Chimney Flashing Leaks
Smart Inspector Science
When Leaks Occur in “Perfect” Chimney Flashing
Roofs never leak – only roof penetrations and flashings leak, right? We check masonry chimneys and their flashings as part of an overall inspection, but flashing can be tricky.
“Perfect” masonry chimneys and flashings can leak
I inspected this great-looking newer chimney on a windy, rainy day (photo – Wet Masonry Chimney).
The chimney cap looked great; it hung over the brick chimney with a drip edge. There was a saddle behind the chimney at the upper roof. The clay tiles were capped with a stainless steel rain cap. The masonry was newer, and the mortar joints were tight. The chimney was wet on one side from the wind and rain.
The flashing on the lower roof was typical (photo – Wet Masonry Chimney Flashing).
Where the chimney penetrated the lower roof, counterflashing was visible but step flashing was not. Counterflashing was set against the masonry and caulked to the brick and mortar – this is typical in my area, though not ideal. Counterflashing should be cut into the masonry (illustration R081) to keep water from flowing through the porous surfaces.
Without the cut or “reglet” into the masonry joint or masonry, water can move behind the flashing through the porous masonry. This can cause a leak below.
Whoops! This great-looking flashing leaks
Significant, active leaks appeared in the unheated sun-room below the chimney (photo – Masonry Chimney Interior Leak). Water ran down the masonry surface. I never would have seen this if it was not raining and windy outside during my inspection.
What should you inspect?
Always look below the chimney exterior surface and around the wood framing near the chimney. In an older home, you’ll often notice stains. You should note these as indications of a potential issue. In many cases, a small leak around a chimney just evaporates, leaving no real damage.
If counterflashing is not cut into the masonry (reglet), my inspection report includes a standard note that this detail of poor construction will require maintenance and will be prone to leaks. The sealant or caulk will need routine maintenance and the joint may leak.
Always check ceilings and other interior finishes adjacent to the chimney. Water stains, or patching and fresh paint that might be hiding stains, should be noted for further evaluation. And obviously, extensive stains, ceiling damage, buckets and plastic sheeting around a chimney are red flags of a serious issue that needs further evaluation.
Tom Feiza has been a professional home inspector since 1992 and has a degree in engineering. Through HowToOperateYourHome.com, he provides high-quality marketing materials that help professional home inspectors educate their customers. Copyright © by Tom Feiza, Mr. Fix-It, Inc. Reproduced with permission.
R081 – Flashing – Fastening to Masonry Options
Photo – Wet Masonry Chimney
Photo – Wet Masonry Chimney Flashing
Photo – Masonry Chimney Interior Leak