horizontal thrusts. A row of brick arches might function in this way, in a far fetched case so might a tension ring of jungle creeper.

Therefore:

Build a continuous perimeter beam around the room, strong enough to resist the horizontal thrust of the vault above, to spread the loads from upper stories onto columns, to tie the columns together, and to function as a lintel over openings in the wall. Make this beam continuous with columns, walls and floor above, and columns and walls below.

CONSTRUCTION

Remember to place reinforcing in such a way that the perimeter beam acts in a horizo?ital direction as well as vertical. When it forms the base for a floor-ceiling vault (219) it must be able to act as a ring beam to resist all those residual horizontal outward thrusts not contained by the vault. Strengthen the connection between the columns and the perimeter beam with diagonal braces where the columns are free standing—

COLUMN CONNECTION (227). . . .

1022 218 wall membrane*

. . . according to efficient structure (206) and final column distribution (213), the wall is a compressive load-bearing membrane, “stretched” between adjacent columns and continuous with them, the columns themselves placed at frequent intervals to act as stiffeners. The intervals vary from floor to floor, according to column height; and the wall thickness (membrane thickness) varies in a similar fashion. If the column stiffeners arc already in place according to box column (216), this pattern describes the way to stretch the membrane from column to column to form the walls.

* * *

In organic construction the walls must take their share of the loads. They must work continuously with the structure on all four of their sides; and act to resist shear and bending, and take loads in compression.

When walls are working like this, they arc essentially structural membranes: they are continuous in two dimensions; together with stiffeners and columns they resist loads in compression; and they create a continuous rigid connection between columns, beams, and floors, both above and below, to help resist shear and bending.

By contrast, curtain walls and walls which are essentially “infill,” do not act as membranes. They may function as walls in other respects—-they insulate, enclose, they define space—but they do not contribute to the overall structural solidity of the building. They let the frame do all the work; structurally they are wasted. | For the details of the argument that every part of the structure must cooperate to take loads, see efficient structure (206).]

A membrane, on the other hand, makes the wall an integral thing, working with the structure around it. How should we build such a wall membrane?

good materials (207) tells us that we should use hand cuttable, nailable, ecologically sound materials, which one can work with home tools, with the emphasis on earthen fill materials and sheet materials.

gradual stiffening (208) tells us that the process of building should be such that one can start with a flimsy structure and stiffen it during the course of construction, as materials are put in place, so that the process can be smooth and continuous.

218 wat.l membrane

An example of such a wall that we have built and tested uses gypboard for the inner skin, ship-lapped wooden boards for the outer skin and ultra-lightweight concrete for the fill. The wall is built by fixing nailing blocks to the sides of columns. We nail the skin to the nailing blocks, put chickenwire into the cavity to reinforce the concrete against shrinkage, and then pour the lightweight concrete into the cavity. The wall needs to be braced during pouring, and you can’t pour more than two or three feet at a time: the pressure gets too great. The last pour fills the perimeter beam and the top of the wall, and so makes them integral. The drawing opposite shows one way that we have made this particular kind of wall membrane.

This wall is solid (about the density of wood), has good acoustic and thermal properties, can easily be built to conform to free and irregular plans, and can be nailed into. And because of its stiffeners, the wall is very strong for its thickness.

Other versions of this pattern: (i) The skin can be formed from hollow structural tiles or concrete blocks, with a concrete or earthen fill. (2) The exterior skin might be brick, the interior skin plywood or gypboard. In either case the columns would have to be hollow tile, or concrete pipe, or other masonry box columns. (3) The skin might be formed with wire mesh, gradually filled with concrete and rubble, and stuccoed on the outside, with plaster on the inside. The columns in this case can be built in the same way—out of a wire mesh tube filled with rubble and concrete. (4) It may also be possible to use gypboard for both skins, inside and out. The gypboard on the outer side could then be covered with building paper, lath, and stucco.

Therefore:

Build the wall as a membrane which connects the columns and door frames and windows frames and is, at least in part, continuous with them. To build the wall, first put up an inner and an outer membrane, which can function as a finished surface; then pour the fill into the wall.

CONSTRUCTION

inner and outer membrane

Remember that in a stiffened wall, the membranes can be much thinner than you might expect, because the stiffeners prevent buckling. In some cases they can be as thin as two inches in a one story building, three inches at the bottom of a two-story building and so on—see final column distribution (213).

Membranes can be made from hollow tile, lightweight concrete block, plywood, gypboard, wood planks, or any other sheet type material which would make a nice surface, which is easy to nail into, comfortable to touch, and so on. If the inner sheet is gypsum board, it can be finished with a skim coat of plaster—soft inside walls (235). The outer sheet can be made of 1 inch boards, tongue and grooved; or exterior grade plywood; or exterior board hung with tile, shingles, or plastered—lapped outside walls (234). It is also possible to build the outer skin of brick or tile: in this case, columns must be of the same material—soft tile and brick (248). . . .

1026

219 FLOOR-CEILING VAULTS**

I O27

. . . we have already discussed the fact that ordinary joist floors and slab floors are inefficient and wasteful because the tension materials they use to resist bending are less common than pure compression materials—efficient structure (206), good materials (207), and that it is therefore desirable to use vaults wherever possible. This pattern gives the shape and construction of the vaults. The vaults will help to complete floor and ceiling layout (210), and perimeter beams (217); and, most important of all, they will help to create the ceiling height variety (190) in different rooms.

We seek a ceiling vault shape which will support a live load on the floor above, form the ceiling of the room below, and generate as little bending and tension as possible so that compressive materials can be relied on.

The vault shape is governed by two constraints: the ceiling cannot be lower than about 6 feet at the edge of the room, except in occasional attic rooms; and the ceiling in the middle of the room should vary with the room size (8 to 12 feet for large rooms, 7 to 9 feet for middle sized rooms, and 6 to 7 feet for the very smallest alcoves and corners—see ceiling height variety (190)).

We know, from structural considerations, that a circular shell dome will generate virtually no bending moments when its rise is at least 13 to 20 per cent of its diameter. (This is established in studies and tests of shell structures, and is corroborated by our own computer studies.) For a room 8 feet across, this requires a rise of about 18 inches, making a total height of 7 to 8 feet in the middle; for a room 15 feet across, it requires a rise of 2-3 feet, making a height of 8 to 10 feet in the middle.

