A pattern language

We also know, from sheltering roof (117), that entire wings should be under one roof whenever possible and that the building is to be roofed with a mixture of flat roofs and sloping or domical roofs, with the accent on those which are not flat.

We may therefore state the problem of defining a roof layout as follows: Given an arbitrary flan of the tyfe described above, how can we fit to it an arrangement of roofs which co?iforms to the cascade of roofs (r/d) and sheltering roof (117) and

ROOF GARDENS (Il8)?

Before explaining the procedure for laying out roofs in detail, we underline five assumptions which provide the basis for the procedure.

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CONSTRUCTION

I. The “pitched” roofs may actually be pitched, or they may be vaults with a curved pitch, or barrel vaults—as described in roof vaults (220). The general procedure, in all three cases, is the same. (For curved vaults, define slope as height-to-width ratio.)

The “fitch” of a vaulted roof.

2. Assume that all roofs in the building, which are not flat, have roughly the same slope. For a given climate and roof construction, one slope is usually best; and this greatly simplifies construction.

The same slope throughout.

3. Since all roofs have the same slope, the roofs which cover tire widest wings and/or rooms will have the highest peaks; those covering smaller wings and rooms will be relatively lower. This is consistent with main building (99), cascade of roofs

(1 16), and CEILING HEIGHT VARIETY (190).

Wide roofs are highest.

4. Any place where the building helps to enclose an outdoor room or courtyard needs an even eave line so that it has the space of a “room.” An irregular roof line, with gable ends, will usually destroy the space of a small courtyard. It is necessary, therefore, that roofs be hipped in these positions to make the roof edge horizontal.

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209 ROOF i.ayout
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Lo<w roof edge round a courtyard.

5. In all other positions, leave the ends of buildings and wings as gable ends.
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CONSTRUCTION

We shall now discuss the rules for roofing a building by using an example of a house designed by a layman using the pattern language. This building plan is shown below. It is a single-story house and it contains no roof gardens or balconies.

We first identify the largest rectangular cluster of rooms and roof it with a peaked roof, the ridge line of which runs the long direction:

Then we do the same with smaller clusters, until all the major spaces are roofed.

Then we roof remaining small rooms, alcoves, and thick walls with shed roofs sloping outward. These roofs should spring from the base of the main roofs to help relieve them of outward thrusts; their outside walls should be as low as possible.

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209 ROOF layout

Finally, we identify the outdoor spaces (shown as A, B, and C), and hip the roofs around them to preserve a more continuous eave line around the spaces.

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We shall now discuss a slightly more complicated example, a two story building.

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We begin with the top story, roofing the entire master bedroom and bath under one peaked roof with the ridge running lengthwise:

Next we move to the lower story, roofing the children’s wing under a flat roof to form a roof garden ( i i 8) for the master bedroom, and the larger living room under a pitched roof, again with the ridge running lengthwise.

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10 MAGIC OF THE CITY

58

CONSTRUCTION

Then we bring the roof over the master bedroom down over the interior loft.

Finally, we smooth the living room roof ridge line into the side of the roof over the loft. This completes the roof layout.

It is very helpful, when you are laying out roofs, to remember the structural principle outlined in cascade of roofs ( i i6). When you have finished, the overall arrangement of the roofs should form a self-buttressing cascade in which each lower roof helps to take up the horizonal thrust generated by the higher roofs—and the overall section of the roofs, taken in very very general terms, tends toward a rough upside down catenary.

Therefore:

Arrange the roofs so that each distinct roof corresponds to an identifiable social entity in the building or building complex. Place the largest roofs—those which are highest and have the largest span—over the largest and most important and most communal spaces; build the lesser roofs off these largest and highest roofs; and build the smallest roofs of all off these lesser roofs, in the form of half-vaults and sheds over alcoves and thick walls.

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209 ROOF LAYOUT

major roofs

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You can build all these roofs, and the connections between them, by following the instructions for roof vaults—roof vaults (220). When a wing ends in the open, leave tire gable end at full height; when a wing ends in a courtyard, hip the gable, so that the horizontal roof edge makes the courtyard like a room— COURTYARDS WHICH LIVE ( I I 5) .

Treat the smallest shed roofs, which cover thick walls and alcoves, as buttresses, and build them to help take the horizontal thrust from floor vaults and higher roof vaults—thickening the OUTER WALLS ( 2 I I ) . . . .

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210 FLOOR AND CEILING

LAYOUT

. . . efficient structure (206) tells us that the spaces in the building should be vaulted so that the floors and ceilings can be made almost entirely of compression materials. To lay out the floor and ceiling vaults, we must fit them to the variety of ceiling heights over individual rooms—ceiling height variety (19°) and, on the top story, to the layout of the roof vaults—roof layout (209).

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Again, the basic problem is to maintain the integrity of the social spaces in the plan.

We know, from structure follows social spaces (205), that floor and ceiling vaults must correspond to the important social spaces in the plan. But there are a great number of social spaces, and they range in size from spaces like window place (180), perhaps five feet across, to spaces like farmhouse kitchen (¹ 39), perhaps 15 feet across, to collections of spaces, like common areas at the heart (129), perhaps 35 feet across.