There is little debate over brick's reputation as a durable, maintenance-free building material. Brick buildings that are hundreds of years old are still in use today. However, many people don't realize that the older brick buildings were not built like today's brick-veneered buildings. Historically, brick was used to create loadbearing walls, which were often four or more wythes of solid brick masonry. These walls prevented moisture penetration to the interior by their sheer mass. The brick masonry in today's veneer wall is just one element of a drainage wall system, which typically consists of a single 4-inch-thick wythe of brickwork, an air space of 1 inch to 2 inches, and a separate wood, steel, or concrete block backup wall. When moisture penetration problems occur, it is usually because the people building the wall didn't understand some of the basic principles of brick veneer construction.

Brick Veneer Is Not Waterproof

A common misconception, even among some masons, is that 4-inch brick veneer will stop all moisture penetration under all weather conditions. It is important to remember that brick is a porous absorptive material, and that water can penetrate a brick veneer wall wherever there is a lack of material: at bond breaks, hairline cracks between brick and mortar, unfilled joints, movement cracks, and even unfilled line-pin holes. There are all sorts of opinions about whether water that penetrates a brick veneer wall is coming through the brick, through the mortar, or through small cracks in the mortar. But it really doesn't matter how you visualize the moisture entering into the wall system. What matters is understanding the simple, inexpensive details and installation practices that can prevent water problems.

The Drainage Wall System

If you are installing brick veneer, you should expect water on the back face of your bricks (see Figure 1).

Figure 1.

Since wind-driven rain may penetrate brick veneer, it is best to assume that the backs of the bricks will be wet. Unless the water can drain to the exterior, moisture can damage framing or interior finishes. It is important to take steps to allow any moisture to drain from the wall, so that it can't enter the interior. The drainage wall concept is fairly simple: Water that penetrates the exterior wythe of brickwork travels down the back face of the brick until it's collected by through-wall flashing and led to the exterior through weepholes (Figure 2).

Figure 2.