Luckily, these vault heights are just congruent with the needed ceiling heights. We may say, therefore, that the ideal vault for an inhabited space is one which springs from 6 to 7 feet at the edge, and rises 13 to 20 per cent of the smaller diameter.

There are various possible ways of making a circular or elliptical vault spring from a square or rectangular room.

I. One type of vault is made by arching diagonal ribs from corner to corner; and then spacing straight line elements across the ribs.

2. Another type is a pure dome supported on squinches.

3. Another is based on a rectangular grid of arched ribs. The edge ribs are entirely flat, and the center ribs have the greatest curvature. In the end, each part of the vault is curved in three dimensions, and the corners are slightly flattened.

Each of these three vaults makes sense in slightly different circumstances. The first is the easiest to conceive, but it has a slight structural disadvantage: its surface panels are curved in one direction only—because they are made of straight line elements —and cannot therefore achieve the strength of a doubly curved vault. The second is the hardest to conceive; however, it comes naturally from the intersection of a spherical shape and a rectangular one. If one were to make a vault by using a balloon as a form, pushed up within the perimeter beams, the second type would be the easiest to use. In the particular building technique we have been using, the third type is easiest to use, because it is particularly

CONSTRUCTION

simple to lay out the arched ribs which provide the formwork. It flattens out at the coiners, which could create bending moments and require tension materials. However, in lightweight concrete we have found that it docs not require any more than the shrinkage reinforcement, which is needed anyway.

Wc shall now describe a very simple way of making a vault. Bear in mind that wc considered it essential that the vault be built up gradually, and that it could be fitted to any room shape, without difficulty. This technique is not only cheap and simple. It is also one of the only ways wc have found of fitting a vault to an arbitrary room shape. It works for rectangular rooms, rooms that are just oft-rectangles, and odd-shaped rooms. It can be applied to rooms of any size. The height of the vault can be varied according to its position in the overall array of ceiling heights and floors—ceiling height variety (190), structure

FOLLOWS SOCIAL SPACES (2O5), FLOOR AND CEILING LAYOUT (210).

First, place lattice strips at one foot centers, spanning in one direction, from one perimeter beam to the opposite perimeter beam, bending each strip to make a sensible vault shape. Now-weave strips in the other direction, also at almost one foot centers, to form a basket. The strips can be nailed onto the form of the perimeter beam around the room. You will find that the basket is immensely strong and stable.

Now stretch burlap over the lattice strips, tacking it on the strips so it fits tightly. Paint the burlap with a heavy coat of polyester resin to stiffen it.

^I03°

The burlap-resin skin is strong enough to support I to 2 inches of lightweight concrete. In preparation for this, put a layer of chickenwire, as shrinkage reinforcement, over the stiffened burlap. Then trowel on a 1- to 2-inch layer of lightweight concrete. Once again, use the ultra-lightweight 40-60 pound concrete described in GOOD MATERIALS (2O7).

The shell which forms is strong enough to support the rest of the vault, and the floor above.

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CONSTRUCTION

The rest of the vault should not be poured until all edges are in, columns for the next floor are in position, and ducts are in— see box columns (216), duct space (229). In order to keep the weight of the vault down, it is important that even the ultralightweight concrete be further lightened, by mixing it with 50 per cent voids and ducts. Any kind of voids can be used—empty

219 FLOOR-CEILING VAULTS

beer cans, wine jugs, sono tubes, ducts, chunks of polyurethane. Or voids can be made very much like the vaults themselves by making arches with latticing between columns and then stretching burlap from these arches to the dome. The drawing opposite shows the sequence of construction.

A 16 by 20 foot vault similar to the one shown in our photographs has been analyzed by a computerized finite element analysis. The concrete was assumed to be 40 pounds perlite, with a

CONSTRUCTION

test compressive strength of 600 psi. Tensile strength is taken as 34 psi, and bending as 25.5 inch pounds per inch. These figures are based on the assumption that the concrete is unreinforced. Dead loads were figured at 60 pounds per square foot assuming 50 per cent voids in the spandrels of the vault. Live loads were taken to be 30 pounds per square foot.

According to the analysis, under such loading the largest compressive stress in this dome occurs near the base at mid points of all four sides and is 120 psi. Outward thrust is the greatest at quarter points along all four walls, and is 1769 pounds. The maximum tension of 32 psi occurs at the corners. Maximum bending is 10 inch pounds per inch. All of these are well within the capacity of the vault, and besides, shrinkage reinforcement in the vault will make it even stronger.

The analysis show's, then, that even though the vault is an impure form (it contains square panels which are actually sagging within the overall configuration of the vault shape), its structural behavior is still close enough to that of a pure vault to work essentially as a compression structure. There are small amounts of local bending; and the corner positions of the dome suffer small amounts of tension, but the chickenwire needed for shrinkage will take care of both these stresses.

Here are some other possible ways of building such a vault:

To begin with, instead of W'ood for the lattice work, many other materials can be used: plastic strips, thin metal tubes, bamboos. Other resins besides polyester resins can be used to stiffen the burlap. If resins are unavailable, then the form for the vault can be made by placing lattice strips as described, and then stretching chickenwire over it, then burlap soaked in mortar which is allowed to harden before concrete is placed. It might also be possible to use matting stiffened with glue, perhaps even papier mache.

It is possible that similar vaults could be formed by altogether different means: perhaps with pneumatic membranes or balloons. And it is of course possible to form vaults by using very traditional methods: bricks or stones, on centering, like the beautiful vaults used in renaissance churches, gothic cathedrals, and so on.

219 FLOOR-CEILING VAULTS

Therefore:

Build floors and ceilings in the form of elliptical vaults which rise between 13 and 20 per cent of the shorter span. Use a type of construction which makes it possible to fit the vault to any shaped room after the walls and columns are in position: on no account use a prefabricated vault.

When the main vault is finished, mark the positions of all those columns which will be placed on the floor above it—final column distribution (213). Whenever there are columns which are more than 2 feet away from the perimeter beam, strengthen the vault with ribs and extra reinforcing to withstand the vertical forces.

Put all the upper columns in position before you pour the floor of the vault, so that when you pour it, the concrete will pour around the column feet, and anchor them firmly in the same way that they are anchored in the foundations—root foundations (214).

