Preservation Tip: Waterproofing Historic Brick
PSA: Waterproofing the outside of your historic brick building doesn't mean an end to your water problems...
If you are experiencing leaks in your old building, you might think adding a layer of waterproof paint on the outside would fix all your problems. After all, preventing water that's outside from getting in makes a lot of sense at first glance, and a waterproof paint WILL help keep rainwater out. But rainwater isn't the only source of moisture in a building!
While it's true that a lot of historic buildings were painted back in the day, they weren't painted with a waterproof paint — the coatings still allowed water vapor to travel through the wall and allowed the building to "breathe." Adding a waterproof coating to historic masonry means that the moisture from the conditioned air INSIDE your building has nowhere to go — it will travel through your wall from the inside out until it gets to the waterproof coating. At that point, it will stop, trapping the moisture inside your wall. As the seasons change, the moisture can condense, freeze, and thaw, causing considerable damage to your brick. Eventually, the outer portion of the brick will begin to turn to dust and the paint will start to flake off. If left untreated, this kind of damage could be irreparable.
It's always crucial to select the right product for the job. Make sure if you're painting an historic brick building that you use a permeable coating specifically intended for masonry.
BY STEPHANIE WAPLES-BRAKEVILLE
PICTURES Waterproof paint that has fallen off of a building, taking part of the historic brick with it.