A properly built brick wall can take a lot of leakage around the brick, without letting any water into the house. The air space behind the brick is designed to let water run down the inside face of the brick. With building paper against the wall on the other side of the air space, any water that manages to get across to the wall will also flow to the bottom. Weep holes-missing mortar in the vertical joint of about every fifth brick on the bottom row-allow the water to then flow outdoors. These holes also allow air to dry out the cavity. This system is based on the "rain screen wall" principle (see page 155). Properly built, there is no need for any sealing or waterproofing of the brick. Make sure that you do not seal the weep holes. Check that the flashings around the windows are properly caulked and that there are no significant cracks in the mortar.