Maintainable, multi-element external boundaries

The purpose of external boundaries is to protect the space from the uncontrollable variability of the external environment. To do so it must be constructed such that the component elements can both be renewed when necessary and locked together to render the boundary impervious.

The main function of the outside wall of a building is to keep the weather out. This can best be done with construction elements that lap together but can be repaired individually in patches as necessary. This is not possible with sheets of impervious material which can only be joined together with difficulty.