Flashing is one of the elements of a well-built house that doesn't draw much attention until it goes bad, as it's often known to do (there are a number of reasons for this that we'll discuss below). If you think you've found the right property in your search for a new home, you should be aware of the condition (or non-existence) of the critical flashing that's designed to prevent water penetration and the resulting, and frequently costly, structural damage it can cause. It's one of countless reasons to make sure you have a home inspection before purchasing a home that could end up hitting your bank account in unexpected ways.
How important is proper flashing? Very important. Ask experienced inspectors and builders and they'll tell you that the majority of roof leaks occur due to failed flashing, with some experts noting that more than 90% of all roof leaks are related to the quality of the flashing (more conservative estimates place the number at 75%, but it's a major issue either way).
For the next couple of blog posts, we'll be focusing on problems associated with various kinds of flashing found in a roofing system, where angle changes, vertical wall/roof intersections, and penetrations such as chimneys, skylights, dormers, and plumbing vents protruding from the roof make certain areas vulnerable to moisture getting inside. Varieties of fabricated sheet-metal roof flashing include step, counter, valley, pan, and kickout types. An experienced inspector will be able identify defects typical with the specifications of each variety. It must be noted that there will be instances in which roof flashing is hidden and cannot be inspected (mention of this limitation will appear in the home inspection report).
When evaluating a home, the inspector may notice interior wall and ceiling stains or active leaks that will raise serious raise flags that there are issues up above. Here are some of the issues that the inspectors at a-pro have found after inspecting many thousands of roofs over the last 27 years:
Corrosion: In drastic cases, corroded flashing (galvanized steel, copper, lead, et. al.) can contribute to water leaking into a home. Your inspector will note the presence of corroded flashing and the level of severity, from moderate to severe conditions where the flashing is no longer doing its job of preventing moisture penetration and diverting water toward the gutter system. Your inspector will be on high alert if you live in a region with a climate that makes corroded flashing more common. They will also be aware of the expected lifespan of properly installed flashing based on the materials used.
Installation Defects: When it comes to doing flashing correctly, amateurs need not apply. A-Pro inspectors have seen their fair share of poor flashing installations and shoddy repair jobs that make matters even worse. Because there are a number of methods for installing flashing, your inspector's primary concern during this portion of the inspection, as reported by the International Association of certified home inspectors, is to make sure flashing is installed in a manner that will keep rain and melting snow/ice from finding its way inside.
For example, gaps beneath headwall flashing will be highlighted since they can provide easy access for wind-driven rain. Another common concern is the use of sealants in lieu of flashing—a situation that will eventually allow water penetration as the material shrinks and cracks. Sealant is commonly found incorrectly employed instead of flashing (with recommended counter flashing) when brick and stone walls are involved. Your inspector will note any gaps in failed sealants. In extreme cases, counter flashing will be missing entirely.
A frequent problem with step flashing (a requirement for asphalt, slate, and wood shingle manufacturers at sidewalls) is use of continuous, one-piece flashing rather than the multiple pieces of short flashing that comprise a proper installation. When possible, your inspector will check to make sure that step flashing is properly extended up behind the exterior wall covering and that it has the necessary overlapping pattern to shed water. Tile roof coverings require continuous pan-type flashing, but this is often difficult to confirm. While checking sidewall/headwall flashing, your inspector may note that wall covering and roof covering are in direct contact—a condition that can lead to material decay. A clearance of at least 1-1/2 inches between wall covering and roof covering is recommended.
Other defects include missing kickout flashing that should have been installed where the flashing ends to prevent rainwater from entering behind the wall covering; highly vulnerable open roof valleys that have missing flashing or have been flashed with a material other than metal; loose, poorly fastened, misaligned, improperly bent, wrongly sized, or missing flashing pieces; use of incompatible materials; and use of roofing tar in place of flashing. Your inspector may indicate the presence of standing water on flashing, which may cut short its useful life.
In our next post, we'll be looking at common flashing defects associated with chimneys and other roof penetrations.