The longevity of the entire building may, for example, hinge on how accommodating it is to new Services technology, especially in commercial buildings. The principle may even be applied to distinguish elements within the different levels which, depending on the building, may need more frequent maintenance or replacement: for example, elements of the building skin that are more exposed to weather, or components of the structure that are more likely to be changed to accommodate additions. Good design takes into account how the slower and quicker changing elements in a building influence each other. The slow partssite and structureconstrain and control the quick, as they express long-term trends. But especially in times of rapid change, the quicker (like electronic equipment) can influence the slower elements (like services or even structure). An appreciation of shearing layers affects all kinds of decisions about building design, especially choice of materials. For example, in Brands opinion slab-on-grade foundations, with services buried in the concrete and no basement storage space, are unwise. Because wood decays, wood structures are also not desirableexcept for timber frame, since its wood is massive, usually exposed (therefore well-ventilated), and well separated from services. Wood is not desirable on roofs, but is a good choice for siding, since (compared to, say, vinyl) wood breathes, shows its wear in an obvious way, and is repairable piecemeal. The notion of shearing layers has a social side as well. Truly adaptive building design not only puts the emphasis on building use and the needs of building users, but, because these needs are always somewhat unpredictable, the design has to allow users to shape the building to their needs. This is completely different from mainstream design