Ask the Architect

Our roof keeps on leaking

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Q. I’m writing about my flat roof leak. Please find enclosed photos of the inside and outside of my home. Since we bought it in 1975, we’ve been having trouble with the flat part of the roof. I’ve had the inside repaired, only to have it leak again. A couple of years ago, I had a new roof installed, mainly to fix the flat section. The roofers tarred the flat section. When I called them back a few months later to tell them it was leaking again, they just put a heavier coating of tar on it. After that didn’t work, they said there was nothing more they could do. I’ve called other leak finders, only to get no satisfaction. As you can see, the inside ceiling looks horrible. Outside, everything looks fine.

A. As I answer this, I’m listening to a weather report about yet another approaching nor’easter rainstorm. This is a good time of the year to find leaks, due to the snow and the rain. That probably isn’t too comforting to you in your frustration, but your problem can be solved.

I looked at your photos and saw what to me could only be described as a mess. Brown stains are the result of the dark tar leaching like a soup and streaming or trickling in. You often see dark stains like this on ceiling tiles in commercial buildings. Tar isn’t the answer unless the roof is a built-up installation, composed of multiple layers of hot, applied tar and asphalt papers made for this purpose. It looks more like a layer of asphalt roof membrane that was coated (and that’s a polite way of putting it) with roofing cement.

That cold-applied gooey tar substance will last only a few seasons before it splits. Tar can’t permeate the roof materials unless the two substances are compatibly heated. If the molecular structure, the distance between molecules, isn’t spread apart, the tar won’t really take hold.

I also question whether the roof edges that join the house were “flashed” with membrane or metal, and whether the roof edges have been sealed and doubled back. I once found a leak that had already cost an owner about $20,000 to try to solve just by looking above the area to the tops of windows on the upper floor. They had excavated the foundation and sealed roof membranes, etc., only to discover that two pieces of metal covering the top of the windows above did the trick for less than $100. In your case, I would start above, examine the roof and wall openings, and work down the face of the house to each junction of dissimilar materials.

Covering everything in tar is a mistake. To really solve your problem may now involve stripping the roof to examine the wood structure for staining, if all else fails, but try looking from the inside first, since the ceiling is down. Good luck!

© 2019 Monte Leeper. Readers are encouraged to send questions to yourhousedr@aol.com, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.