Sherlock Holmes with a tool belt: The case of damp brick walls

Q. Our 50-year-old church has had problems with paint adhering to several inside walls for more than 20 years. Painters told us this was caused by moisture on the exterior brick walls. We've taken many steps, including having the brick sprayed with a waterproofing compound. The problem persists. Any suggestions?

- J.A.L.,

Chattanooga, Tenn.

A. "The steps you have already taken on the exterior should eliminate the need for a sealer," says Howard Clark, a licensed construction supervisor in Hopkinton, Mass. He suggests a new investigation for the source of the moisture.

1. Examine the mortar joints on the exterior brick wall. Signs of loose or crumbly mortar, or gaps between the brick and the mortar that you can slip a razor blade into, indicate a need for mortar replacement through a process called tuck pointing. Surface sealants will not help tired mortar and they may inhibit the ability of the new mortar to bond with the brick.

2. If your brick walls extend above the roof to form a parapet, check the roof flashing on the back of this wall for even minor leaks into the wall system.

3. See that all roof penetrations (stacks, vents, flues) in the area of the troublesome wall are well flashed.

4. Inspect the wall penetration at a hose bib or air conditioning condensate drain line. Can you verify that they are not leaking inside the wall?

5. Check the attic area for signs of moisture. Is overhead plumbing or heating equipment causing condensation? Is the attic properly vented so it stays dry?

6. Finally, look for water problems beneath the wall. Are there sewer pipes, roof drains, or water lines that may be leaking and permitting water to wick up?

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