For about five years I worked at two different firms that specialized in repairs to building defects. Some of these failed buildings were architectural beauties, and others dogs. Repairs needed included roofing, flashing, siding, structural, concrete spalling, lead and asbestos abatement, buried membrane failures, etc. Sometimes a 'mystery leak' confounded contractors and previous repair efforts. Condominiums were the most dangerous. A small overlooked design or construction detail repeated hundreds or thousands of times over multiple units adds up to expensive lawsuits.
Days apart I had site visits to both Potrero Terrace of San Francisco Public Housing gangland fame and the private residence of a San Francisco real estate developer at the top of Lombard Street. Water damage did not discriminate based on building aesthetics, or on the money one had. Both projects had water leaks and resultant damage resulting from age related material failure. A building owner can spend more money on durable materials up front and usually save money in the long run, but all buildings will fail eventually. Correct design and installation buys more time.
In building design there are high maintenance building assemblies and low maintenance more durable building assemblies. For one example, the joint between wood trim above windows and siding can be caulked, or a metal 'z' flashing installed to shed water away from this joint. The sealant joint will require regular maintenance which can be performed when painting the building, but even the best caulk is only as good as the surface it is adhered to. The metal 'z' flashing is initially more expensive, but eliminates the recurring cost to caulk this joint. The metal flashing is less likely to fail during the lifespan of the siding and cause damage to the structure. Suitability and lifespan of materials, expectation of proper installation, probability of maintenance all are evaluated for every building material, product and assembly.
Often building failures are the result of misplaced priorities. I have argued with contractors and developers to install 20 cent/lineal foot metal 'z' flashing on million dollar homes, while interior decorators have no problem getting the budget to upgrade kitchen counters from imported Indian granite to French limestone. Limestone counters sell, while flashing goes unnoticed and unappreciated.
Other times a building will fail because of misplaced efforts caused by a poor understanding of building science. On one large condominium project, the contractor was instructed to install sealant at window frame to sill and jamb trim joints, and not install sealant at window frame to head trim joints. Of course, the head trim was sealed to the frame too, trapping any moisture that could accumulate behind the trim and siding from weeping out through this joint. This unneeded caulking was wasted time and materials for the sealant subcontractor, who also had to remove it.
