Brick Veneer Leaking Water at Top of Foundation

By Jason Yana

To successfully design and build masonry veneer walls, one must take a systems approach. Your home's wall is an organized assemblage of interdependent parts which work together to form a building envelope. The wall may be made of a combination of clay brick, concrete masonry units, stone, calcium silicate units, etc. The backup wall for the purposes of this article is wood frame construction. A good designer should know the intricacies of each material and what detailing implications those characteristics may require. This document is intended to aide the homeowner in understanding why moisture is finding it's way into the basement.

Moisture Control

All 4" unreinforced masonry veneers are expected to allow some wind driven rain to penetrate, most likely through hairline cracks between brick and mortar. For this reason, an airspace is designed between veneer and backup to allow moisture to drain down the cavity and exit at flashing and weep holes. All of these systems require proper flashing details to perform correctly. Moisture which does penetrate the wall, gradually travels downward. This makes the base the most vulnerable location for moisture accumulation. A continuous flashing must be properly installed above grade. The correct installation method is outlined in Figures 1 & 2. Proper weeping to provide moisture drainage is crucial. Weep holes MUST be used wherever flashing is located. They must be placed directly on the flashing, and spaced no further than 24" on center. Weep holes can be created in several ways. Some of the most common methods are: leaving head joints open, use of removable oiled rods, and installing plastic or metal vents (not tubes), in lieu of mortar in head joint. Cotton sash cords placed 16" O.C. will also serve as an excellent weep. There is no universal method. Different situations will require different methods. The specific type of weep hole is not critical as long as weep holes are properly installed at required locations in the proper spacing. 

If you do indeed have water running down your basement walls, we need to determine if your walls were constructed according to these widely accepted industry standards.

Potential problems we can see without cutting holes in walls:

• Is there flashing installed at the base of your brick veneer? This one is relatively easy to check. Crouch down at the base of the wall where it meets your foundation. Can you see a thin layer of flashing underneath the first course of brick? It is possible, and acceptable, if the builder installed the flashing and then subsequently cut it flush with the wall - can you see evidence of that?  If you answered no to both questions, your wall may not have any flashing installed at all.  The International Residential Code requires that flashing be installed - your house was not built to code! Go get em!
• Are there properly constructed and spaced weepholes in your brick wall? The weep holes are an avenue of exit for any moisture collected by the base flashing. If you did not find any flashing at all in step one, weep holes will do you no good. The weep holes can be a simple opening in the vertical mortar joints, some sort of weep vent, or a cotton sash cord hanging out of the mortar joint.  They should be spaced no more than 2 feet apart and should continue across the entire wall. Weep holes only do their job if they are located directly above the flashing - not an inch above, not a foot above - directly above!
• The exterior face of the poured concrete or concrete block foundation, which the brick veneer  sits on, should be in the same plane as the finished brick's wall plane. The reason for this is to prevent water from traveling horizontally into the building on the projecting concrete ledge.   [If the concrete wall is that far out of line, the flashing should be set in mastic to prevent water from entering under the flashing. If concrete is out of location, brick can overhang the foun dation by 1/3 bed depth (with 2/3 bearing on foundation) before a shelf angle is needed.
• The finished grade must be below the weep holes ( preferable 2" to 3" below the flashing line). If brick goes below the flashing, fill the space between the brick and the foundation with grout or mortar.

Problems we can only see after removing a section of brick above the foundation - I suggest hiring a Masonry Consultant to Determine the cause of your problem:

• Make sure the flashing is placed behind the building paper or house wrap. (Not in front of the building paper, or water will run between and appear at the wooden sill plate)
• A brick veneer wall is a drainage-type wall system. In a drainage wall, some water will penetrate the exterior wythe of masonry. The water then flows down the inside face of the masonry, is collected by properly installed flashing, and exits the wall through weep holes. This drainage space is critical, critical, critical! There needs to be one inch of air between the brick and the structure behind it. This space can easily become filled with mortar droppings created during construction. If the entire space is clogged with mortar, water will have a very hard time finding its way down to the flashing and will most likely find the wood sheathing first, run downward compromising the flashing and ultimately end up in your basement.
• Flashing comes in a roll, usually, and is not of infinite length. Therefore, occasions commonly arise where the flashing needs to be lapped over itself. When this happens, care should be taken to overlap the joint a good 8 inches and seal the lap with mastic, otherwise water can just find its way laterally across the lap.
• Flashing around corners is a challenge that only an experienced mason can pull off correctly. For this reason, several manufacturers make prefabricated corners which solve this problem.