To finish the under surface of the vault paint it or plaster it— soft inside walls (235). As for the floor surface above, either wax it and polish it or cover it with soft materials—floor surface (233). . . .

1035

. . . superimposed over the mosaic of subcultures (8), there is a need for a still larger cellular structure: the local transport areas. These areas, 1—2 miles across, not only help to form subcultures, by creating natural boundaries in the city, but they can also help to generate the individual city fingers in the city country fingers (3), and they can help to circumscribe each downtown area too, as a special self-contained area of local transportation-MAGIC OF THE CITY (lO).

*

Cars give people wonderful freedom and increase their opportunities. But they also destroy the environment, to an extent so drastic that they kill all social life.

The value and power of the car have proved so great that it seems impossible to imagine a future without some form of private, high-speed vehicle. Who will willingly give up the degree of freedom provided by cars? At the same time, it is undeniably true that cars turn towns to mincemeat. Somehow local areas must be saved from the pressure of cars or their future equivalents.

It is possible to solve the problem as soon as we make a distinction between short trips and long trips. Cars are not very good for short trips inside a town, and it is on these trips that they do their greatest damage. But they are good for fairly long trips, where they cause less damage. The problem will be solved if towns are divided up into areas about one mile across, with the idea that cars may be used for trips which leave these areas, but that other, slower forms of transportation will be used for all trips inside these areas—foot, bike, horse, taxi. All it needs, physically, is a street pattern that discourages people from using private cars for trips within these areas, and encourages the use of walking, bikes, horses, and taxis instead—but allows the use of cars for trips which leave the area.

Let us start with a list of the obvious social problems created by the car:

Air pollution

IO36

. . . if the roof is a flat roof garden (118), it can be built just like any floor-ceiling vault (219). But when it is a sloping roof, according to the character of sheltering roof (1 17), it needs a new construction, specifically adapted to the shape which can enclose a volume.

•5* *5* *5*

What is the best shape for a roof?

1037

For some reason, this is the most loaded, the most emotional question, that can be asked about building construction. In all our investigations of patterns, we have not found any other pattern which generates so much discussion, so much disagreement, and so much emotion. Early childhood images play a vital role; so does cultural prejudice. It is hard to imagine an Arab building with a pitched roof; hard to imagine a New England farmhouse with a Russian onion roof over a tower; hard to imagine a person who has grown up among pitched steep wooden roofs, happy under the stone cones of the trulli.

CONSTRUCTION

For this reason, in this pattern we make our discussion as fundamental as we can. We shall do everything we can to obtain the necessary features which we can treat as invariant for all roofs, regardless of people or culture—yet deep enough to allow a rich assortment of cultural variations.

We approach the problem with the assumption that there are no constraints created by techniques or availability of materials. We are merely concerned with the optimum shape and distribution of materials. Given a roughly rectangular plan, or plan composed of rectangular pieces connected, what is the best shape for the shell of the roof which covers them?

The requirements influencing the shape are these:

1. The feeling of shelter—sheltering roof (117). This requires that the roof cover a w'hole wing (that is, not merely room by room). It requires that some of the roof be highly visible— hence, that it have a fairly steep slope—and that some of the roof be flat and usable for gardens or terraces.

2. The roof must definitely contain lived-in space—that is, not just sit on top of the rooms which are all below—see sheltering roof (117). This means it needs rather a steep slope at the edge—because otherwise there is no headroom. This requires an elliptical section dome, or a barrel vault (which starts going up vertically at the edge), or a very steep slope.

3. In plan, each individual roof is a very rough rectangle, with occasional variations. This follows from the way the roofs of a building must, together, follow the social layout of the plan—

ROOF LAYOUT (2O9).

4. The roof shape must be relaxed—that is, it can be used in any plan layout—and can be generated very simply from a few generating lines which follow automatically from the plan—that is, it must not be a tricky or contrived shape which needs a lot of fiddling around to define it—structure follows social SPACES (205).

5. Structural considerations require a curved shell, dome or vault to eliminate as much bending as possible—see efficient structure (206) and good materials (207). Of course, to the extent that wood or steel or other tension materials are available, this requirement can be relaxed.

6. The roof is steep enough to shed rain and snow in climates

where they occur. Obviously, this aspect of the roof will vary from climate to climate.

These requirements eliminate the following kinds of roofs:

1. Flat roofs. Flat roofs, except roof gardens ( i i 8), are already eliminated by the psychological arguments of sheltering roofs ( i i 7) and, of course, by structural considerations. A flat roof is necessary where people are going to walk on it; but it is a very inefficient structural shape since it creates bending.

2. Pitched Roofs. Pitched roofs still require materials that can withstand bending moment. The most common material for pitched roofs—wood—is becoming scarce and expensive. As we have said in good materials (207), we believe it is most sensible to keep wood for surfaces and not to use it as a structural material, except in wood rich areas. Pitched roofs also need to be very steep, indeed, to enclose habitable space as required by sheltering roof (11 7)—and hence rather inefficient.

3. Dutch barn and mansard roofs. These roofs enclose habitable space more efficiently than pitched roofs; but they have the same structural drawbacks.

4. Geodesic domes. These domes cover essentially circular areas, and are not therefore useful in their ordinary form— cascade of roofs (116), structure follows social spaces (205). In the modified form, which comes when you stretch

CONSTRUCTION

the base into a rough rectangle, they become more or less congruent with the class of vaults defined by this pattern.

5. Cable nets and tents. These roofs use tensile materials instead of compressive ones—they do not conform to the requirements of good materials (207). They are also very inefficient when it comes to enclosing habitable space—and thus fail to meet the requirements of structure follows social spaces (205).

The roofs which satisfy the requirements are all types of rectangular barrel vaults or shells, with or without a peak, gabled or hipped, and with a variety of possible cross sections. Almost any one of these shells will be further strengthened by additional undulations in the direction of the vault. Examples of possible cross sections are given below. (Remember that this does not include those flat roof gardens (118) built over floor-ceiling vaults

(219)0

Possible roof vaults.

We have developed a range of roof vaults which are rather similar to a pitched roof—but with a convex curve great enough to eliminate bending, in some cases actually approaching barrel vaults. One is shown in the drawing opposite3 another is shown below.

Wc build the roof vault very much like the floor vaults:

1. First span the wing to be roofed with pairs of lattice strips which are securely nailed at their ends to the perimeter beam, and weighted at their apex so that the two pieces become slightly curved.

