Fig. 16 (b). Geometry of roof intersection
assemble a variety of different types of houses, ranging from extremely small ones such as that shown in Fig. 14 to buildings of virtually unlimited size and complication; one of the larger models is shown under construction in Fig. 15, taken during the early stages of the experimental work. At the beginning of the scheme, however, only small houses will be considered since the provision of accommodation for the poorest section of the population was the original aim of the design.
The new design in its present form will give a decidedly lower class of construction than the Housing Trust designs already considered. Cor- rugated metal is proposed for the roofs instead of asbestos cement, and smaller timber sections are used. But the timber will be pressure- impregnated with preservative after all machining operations have been completed. and an indefinitely long life will be assured in the parts of the structure that are kept per- manently dry.
The principle of the construction was invented by the Timber Research Laboratory of the Malayan Forest Department's research institute. The staff concerned had negligible ex- perience of traditional building practice, and set out to discover a system of construction which would satisfy certain theoretical require- ments. The first of these can be illustrated briefly by reference to Fig. 16. If the "traditional" shape shown by the drawing is to be built up with
minimum number of standard frames, each of which can form either a wall section or a roof section, the portions ABCD and EFGH should be congruent. The only roof pitch that allows this is 38.2°. However, there are other advantages in having a roof pitch of
44
a
Fig. 16 (a). Determination of minimum number of parts to construct traditional type of house exterior.
Fig. 17.
A selection of shapes formed by the basic construction units. 36.9° instead, yielding a triangle with sides in the ratio 3:4:5. Since this angle is only 1.3° different from 38.2°, it was supposed that the triangular shapes could be made with an angle of 36.9° and that the effect of the slightly "wrong" value would be merely to introduce minor distortions at unimportant points in the roof structure. Fullscale experi- ments have since shown this position to be correct.
sup-
Fig. 17 gives an idea of the great variety of buildings that can theore-
tically be formed by assembling squares, triangles of the shape just described, and rectangular frames of 2 ft. width to form the wall and roof sections; some of the buildings require an additional rectangular shape if the floors are also to be built from the same standard
up frames as the walls and roof. The theoretical solution of the problem allows two triangles to be fastened together to form a rectangle of 8 ft. x 6 ft., and long walls have to be built up from a number of squares and rectangles. In the practical
THE HONG KONG & FAR EAST BUILDER — VOLUME 15, NUMBER 1