Do This, Not That! A Trifecta of Mass Wall Masonry Repair Errors.
BEC was hired to investigate a historic masonry mass wall structure built circa 1867 for water infiltration. Immediately, we identified a trifecta of problems including inappropriate coating selection, poor workmanship, and non-compliance with local preservation requirements.
The previous building owner’s response to water infiltration was to install a liquid-applied “waterproof” coating that was completely inappropriate for installation over 150-year-old brick masonry. Not to mention, the coating was applied shoddily enough to leave voids at open mortar joints - defeating the purpose of installing a waterproof coating in the first place. Finally, the installed coating did not comply with the local historic preservation district ordinances.
Mass wall construction must be allowed to breathe to allow evaporation of trapped moisture. Our waterproofing technology did not exist 150 years ago so we must treat the symptoms with a sensitivity to the age of the materials. We generally do not recommend the installation of waterproof coatings over historic masonry walls. Moisture trapped within the masonry and vapor drive from the interior reaches the back of the coating and freezes resulting in spalling if you are in a climate susceptible to freeze/thaw cycles.
When such conditions are presented, the inappropriate coating should be removed and the appropriate masonry repairs performed. Consider that abrasive removal of coatings compromises the hard glazing of the brick unit and exposes the soft porous material inside, contributing to further deterioration and spalling. Chemical removal and proper re-pointing are likely your best options to resolve water infiltration at mass wall assemblies.
For further reading, please check out the following resources:
Brick Industry Association Technical Notes #6 Painting Brick Masonry
Brick Industry Association Technical Notes #6A Colorless Coatings for Brick Masonry
National Park Service Preservation Brief #1 Assessing Cleaning and Water-Repellent Treatments for Historic Masonry Buildings
National Park Service Preservation Brief #2 Repointing Mortar Joints