Common Durability Issues

Durability must be considered at all phases of a building’s life cycle, from the design phase (the focus of this course) to field installation and then to the long-term maintenance of a home. While a home’s builder and designer cannot always assure that durability-enhancing practices will be upheld “downstream” with contractors and homeowners, many of the most common durability issues can be positively affected by the builder and designer through selecting appropriate products, calling out key details on plans, and applying integrated design.

So what are these “common durability issues”?

According to the home inspection industry,3 these problems are among the “top 10” of home inspection issues:

• The landscape slopes toward the house (see Figure 2–1).
• Lack of proper exterior water control, e.g., gutters and downspouts.
• Bathroom vents exhaust into the attic.
• Lack of weep holes in brick, stone veneer and weep screed in stucco.
• Lack of and/or improper deck flashing.
• The furnace, air conditioner, fireplace, and/or dryer vent have not been serviced in the past 12 months
• Mortar missing in between the brick/stone of exterior chimney.

Thus, 7 of the 10 most common home inspection issues have direct durability implications!

Key durability-related findings from a survey of code officials conducted jointly by the National Association of Home Builders (NAHB) and the International Code Council (ICC) include:

• Among grading/site drainage code provisions, inadequate grading and downspout/draining controls were two of the three most common code violations
• In the area of flashing, window flashing problems were the most common area for code violations (see Figure 2–2). Further, code officials responded that 66% of the flashing problems were related to installation, as opposed to the product itself or both the product and the installation. This is actually an improvement; in the original 2006 study, 82% of code officials felt that flashing violations were primarily installation-related.

These results on durability-related code provisions are further evidence of commonly occurring issues. And considering that the building code doesn’t give us all of the durability measures to ensure good performance, getting the code provisions right is just a starting point.

Field surveys of older and newer homes also reveal both problems and some useful “lessons learned” for improved durability. In a 2001 durability assessment sponsored by U.S. HUD,4 findings included:

• Foundation Materials & Methods: In field assessments of 1970s and 1990s houses (homes that were roughly 25 years and 5 years old at the time of the study), 57% and 78% had basement foundations, respectively. In addition, 51% of the 1970s basement foundations used block construction whereas 73% of the 1990s basement foundations used concrete. While age is a factor in developing foundation cracks, 65% of the block foundations experienced visible cracking while only 10% of the concrete foundations exhibited similar cracks. Furthermore, 28% of the sites with surface depressions next to the foundation (commonly due to poor backfilling practices and settlement over time) accounted for 44% of the sites with visibly cracked foundation walls.
  
  • Lesson learned: Build a strong foundation and ensure proper backfill compaction and surface water drainage.
• Roof Overhangs: While only 40% of 1970s homes had roof overhangs of 12” or less, 82% of the 1990s homes fell into this category.
  • Lesson learned: A trend toward less roof overhang coupled with greater frequency of two-story construction in newer homes is leading to less protection of wall assemblies from rainwater intrusion. Greater attention to the proper execution of water-resistive barrier and flashing practices is important to offset the durability consequences of this trend.

Clearly, there are a wide range of durability problems in America’s homes. And while moisture is certainly the dominant driver of durability issues, other factors such as insects, sunlight, and mechanical system performance can also make or break a home’s durability over time. Thus, the chapters which follow have a strong emphasis on moisture and also take into account the other major durability drivers.