I have a brick veneer home and mold.  Just a high humidity day (without rain) is enough to make the house smell bad.  What is your opinion of using a masonry sealer on the brick veneer? –Dale, Indiana 

            I once had a similar problem.  Early on, whenever we had a wind-driven rain, rainwater would come through the brick veneer and run down the basement walls.  Thinking as you are, I applied several coatings of Thompson’s Water Seal to the brick veneer on the south side of the house.  The next wind-driven rain the water again came pouring down basement walls.  Perplexed I then took a garden hose and sprayed the brick veneer and just on the other side the water came running down the basement wall.  I learned from that experience that brick veneer mortar is quite porous and that sealant coatings don’t do much good. 

            I eventually had the brick veneer removed.  What I found was rotting two by fours (at the base) and a very dark stained band board and fiberglass insulation that though it can’t grow mold had a moldy smell because of the leaching of mold-contaminated dust in it.  What I also discovered was that there was no liquid barrier (such as Tyvek) and that there were mortar bridges between the brick veneer and the wall.  These bridges carry liquid rain water to the exterior of the inner wall.  Tyvek will cause liquid water to run down to the base where if there are functioning weep holes the water can work its way out of the wall.  Most building codes require a ¾ to 1” clear gap between the brick veneer and the wall. In this part of the country most masons do not remove the excess mortar and mortar bridging within brick veneer walls is common if not the norm.  It is, of course, a violation of many building codes. 

            Typically wind-driven rains in the Midwest strike the south and southwest parts of a building.  This is where water damage to structural timbers and mold infestation occurs (particularly in the lower two feet of the wall). 

            The mold odor you describe will come and go with changes in relative humidity and is more pronounced on a breezy / windy days.  Houses out in the open, unsheltered by trees and other buildings are particularly prone to water intrusion through brick veneer and the mold and odor you describe. 

            The only solution to your problem is to have the brick veneer removed, remove the affected timbers (or treated with a biocidal sealant), apply a liquid water and vapor felt paper to the outer surface of the wall, and then reconstruct the brick veneer to code requirements (one such gap and functioning weep holes). Alternatively, replace the brick with vinyl or some other less troublesome cladding.

 

June 24, 2005