Why is stability of a wooden prefab structure so important
Horizontal stability of a wooden prefab structure (thus also prefab houses) is always a main issue. Due to the fact that timber inter-connections do not fit exactly (like steel connections do), the structure is extremely sensitive for horizontal movements (displacements). It is not so difficult to horizontally move a wooden framework by hand, unless proper bracings are provided.
While earthquakes are of minor concern for a wooden house due to flexibility of the wooden structure, the same flexibility is of major concern when a hurricane or a cyclone strikes. The inter-connecting timber parts shall not only be strong enough to absorb the immensely high wind loads, the stability of the house is most important. The high wind pressure loads can easily be absorbed by the tropical hardwoods that we use, however the strength of a wood species does not contribute at all to overall stability. To accomplish this, additional and sometimes far-reaching measures need to be taken (which unfortunately has a negative impact on the price of the house). The second area of concern is the roof structure. Most people believe that it is the wind pressure which may disintegrate a roof. This is a misconception. It is the wind suction which does the major damage. Our engineers have a vast experience in dealing with these problems and know how to solve this.
All wooden prefab structures are normally subject to significant shrinkage and expansion caused by temperature and hunidity changes, which are far higher than those experienced for prefabricated concrete structures and prefabricated steel structures. The shrinkages and expansions in wood may have a significant impact on the connections, whether this is done with bolts or screws. These constant shrinkages and expansions will cause "slackening" of the connections, whereas unexpected and dangerous connection instabilities will occur, which may induce sudden collapses. Modern engineering techniques have been developed and codes been issued over the last decade which take such "slackening" phenomena into account. The codes provide formulae and design advice to cope with these aspects, arriving at safe connections which will remain safe over time. Our engineers are very well familiar with these codes and will properly apply them.
CONCLUSION: Relying on only the strength of the materials is not sufficient. An proper analysis on the overall stability and the connections shall equally be carried out.