2. Make the frame for the ceiling under the roof frame at the same time according to floor-ceiling vaults (219).

3. Repeat this frame every 18 inches, until the entire wing 3s

IO41

framed. The outer one will be the same, while the inner frame for the ceiling may change according to the rooms under it.

4. Now lay burlap over the ceiling frame, then resin, then 1J/2 inches of ultra-lightweight concrete—as for floor-ceiling vaults (219).

5. Now lay burlap over the roof frame, tacking it onto the lattice strips so that there is a 3-inch scallop in between the ribs— to form structural undulations in the skin. Again, paint the burlap with resin; lay chickenwire and put a layer of lightweight concrete over the entire roof.

We have analyzed a 48-foot roof of this type by means of a computerized finite element analysis similar to the one described for floor-ceiling vaults (219). The analysis shows that the maximum membrane compressive stress in the roof is 39.6 psi; the maximum membrane tensile stress is 2.5 psi, and the maximum diagonal membrane stress which develops from the maximum shear of 41.7 psi is 1 5.2 psi. These stresses are within the capacity of the material (See allowable stresses given in floor-ceiling vault (219)). The maximum membrane bending moment is 46 inch pounds per inch which is higher than the capacity of the unreinforced section, but extrapolations from our data show that this will be comfortably taken care of by the reinforcing which is needed anyway for shrinkage. Roofs with smaller spans, for a typical wing of light (106), will be even stronger.

Of course there are dozens of other ways to make a roof vault. Other versions include ordinary barrel vaults, lamella structures in the form of barrel vaults, elongated geodesic domes (built up from struts), vaults built up from plastic sheets, or fiberglass, or corrugated metal.

But, in one way or another, build your roofs according to the invariant defined below, remembering that it lies somewhere in between the Crystal Palace, the stone vaults of Alberobello, mud huts of the Congo, grass structures of the South Pacific, and the corrugated iron huts of our own time. This shape is required whenever you are working with materials which are in pure compression.

Obviously, if you have access to wood or steel and want to use it, you can modify this shape by adding tension members. However, we believe that these tension materials will become more

Build the roof vault either as a cylindrical barrel vault, or like a pitched roof with a slight convex curve in each of the two sloping sides. Put in undulations along the vault, to make the shell more effective. The curvature of the main shell, and of the undulations, can vary with the span; the bigger the span, the deeper the curvature and undulations need to be.

Leave space for dormers at intervals along the vault—dormer windows (231), and build them integral with it. Finish the roof with roof caps (232). And once the vault is complete, it needs a waterproof paint or skin applied to its outer surface—lapped outside walls (234). It can be painted white to protect it against the sun; the undulations will carry the rainwater. . . .

within the main frame of the building_y fix the exact 'positions for openings—the doors and the windows —and frame these openings.

221. NATURAL DOORS AND WINDOWS

222. LOW SILL

223. DEEP REVEALS 2 24. LOW DOORWAY

225. FRAMES AS THICKENED EDGES

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II LOCAL TRANSPORT AREAS

Noise

Danger

111 health

Congestion

Parking problem

Eyesore

The first two are very serious, but are not inherent in the car; they could both be solved, for instance, by an electric car. They are, in that sense, temporary problems. Danger will be a persistent feature of the car so long as we go on using high-speed vehicles for local trips. The widespread lack of exercise and consequent ill health created by the use of motor-driven vehicles will persist unless offset by an amount of daily exercise at least equal to a 20 minute walk per day. And finally, the problems of congestion and loss of speed, difficulty and cost of parking, and eyesore are all direct results of the fact that the car is a very large vehicle which consumes a great deal of space.

The fact that cars are. large is, in the end, the most serious aspect of a transportation system based on the use. of cars, since it is inherent in the very nature of cars. Let us state this problem in its most pungent form. A man occupies about 5 square feet of space when he is standing still, and perhaps 10 square feet when he is walking. A car occupies about 350 square feet when it is landing still (if we include access), and at 30 miles an hour, when cars arc 3 car lengths apart, it occupies about IOOO square feet. As we know, most of the time cars have a single occupant. This means that when people use cars, each person occupies almost 100 times as much space as he does when he is a pedestrian.

If each person driving occupies an area 100 times as large as he does when he is on his feet, this means that people are 10 times as far apart. In other words, the use of cars has the overall efect of spreading people out, and keeping them apart.

The effect of this particular feature of cars on the social fabric is clear. People are drawn away from each other; densities and corresponding frequencies of interaction decrease substantially. Contacts become fragmented and specialized, since they are localized by the nature of the interaction into well-defined indoor places—the home, the workplace, and maybe the homes of a few isolated friends.

22 1 NATURAL DOORS AND WINDOWS**

. . . imagine that you are now standing in the built-up frame of a partly constructed building, with the columns and beams in

place-BOX COLUMNS (216), PERIMETER BEAMS (2I7). You

know roughly where you want doors and windows from zen VIEW (134), STREET WINDOWS (164), WINDOW PLACE (l8o), WINDOWS OVERLOOKING LIFE (192), CORNER DOORS (196). Now you can settle on the exact positions of the frames.

Finding the right position for a window or a door is a subtle matter. But there are very few ways of building which take this into consideration.

In our current ways of building, the delicacy of placing a window or a door has nearly vanished. But it is just this refinement, down to the last foot, even to the last inch or two, which makes an immense difference. Windows and doors which are just right are always like this. Find a beautiful window. Study it. See how different it would be if its dimensions varied a few inches in either direction.

Now look at the windows and doors in most buildings made during the last 20 years. Assume that these openings are in roughly the right place, but notice how they could be improved if they were free to shift around, a few inches here and there, each one taking advantage of its own special circumstances—the space immediately inside and the view outside.

It is almost always a rigid construction system, combined with a formal aesthetic, which holds these windows in such a death grip. There is nothing else to this regularity, for it is possible to relax the regularity without losing structural integrity.

It is also important to realize that this final placing of windows and doors can only be done on site, with the rough frame of the building in position. It is impossible to do it on paper. But on the site it is quite straightforward and natural; mock up the openings with scraps of lumber or string and move them around until they feel right; pay careful attention to the organization of the view and the kind of space that is created inside.

