My house, about 40 years old, has a partial brick exterior. The bricks are in great shape, so far. But I think I am beginning to see the first signs of deterioration, especially on the sills outside the windows. I am thinking of putting a concrete sealer on the bricks, which it is claimed is also suitable for bricks. Is this a good idea?
What kind of sealer is best? Could a sealer cause more harm than good by sealing in moisture? How to prepare the surface of the bricks? Your views would be highly appreciated.
Brick exteriors work very well as siding, even in our extreme climate. The answer to your question will depend on the type of brick used on your home. I will offer different opinions, which will vary with the composition of the bricks on your home.
Before answering your question, directly, we should talk about the function of the brick on your home. Because of the age of your home, I am assuming that the exterior walls are wood frame construction. In this situation, the partial brick exterior was a brick veneer, which serves as siding material for your home. This brick veneer has no structural properties and is simply the final exterior component of the building envelope. This is different than very old homes that may have solid brick exterior walls, which are structural as well as providing the exterior protection from the elements.
Brick veneer is typically installed outside the wood or plywood sheathing on the exterior of the wall studs on a home. Behind this brick façade is building paper and a small void space. These two components act to prevent wind & moisture intrusion into the house wall and allow drainage for moisture, which may collect behind the brick veneer. This small gap is very important, as many types of brick are porous and can allow moisture to wick through to the back side of the veneer. This type of construction can normally be identified by small gaps in the mortar or “weep holes” in the bottom row of brick. These weep holes act as small drains to allow the moisture collected in the void to drain to the exterior and not become trapped in the cavity, causing damage.
There are many type of bricks on the market, but for our discussion I will simplify them into two general types, clay or cement-based composition. Clay bricks were commonly used for construction of older homes with solid brick structural exterior walls. These are often identified by their characteristic red colour, but many other colours and shades do exist. These were not as commonly used in homes your age, but may be present as brick veneer. Also, reclaimed brick is now very commonly used for brick veneer and can give a home a desirable weathered look. If this is the material on the outside of your house, then sealing it with a concrete sealer may be useless or possibly detrimental. Clay brick is inherently porous and should be left unfinished to “breathe” after wetting from rain or snow. Sealing the surface may not completely prevent moisture getting behind the veneer, but may prevent normal drying and evaporation of moisture from the brick, itself. This can commonly be seen when older clay brick is painted, with the paint peeling off not long after application. The sealer may have the same result and may not be effective as a waterproofing.
In homes of your age and newer, often Portland Cement based bricks were used as siding. It may be possible to paint or seal these bricks with concrete sealer to prevent spalling or surface deterioration. These should be fairly easily distinguished from clay bricks by the rougher surface texture. If these components are deteriorating on the surface, patching the damaged areas with cement based patching compounds before sealing may help prevent further deterioration.
The area below your windows on the exterior may be the worst location for deterioration, due to ice and snow build-up in the winter. Clearing these areas of ice and snow may be the simplest and most effective method to prevent further damage to the bricks, regardless of composition. If the deterioration is only minimal, as you suggest, this simple maintenance item be all that is required.
If you do indeed have older clay brick veneer, which is moisture damaged and may not be practical for sealing, replacement may be the only option. If you have a few extra bricks in a garage or basement, they may solve your problem. A good mason should be able to remove a few individual bad bricks and mortar in replacements. The colour may not match perfectly at first, but if the same brick is used, it will weather and match after several seasons.
As far as a recommendation for the best type of sealer, your guess is as good as mine. Most bricks are designed to be installed with minimal maintenance for many years without any finish, whatsoever. That is the main property that makes them excellent for veneer siding. Care should be taken when applying any sealer or finish to prevent the necessity for regular repeat coatings or damage to the brick veneer. Check manufacturer’s instruction very carefully and consult websites or toll free numbers from any manufacturers that claim their sealers are suitable for brick.