- Question: We need to replace the steel lintel angles above windows. The exterior walls are solid clay masonry with a total thickness of approximately 12 inches. There is no cavity space in the wall system and the exterior wythe is tied to the interior wythes with brick headers. In the original building, there was no flashing above the steel lintel angles. Since this is not a cavity wall, is flashing required above the heads of the windows?
Answer: I recommend placing flashings above the heads of the windows. Although there is not a free draining cavity space within this masonry wall, some water that penetrates the masonry will travel downward. In portions of the wall that do not contain openings, this water will stay in the masonry and be absorbed by the masonry materials of the wall system until it evaporates. At windows, however, the masonry wall is interrupted. Water travelling down within the wall will flow into the interior or onto the head of the window. This can cause interior leakage or damage at the head of the window. Installing a flashing system that, at a minimum, extends through the exterior wythe will help prevent this from happening.
A second reason for installing flashings above the steel lintel angles is to protect the angles from water. In most cases, where angles are replaced on older buildings, this is required because of excessive corrosion. Water that accumulates on the surface of the angles will promote corrosion. Flashing will help prevent water from reaching the surface of the angle, thereby reducing the rate of corrosion. As further protection, I recommend that the angles be hot dipped galvanized. Although installing a flashing will prevent water from reaching the angles, some water will still reach the angle as a result of condensation. If the interior building temperature is cool during the summer months, warm moist air within the wall system will condense on steel lintels that are cold because they are attached or in contact with the interior wall construction.