In Part 1 of our series on the importance of roof flashing, we looked at some general defects (corrosion; and loose, missing, damaged, and misaligned pieces); poor installation practices; and issues with step, headwall, sidewall, and valley flashing. Today, we turn our attention to flashing for a masonry-constructed chimney, one of the most common areas of roof leakage. We’ll also be checking out frequent flashing problems with skylights, vent pipes, and dormer windows.
The headwall and sidewall flashing used on walls that we discussed last week is similar to the flashing used for a stone or brick chimney. Even before doing an evaluation of the chimney, your home inspector may have a pretty good idea that there are flashing issues above by noting ceiling stains in the vicinity of the chimney’s location in the attic. Once on the roof—if roof accessibility is possible or other means of observation is available—further evidence of failed flashing may include deteriorated roof sheathing around the chimney and warped shingles adjacent to the penetration.
There are a number of factors that can lead to chimney flashing damage, including the normal aging process; application of tar over metal flashings; foundational shifting that may pull flashing away from the structure; corrosion of the metal (typically galvanized steel, aluminized steel, lead, copper, or lead-coated copper) sometimes attributed to installations using incompatible materials, such as aluminum and brick; the freeze-thaw cycle that may leave gaps in the flashing, though it’s not a condition your inspector will be able to pinpoint; unprofessional installations that don’t provide an adequate, longtime watertight seal around the chimney; damage from animals; decay of fasteners; and mortar deterioration.
As we noted in our previous blog post, hiring an experienced roofer with a good track record of quality flashing installations is an important step to avoid problems down the road. Similarly, an experienced inspector will be able to recognize a proper installation, as well as those that don’t measure up. The certified home inspectors at A-Pro have seen the good, the bad, and the ugly when it comes to flashing at the chimney and other locations. Here are just a few of the defects they have observed over 27 years of performing foundation-to-roof inspections:
Counter (Cap) Flashing Issues: The chimney requires a combination of step, or base flashing, and bottom, side, and top counter flashing that fit into cuts in mortar joints and cover the base to prevent water penetration. When inspecting the chimney, your inspector will first check to see that all pieces are in place and if they’re properly secured, ensuring that all the thin metal parts are positioned correctly and extend as necessary to block moisture intrusion. Especially with complicated installations, such as may occur with a stone chimney, the use of a sealant rather than metal counter flashing is a frequent, easier-to-execute, less costly, and far inferior solution that is commonly used, as sealants are prone to shrink and crack. Your inspector may recommend that such an installation be regularly monitored to ensure that the sealant is still effective. The inspector may find an excessive amount of tar in the installation—a possible indication of a cheaply done leak repair job. In extreme cases, the installation will have no counter flashing at all, which will be highlighted by your inspector.
Chimney Cricket or Saddle: This device abuts a chimney to help shed water from the top side in cases where a chimney has a broad width or is close to a valley or other barrier. The lack of a cricket (or, alternatively, longer-extending top cap flashing) increases the chance of water accumulating against the chimney, possibly leading to damage and leakage.
Plumbing Vents: One of the easier issues for an inspector to spot is an improperly flashed plumbing vent poking through the roof. The inspector will check to see if the pipe has an undamaged rubber boot at its base, which is used to prevent water penetration. Caulking applied around the pipe is not considered adequate to prevent rainwater from entering the roof structure.
Skylights: Proper flashing is critical to prevent skylights from leaking. Your inspector will check to see if there is adequate flashing in place and that it is still functional. Ceiling and wall stains in the room below the skylight may present evidence of past leakage.
Window Dormers: The addition of dormers can add unique charm and an infusion of sunlight to a home, but they also can present a bevy of leaking issues when improper roof-to-wall and roof-to-valley flashing has been installed. As with skylights, ceiling stains in the room below a dormer will alert a home inspector that failed flashing (step flashing, in this case) may be an issue or that no flashing was included in the installation. In some instances, step flashing may have been installed without counter flashing. Further, your inspector may find flashing missing at the top of the trim over the window. We’ll be looking at the importance of window flashing in our next post.
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