CASE STUDY

Southern California is known for having a mild climate; however, it also has extremes and potential hazards for buildings. Near the ocean, the climate is wet and humid, while inland the climate is hot and dry. In the winter and late spring, these two climates tend to collide, causing dense fog in the morning and dry hot temperatures in the evenings. These wet and dry cycles can wreak havoc on outside structures, and the effects often can be seen on trees, street signs, lampposts, and building exteriors.

Challenge: A homeowner in California began to notice a few small cracks in his stucco several months after construction. Over time, the cracks expanded and grew. Within a year, it was obvious that the building structure had some serious problems. The homeowner called his architect, who was unable to determine the source of the problem. The lath installer, stucco contractor, waterproofer, and window installer all were stumped and confirmed that they had properly installed each component of the structure, and that they each followed codes and protocols.

Problem: Building science expert Barry Taheri, a professional deeply familiar with complete wall systems, was called in to determine the underlying problem. Barry and his team began investigating the structure, working their way from the outer finish coat of the stucco all the way through the wire, paper, fasting, and sheathing. He discovered that the wall in question was built without the grooved paper that provides draining capacity that the wall needed. Had the entire structure been made of walls without openings for windows or doors, this wouldn’t have been a problem. However, the wall had windows and doors that were not sealed well enough to offset the poor drainage capacity. In this case, the contractors who built the wall assumed that the windows and doors would be sealed well enough to offset poor drainage, while the window installers assumed the wall had been built to drain well.

A few miles inland, in the dry, arid climate, this wouldn’t have been a problem for the building structure at all. But on the coast, where there are cycles of wet and dry conditions, the moisture content increased, the wood swelled, and the stucco cracked, which allowed more moisture in.

Prevention: As discussed in the first section of this course, the building envelope must be treated like a complete system. If all areas aren’t properly sealed against the elements, water can seep in and destroy the building structure from the inside out. In the stucco home example, the homeowner was forced to rip out the stucco, windows, doors, weather barriers, and everything right down to the sheathing substrate. It all had to be redone, costing more than $60,000 in repairs and creating legal disputes between the homeowner and contractors.

This disaster could have been prevented with a mere $700 worth of quality sealant properly applied around the fenestrations during installation.