Moisture is the enemy of exterior brick walls
Q. I am planning to build a new house using brick veneer walls. I like the look of old, recycled bricks. What precautions should I take to make sure the brick wall holds up and does not crack?
A. Most brick houses built today are actually brick veneer and not solid brick as they used to be constructed. With brick veneer construction, a lumber-framed wall supports the entire house. Instead of covering the walls with siding, a brick wall is built against the framed wall. Metal ties from the framing secure the brick veneer to it.
Brick appears to be a very hard durable material and it is, but a brick wall is not maintenance-free. Assuming the brick is laid properly and the proper type of mortar is used, the primary enemy of a brick wall is moisture.
This is true for all climates, but especially in cold climates. Moisture can degrade the mortar over time and this weakens the entire wall and creates uneven loading on individual bricks. In cold climates, brick and mortar that get saturated go through repeated freeze/thaw cycles. This can destroy even the best brick wall.
Using old recycled brick can be attractive, but is has its risks for a brick veneer house wall. If the recycled bricks are from an older solid masonry wall house, not all of the bricks are equally strong and moisture-resistant. Less expensive, weaker bricks were used on the interior layers because they did not have to be exposed to the harsh outdoor weather.
Bricks are rated by the manufacturers into grades depending upon the weather conditions to which they will be exposed. Severe weathering (SW) bricks are the most dense, hardest and absorb the least amount of moisture. Moderate weathering (MW) bricks are the next grade lower, but are still used in most colder climates.
Negligible weathering (NW) bricks are the softest and should be used in only the mildest climates where there is no chance of freezing. These bricks are less expensive and are also ideal for interior decorative brick walls. Even in mild climates, select SW bricks where they come in contact with the ground.
The mortar is generally the weak link in a brick wall. Mortar is formulated (lime, cement, and sand) to be softer and somewhat elastic. This allows it absorb slight movement within the brick wall. A harder mortar mix would break and lose its adhesion to the brick. When this happens, wind-driven rain can be forced in through the cracks.
The best maintenance for a brick wall is actually not to the bricks at all. It involves keeping dampness and water away from the bricks. Overflowing gutters and improper drainage and grading around the house are common causes of brick wall failures. Sealing the wall with liquid sealers can help.
A settling foundation can also cause brick wall failures, especially the diagonal cracks. Be sure to have the soil tested and the proper foundation design for the soil type.
If your brick wall does get a narrow diagonal crack, first seal it with matching caulk. Give it a year more to see if the crack widens. If not, remove the caulk and fill it in with mortar. If the crack widens, a mason will have to repair it.
• Ms. Builder's column appears in Homes Plus. Send questions to Ms. Builder, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit dulley.com/msbuilder.
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