February, 2019

Inspection News and Views from the American Society of Home Inspectors

When Leaks Occur in “Perfect” Chimney Flashings


Roofs never leak—only roof penetrations and flashings leak, right? We check masonry chimneys and their flashings as part of an overall inspection, but flashings can be tricky. 

“Perfect” masonry chimneys and flashings can leak.
I inspected this great-looking newer chimney on a windy, rainy day. 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. 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—although not ideal, this is typical in my area. 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 sunroom below the chimney. Water ran down the masonry surface. I never would have seen this during my inspection if the weather had not been rainy and windy. 

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), I include a standard note in my inspection report 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 presents technical, educational sessions for home inspectors. To invite him to share his knowledge at your chapter’s next educational event, contact him at Tom@HTOYH.com.