Whenever it rains, with winds from the east, I get a leakage through the walls that runs down onto the kitchen ventilation duct then onto the stove. I have had the windows replaced, strip and re-roofed my entire house, and replaced and sealed all the flashings on the roof with no success in stopping or diminishing this leak. The eave is also below the top of the brick/block wall, so I've ruled out blowback under the trough. What would you suggest?
Brick wall leaks are usaully caused because a lack of weep holes, or a lack of flashings in a brick veneer wall. Surprisingly, wind-driven rain will pass through masonry walls, mostly at the junctions between the mortar and the bricks, although depending on the brick and the mortar, the rain can also pass right through the body of either one. Often people confuse this with a roof leak or window leak.
Moisture passes through a brick wall if there is a driving force. This force is the wind. If the pressure of the wind is much greater on the outside face of the brick than on the inside, moisture will be driven through. The vented rain screen principle reduces the pressure difference across the masonry. The veneer is built 1 inch away from the wood frame wall. Holes in the bottom of the brick veneer allow the wind to drive into the cavity behind the brick. As the wind pushes in, it pressurizes this cavity. As the cavity behind the brick becomes pressurized, it decreases the pressure differential across the brick. This means that less water drives through the brick. Now that we've reduced the amount of water that gets through the brick, the next step is to get rid of the water. The majority of the water that penetrates the brick will run down the back face of the brick. Any water that finds its way to the frame wall (along a brick tie or a piece of mortar that bridges the 1 inch gap, for example) will run down the outside of the sheathing paper. www.robertevansjrcontractinginc.com
At the bottom of the wall cavity, a metal or plastic flashing collects the water and carries it outside through the weep holes. The flashing should extend about 1/4 inch out beyond the face of the wall, run under the brick, and up the face of the stud wall about 6 inches. The sheathing paper overlaps the flashing so any water running down the sheathing paper will be directed over the flashing, rather than behind it. The holes in the brick veneer that allow the wind to enter and pressurize the wall also allow water to flow out. These weep holes are really air pressurization holes and water drainage holes. Some masonry veneer walls have rope wicks instead of open weep holes to allow water to drain out of wall cavities. Wind cannot push through these wicks and pressurize the wall cavity. If you see rope wicks, the wall cannot act as a vented rain screen. It may or may not perform adequately. Weep holes should be provided at the bottom of the wall, typically about every fourth mortar joint, and should also be provided anywhere water may collect in the wall. For example, where a wall has a door or window opening, flashings and weep holes should be provided above to allow water to escape.