As we shall see in a later pattern—small panes (239), it is not necessary to make the windows any special dimensions, or to try and make them multiples of any standard pane size. Whatever dimensions this pattern gives each window, it will then be possible to divide it up, to form small panes, which will be different in their exact shape and size, according to the window they are in.

However, although there is no constraint on the exact dimension of the windows, there is a general rule of thumb, which will make window sizes vary: Windows, as a rule, should become smaller as you get higher up in the building.

1. The area of windows needed for light and ventilation depends on the size of rooms, and rooms are generally smaller on upper stories of the building—the communal rooms are generally on the ground floor and more private rooms upstairs.

2. The amount of daylight coming through a window depends on the area of open sky visible through the window. The higher the window, the more open sky is visible (because nearby trees and buildings obscure less)—so less window area is needed to get sufficient daylight in.

3. To feel safe on tile upper stories of a building, one wants more enclosure, smaller windows, higher sills—and the higher off the ground one is, the more one needs these psychological protections.

Therefore:

On no account use standard doors or windows. Make each window a different size, according to its place.

Do not fix the exact position or size of the door and win-

221 NATURAL DOORS AND WINDOWS

dow frames until the rough framing of the room has actually been built, and you can really stand inside the room and judge, by eye, exactly where you want to put them, and how big you want them. When you decide, mark the openings with strings.

Make the windows smaller and smaller, as you go higher in the building.

** ,

, _ variation in window size

* a • £j.

m 5?

the position of the doors and windows “felt”

Fine tune the exact position of each edge, and mullion, and sill, according to your comfort in the room, and the view that the window looks onto—low sill (222), deep reveals (223). As a result, each window will have a different size and shape, according to its position in the building. This means that it is obviously impossible to use standard windows and even impossible to make each window a simple multiple of standard panes. But it will still be possible to glaze each window, since the procedure for building the panes makes them divisions of the whole, instead of making up the whole as a multiple of standard panes—small panes (239). . . .

1049

. . . this pattern helps to complete natural doors and windows (221), and the special love for the view, and for the earth outside, which zen view (134), window place (180) and windows overlooking life (192) all need.

One of a window’s most important functions is to put you in touch with the outdoors. If the sill is too high, it cuts you off.

The “right” height for a ground floor window sill is astonishingly low. Our experiments show that sills which are 13 or 14 inches from the floor are perfect. This is much lower than the window sills which people most often build: a standard window sill is about 24 to 36 inches from the ground. And it is higher than French doors and windows which usually have a bottom rail of 8 to 10 inches. The best height, then, happens to be a rather uncommon one.

We first give the detailed explanation for this phenomenon, and we then explain the modifications which are necessary on upper floors.

People are drawn to windows because of the light and the view outside—they are natural places to sit by when reading, talking, sewing, and so on, yet most windows have sill heights of 30 inches or so, so that when you sit down by them you cannot see the ground right near the window. This is unusually frustrating—you almost have to stand up to get a complete view.

In “The Function of Windows: A Reappraisal” (Building Science, Vol. 2, Pergamon Press, 1967, pp. 97-121), Thomas Markus shows that the primary function of windows is not to provide light but to provide a link to the outside and, furthermore, that this link is most meaningful when it contains a view of the ground and the horizon. Windows with high sills cut out the view of the ground.

On the other hand, glass all the way down to the floor is undesirable. It is disturbing because it seems contradictory and

105 1

even dangerous. It feels more like a door than a window; yon have the feeling that you ought to be able to walk through it. If the sill is 12 to 14 inches high, you can comfortably see the ground, even if you are a foot or two away from the window, and it still feels like a window rather than a door.

On upper stories the sill height needs to be slightly higher. The sill still needs to be low to see the ground, but it is unsafe if it is too low. A sill height of about 20 inches allows yon to see most of the ground, from a chair nearby, and still feel safe.

Therefore:

When determining exact location of windows also decide which windows should have low sills. On the first floor, make the sills of windows which you plan to sit by between 12 and 14 inches high. On the upper stories, make them higher, around 20 inches.

Make the sill part of the frame, and make it wide enough to put things on—waist-high shelf (201), frames as thickened edges (225), windows which open wide (236). Make the window open outward, so that you can use the sill as a shelf, and so that you can lean out and tend the flowers. If you can, put flowers right outside the window, on the ground or raised a little, too, so that you can always see the flowers from inside the room—raised flowers (245). . . .

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. . . this pattern helps to complete the work of light on two sides of every room (15 9), by going even further to reduce glare; and it helps to shape the frames as thickened edges (225).

Windows with a sharp edge where the frame meets the wall create harsh, blinding glare, and make the rooms they serve uncomfortable.

They have the same effect as the bright headlights of an oncoming car: the glare prevents you from seeing anything else on the road because your eye cannot simultaneously adapt to the bright headlights and to the darkness of the roadway. Just so, a window is always much brighter than an interior wall; and the walls tend to be darkest next to the window’s edge. The difference in brightness between the bright window and the dark wall around it also causes glare.

Glare . . . and no glare.

To solve this problem, the edge of the window must be splayed, by making a reveal between the window and the wall. The splayed reveal then creates a transition area—a zone of intermediate brightness—between the brightness of the window and the darkness of the wall. If the reveal is deep enough and the angle just right, the glare will vanish altogether.

But the reveal must be quite deep, and the angle of the splay quite marked. In empirical studies of glare, Hopkinson and

Petherbridge have found: (i) that the larger the reveal is, the less glare there is; (2) the reveal functions best, when its brightness is just halfway between the brightness of the window and the brightness of the wall. (“Discomfort Glare and the Lighting of Buildings,” Transactions of the Illuminating Engineering Society, Vol. XV, No. 2, 1950, pp. 58—59.)

Our own experiments show that this happens most nearly, when the reveal lies at between 50 and 60 degrees to the plane of the window; though, of course, the angle will vary with local conditions. And, to satisfy the need for a “large” reveal, we have found that the reveal itself must be a good 10 to 12 inches wide.

Therefore:

Make the window frame a deep, splayed edge: about a foot wide and splayed at about 50 to 60 degrees to the plane of the window, so that the gentle gradient of daylight gives a smooth transition between the light of the window and the dark of the inner wall.

