Published on May 2nd, 2014 | by Henri


Faces spalling (falling off) from decorative chimney bricks

Q.    Our 1-1/2 story frame house was built in about 1948. We have over the years corrected a number of deficiencies such as water in the cellar and poor attic ventilation, using techniques that you have suggested in your column. Our current problem started about 5 years ago. The chimney is built, or at least faced, with a red decorative brick, standard size with the face scored.

The faces of some of the bricks were spalling (falling off). We had a mason  suggest applying a material like Thompson’s Water-seal, which he did 2 years ago. The problem persists as the water-seal application has not worked. While this is a cosmetic issue and not structural, do you have a solution?

A.    Thompson’s Water Seal  was not the product to use for this purpose. It is paraffin-based and subject to fast degradation from the sun and other weather elements. The sealer to use should have a siloxane-base to allow the bricks to breathe. The mortar joints need to be sound and the chimney cap in good repair, or the brick treatment will not solve the problem. Unfortunately, the spalling can become a structural issue if allowed to progress too far, so it should be repaired.

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