*£♦

Build the depth of the frame so that it is continuous with the structure of the walls—frames as thickened edges (225) ; if the wall is thin, make up the necessary depth for the reveal on the inside face of the wall, with bookshelves, closets or other thick walls (197) ; embellish the edge of the window even further, to make light even softer, with lace work, tracery, and climbing plants—filtered light (238), half-inch trim (240) , CLIMBING PLANTS (246) . . . .

A PATTERN LANGUAGE

headline gives the essence of the problem in one or two sentences. After the headline comes the body of the problem. This is the longest section. It describes the empirical background of the pattern, the evidence for its validity, the range of different ways the pattern can be manifested in a building, and so on. Then, again in bold type, like the headline, is the solution—the heart of the pattern—which describes the field of physical and social relationships which are required to solve the stated problem, in the stated context. This solution is always stated in the form of an instruction—so that you know exactly what you need to do, to build the pattern. Then, after the solution, there is a diagram, which shows the solution in the form of a diagram, with labels to indicate its main components.

After the diagram, another three diamonds, to show that the main body of the pattern is finished. And finally, after the diamonds there is a paragraph which ties the pattern to all those smaller patterns in the language, which are needed to complete this pattern, to embellish it, to fill it out.

There are two essential purposes behind this format. First, to present each pattern connected to other patterns, so that you grasp the collection of all 253 patterns as a whole, as a language, within which you can create an infinite variety of combinations. Second, to present the problem and solution of each pattern in such a way that you can judge it for yourself, and modify it, without losing the essence that is central to it.

Let us next understand the nature of the connection between patterns.

It is quite possible that the collective cohesion people need to form a viable society just cannot develop when the vehicles which people use force them to be 10 times farther apart, on the average, titan they have to be. This states the possible social cost of cars in its strongest form. It may be that cars cause the breakpoints of society, simfly because of their geometry.

At the same time that cars cause all these difficulties, they also have certain unprecedented virtues, which have in fact led to their enormous success. These virtues are:

Flexibility

Privacy

Door-to-door trips, without transfer Immediacy

These virtues are particularly important in a metropolitan region which is essentially two-dimensional. Public transportation can provide very fast, frequent, door-to-door service, along certain arteries. But in the widely spread out, two-dimensional character of a modern urban region, public transportation by itself cannot compete successfully with cars. Even in cities like London and Paris, with the finest urban public transportation in the world, the trains and buses have fewer riders every year because people are switching to cars. They are willing to put up with all the delays, congestion, and parking costs, because apparently the convenience and privacy of the car are more valuable.

Under theoretical analysis of this situation, the only kind of transportation system which meets all the needs is a system of individual vehicles, which can use certain high-speed lines for long cross-city trips and which can use their own power when they leave the public lines in local areas. The systems which come closest to this theoretical model are the various Private Rapid Transit proposals; one example is the Westinghouse Starr-car—a system in which tiny two-man vehicles drive on streets locally and onto high-speed public rails for long trips.

However, the Starrcar-type systems have a number of disadvantages. They make relatively little contribution to the problem of space. The small cars, though smaller than a conventional car, still take up vastly more space than a person. Since the private cars will not be capable of long cross-country trips, they must be

IO56

. . . some of the doors in a building play a special role in creating transitions and maintaining privacy: it may be any of the doors governed by family of entrances (102), or main

ENTRANCE (lio), Or THE FLOW THROUCH ROOMS ( I 3 I ) Or CORNER DOORS ( 196) , Or NATURAL DOORS AND WINDOWS (22l).

*

This pattern helps to complete these doors by giving them a special height and shape.

*

High doorways are simple and convenient. But a lower door is often more profound.

The 6' rectangular door is such a standard pattern, and is so taken for granted, that it is hard to imagine how strongly it dominates the experience of transition. There have been times, however, when people were more sensitive to the moment of passage, and made the shape of their doors convey the feeling of transition.

An extreme case is the Japanese tea house, where a person entering must literally kneel down and crawl in through a low hole in the wall. Once inside, shoes off, the guest is entirely a guest, in the world of his host.

Among architects, Frank Lloyd Wright used the pattern many times. There is a beautifully low trellised walk behind Taliesin West, marking the transition out of the main house, along the path to the studios.

If you are going to try this pattern, test it first by pinning cardboard up to effectively lower the frame. Make the doorway low enough so that it appears “lower than usual”—then people will immediately adapt to it, and tall people will not hit their heads.

Therefore:

Instead of taking it for granted that your doors are simply 6' 8" rectangular openings to pass through, make at least some of your doorways low enough so that the act of going through the door is a deliberate thoughtful passage

1057

from one place to another. Especially at the entrance to a house, at the entrance to a private room, or a fire corner— make the doorway lower than usual, perhaps even as low as

Test the height before you build it, in place—natural doors and windows (221). Build the door frame as part of the structure—frames as thickened edges (225), and make it beautiful with ornament (249) around the frame. If there is a door, glaze it, at least partially—solid doors with glass (237). . . .

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225 FRAMES as thickened

EDGES**

^I0S9

. . . assume that columns and beams are in and that you have marked the exact positions of the doors and windows with string or pencil marks—natural doors and windows (221). You are ready to build the frames. Remember that a well made frame needs to be continuous with the surrounding wall, so that it helps the building structurally—efficient structure (206), GRADUAL STIFFENING (208).

•5* *5* *5*

Any homogeneous membrane which has holes in it will tend to rupture at the holes, unless the edges of the holes are reinforced by thickening.

The most familiar example of this principle at work is in the human face itself. Both eyes and mouth are surrounded by extra bone and flesh. It is this thickening, around the eyes and mouth, which gives them their character and helps to make them such important parts of human physiognomy.

A building also has its eyes and mouth: the windows and the doors. And following the principle which we observe in nature, almost every building has its windows and doors elaborated, made more special, by just the kind of thickening we see in eyes and mouths.

The fact that openings in naturally occurring membranes are invariably thickened can be easily explained by considering how the lines of force in the membrane must flow around the hole.

The increasing density of lines of force around the perimeter of the hole requires that additional material be generated there to prevent tearing.

Consider a soap film. When you prick the film, the tension pulls the film apart, and it disintegrates. But if you insert a ring of string into the film, the hole will hold, because the tensile forces which accumulate around the opening can be held by the thicker ring. This is in tension. The same is true for buckling and compression. When a thin plate is functioning in compression and a hole is made in it, the hole needs stiffening. It is important to recognize that this stiffening is not only supporting the opening itself against collapse, but it is taking care of the stresses in the membrane which would normally be distributed in that part of the membrane which is removed. Familiar examples of such stiffening in plates are the lips of steel around the portholes in a ship or in a locomotive cab.

The same is true for doors and windows in a building. Where the walls are made of wood planks and lightweight concrete fill—see wall membranes (218)—the thickened frames can be made from the same wood planks, placed to form a bulge, and then filled to be continuous with the wall. If other types of skin are used in the wall membranes, there will be other kinds of thickening: edges formed with chicken wire, burlap, and resin, filled with concrete; edges formed with chicken wire filled with rubble, and then mortar, plaster; edges formed with brick, filled, then plastered.

1061

More general examples of frames as thickened edges exist all over the world. They include the thickening of the mud around the windows of a mud hut, the use of stone edges to the opening in a brick wall because the stone is stronger, the use of double studs around an opening in stud construction, the extra stone around the windows in a gothic church, the extra weaving round the hole in any basket hut.

Therefore:

Do not consider door and window frames as separate rigid structures which are inserted into holes in walls. Think of them instead as thickenings of the very fabric of the wall itself, made to protect the wall against the concentrations of stress which develop around openings.

In line with this conception, build the frames as thickenings of the wall material, continuous with the wall itself, made of the same materials, and poured, or built up, in a manner which is continuous with the structure of the wall.

In windows, splay the thickening, to create deep reveals (223) ; the form of doors and windows which will fill the frame, is given by the later patterns—windows which open wide (236), SOLID DOORS WITH GLASS (237), SMALL PANES (239). . . .

as you build the main jrame and its openings _y put in the following subsidiary patterns where they are appropriate;

226. COLUMN PLACE

227. COLUMN CONNECTION

228. STAIR VAULT

229. DUCT SPACE

230. RADIANT HEAT

231. DORMER WINDOWS

232. ROOF CAPS

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1064

. . . certain columns, especially those which are free standing, play an important social role, beyond their structural role as columns at the corners (212). These are, especially, the columns which help to form arcades, galleries, porches, walkways, and outdoor rooms—public outdoor room (69), arcades (lI9), OUTDOOR ROOM (163), GALLERY SURROUND ( 166), SIX-foot balcony (167), trellised walk (174). This pattern defines the character these columns need to make them function socially.

♦ * •

Thin columns, spindly columns, columns which take their shape from structural arguments alone, will never make a comfortable environment.

The fact is, that a free-standing column plays a role in shaping human space. It marks a point. Two or more together define a wall or an enclosure. The main function of the columns, from a human point of view, is to create a space for human activity.

In ancient times, the structural arguments for columns coincided in their implications with the social arguments. Columns made of brick, or stone, or timber were always large and thick. It was easy to make useful space around them.

A big thick column.

But with steel and reinforced concrete, it is possible to make a very slender column; so slender that its social properties disap-

1065

I I LOCAL TRANSPORT AREAS

treated as a “second vehicle”—and are rather expensive. They make no contribution to the health problem, since people are still sitting motionless while they travel. The system is relatively antisocial, since people are still encapsulated in “bubbles” while they travel. It is highly idealistic, since it works if everyone has a Starrcar, but makes no allowance for the great variety of movement which people actually desire, i.e., bikes, horses, jalopies, old classic cars, family buses.

We propose a system which has the advantages of the Starrcar system but which is more realistic, easier to implement, and, we believe, better adapted to people’s needs. The essence of the system lies in the following two propositions:

r. For local trips, people use a variety of low-speed, low-cost vehicles (bicycles, tricycles, scooters, golf carts, bicycle buggies, horses, etc.), which take up less room than cars and which all leave their passengers in closer touch with their environment and with one another.

2. People still own, and use, cars and trucks—but mainly for long trips. We assume that these cars can be made to be quiet, nonpolluting, and simple to repair, and that people simply consider them best suited for long distance travel. It will still be possible for people to use a car or a truck for a local trip, either in a case of emergency, or for some special convenience. However, the town is constructed in such a way that it is actually expensive and inconvenient to use cars for local trips—so that people only do it when they are willing to pay for the very great social costs of doing so.

pear altogether. Four inch steel pipes or 6 inch reinforced concrete columns break up space, but they destroy it as a place for human action, because they do not create “spots” where people can be comfortable.

In these times, it is therefore necessary to reintroduce, consciously, the social purposes which columns have, alongside their structural functions. Let us try to define these social purposes exactly.

A column affects a volume of space around it, according to the situation. The space has an area that is roughly circular, perhaps 5 feet in radius.

\

I

*

\

M‘-

5 ’ ¹

The sface around the column.

When the column is too thin, or lacks a top or bottom, this entire volume—an area of perhaps 75 square feet—is lost. It cannot be a satisfactory place in its own right: the column is too thin to lean against, there is no way to build a seat up against it, there is no natural way to place a table or a chair against the column. On the other hand, the column still breaks up the space. It subtly prevents people from walking directly through that area: we notice

1066

that people tend to give these thin columns a wide berth; and it prevents people from forming groups.

In short, if the column has to be there, it will destroy a considerable area unless it is made to be a place where people feel comfortable to stay, a natural focus, a place to sit down, a place to lean.

Therefore:

When a column is free standing, make it as thick as a man—at least 12 inches, preferably 16 inches: and form places around it where people can sit and lean comfortably: a step, a small seat built up against the column, or a space formed by a pair of columns.

You can get the extra thickness quite cheaply if you build the column as a box column (216); complete the “place” the column forms, by giving it a “roof” in the form of a column capital, or vault which springs from the column, or by bracing the column against the beams-—column connection (227). And when it makes sense, make the column base a sitting wall (243), a place for flowers—raised flowers (245), or a place for a chair or table-DIFFERENT CHAIRS (25 1). . . .

227 COLUMN CONNECTIONS**

. . . the columns are in position, and have been tied together by a perimeter beam—box columns (216), perimeter beams

(217). According to the principles of continuity which govern the basic structure—efficient structure (206), the connections need stiffening to lead the forces smoothly from the beams into the columns, especially when the columns are free standing as they are in an arcade or balcony—arcade ( i i 9), gallery surround (166), SIX-FOOT BALCONY (167), COLUMN PLACE (226). You may also do the same in the upper corners of your door and window frames—frames as thickened edges (225)—making arched openings.

•5*

The strength of a structure depends on the strength of its connections; and these connections are most critical of all at corners, especially at the corners where the columns meet the beams.

There are two entirely different ways of looking at a connection:

1. As a source of rigidity, which can be strengthened by triangulation, to prevent racking of the frame. This is a moment connection: a brace. See the upper picture.

2. As a source of continuity, which helps the forces to flow easily around the corner in the process of transferring loads by changing the direction of the force. This is a continuity connection: a capital. See the lower picture.

x. A column connection as a brace.

As a building is erected, and throughout its life, it settles, creating tiny stresses within the structure. When the settling is uneven, as it most always is, the stresses are out of balance; there is strain in every part of the building, whether or not that part of the building was designed to accept strain and transmit the forces on down to the ground. The parts of the building that are not designed to carry these forces become the weak points of the building subject to fracture and rupture.

Effects of uneven stresses on a frame.

Rectangular frames, especially, have these cracks at the corners because the transmission of the load is discontinuous there. To solve this problem the frame must be braced—made into a rigid frame that transmits the forces around it as a whole without distorting. The bracing is required at any right-angled corner between columns and beams or in the corners of door and window frames.

2. A column connection as a capital.

This happens most effectively in an arch. The arch creates a continuous body of compressive material, which transfers vertical forces from one vertical axis to another. It works effectively because the line of action of a vertical force in a continuous compressive medium spreads out downward at about 45 degrees.

And a column capital is, in this sense, acting as a small, underdeveloped arch. It reduces the length of the beam—and so reduces bending stress. And it begins to provide the path for the forces as they move from one vertical axis to another, through the medium of the beam. The larger the capital, the better.

A capital that acts the same vuay as an arch.

A column connection will work best when it acts both as a column capital and as a column brace. This means that it needs to

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227 COLUMN CONNECTIONS

be thick and solid, like a capital, so that there is a lot of material for the forces to travel through, and stiff and strong and completely continuous with the column and perimeter beam, like the brace, so that it can work against shear and bending.

The bone structure, shown below uses both principles, to transfer compressive stress from one strut to another, continuously, throughout a three-dimensional space frame of struts. The structure is most massive at the connections, where the forces change direction.

A similar column connection can be made integral with poured hollow columns and beams. The forms for the connection are gussets made of skin material: then fill the column and the gussets and the beam in a continuous concrete pour.

Of all the patterns in the book, this is one of the most widespread and has taken the greatest variety of outward forms throughout the course of history. A solid wood capital on a wood column, or a continuously poured column top, and arches of stone, brick, or poured concrete are all examples. And, of course, typical column capitals—a larger stone on a stone column or typical gusset plate or brace—even if weak in some ways, also help a great deal. But only relatively few of the historical column connections succeed fully in acting both as braces and as capitals.

Therefore:

Build connections where the columns meet the beams. Any distribution of material which fills the corner up will do: fillets, gussets, column capitals, mushroom column, and

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most general of all, the arch, which connects column and beam in a continuous curve.

The connection is one of the most natural places for ornament (249): there is a wide variety of possible connections, carvings, fretwork, painting, for this critical position. In certain cases, the connection may act as an umbrella for a column place (226). . . .

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. . . this pattern helps complete the rough shape and location of stairs given by staircase as a stage (133) and by staircase volume (195). If you want to build a conventional stair, you can find what you need in any handbook. But how to build a stair in a way which is consistent with the compressive structure of efficient structure (206), without using wood or steel or concrete—good materials (207) ?

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Within a building technology which uses compressive materials as much as possible, and excludes the use of wood, it is natural to build stairs over a vaulted void, simply to save weight and materials.

A concrete stair is usually made from precast pieces supported by steel stringers; or it is formed in place, and then stripped of its forms. But for the reasons already given in good materials (207), precast concrete and steel are undesirable materials to use—they call for modular planning; they are unpleasant materials to touch, look at, and walk on; they are hard to work with and modify in any relaxed way, since they call for special tools.

Given the principles of efficient structure (206), good MATERIALS (2O7), and GRADUAL STIFFENING (208), We suggest that stairs be made like floor-ceiling vaults (219)—by making a half-vault (to the slope of the stair), with lattice strips, burlap, resin, chickenwire, and lightweight concrete. The steps themselves can then be formed by using wood planks, or tiles, as risers, and filling in the steps with trowelled concrete.

When we first wrote this pattern, we thought it was very doubtful-—and put it in mainly to be consistent with floor and roof vaults!, Since then we have built a vaulted stair. It is a great success —beautiful—and we recommend it heartily.

Therefore:

Build a curved diagonal vault in the same way that you

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228 STAIR VAULT

build your floor-ceiling vaults (219). Once the vault hardens, cover it with steps of lightweight concrete, trowel-formed into position.

A lightweight concrete tread, colored, waxed, and polished can be quite beautiful and soft enough to be comfortable—see floor surface (233)—and will eventually take on the patina of wear called for in soft tile and brick (248).

The vaulted space under the stair can be used as an alcove (179) a child cave (203), or closets between rooms (198). If it is plastered, like a regular ceiling—see floor-ceiling vaults (219), it makes a much more pleasant and useful space than the space under an ordinary stair.

TOWNS

Therefore:

Break the urban area down into local transport areas, each one between i and 2 miles across, surrounded by a ring road. Within the local transport area, build minor local roads and paths for internal movements on foot, by bike, on horseback, and in local vehicles; build major roads which make it easy for cars and trucks to get to and from the ring roads, but place them to make internal local trips slow and inconvenient.

To keep main roads for long distance traffic, but not for internal local traffic, lay them out as parallel one way roads, and keep these parallel roads away from the center of the area, so that they are very good for getting to the ring roads, but inconvenient for short local trips—parai.lel roads (23). Lay out abundant footpaths and bike paths and green streets, at right angles to the main roads, and make these paths for local traffic go directly through the center—green streets (51), network of paths and cars (52), bike paths and racks (56); sink the ring roads around the outside of each area, or shield the noise they make some other way—ring roads (17); keep parking to a minimum within the area, and keep all major parking garages near the ring roads— NINE PER CENT PARKING (22), SHIELDED PARKING (97) i and build a major interchange within the center of the area—interchange (34). . . .