I am installing new flashing in a composite masonry wall that has brick headers at every sixth course. I am removing only the lower three courses of the outer wythe to the bottom of the first row of headers. Is it necessary to support the masonry wall above or will the headers carry the wall?
Depending on the height of the wall and the conditions of the headers, it may not be necessary. You need to determine the condition of the brick headers and the masonry wall behind. Even if most of the headers are in good shape, there may be areas where the headers have cracked and are not able to support the wall. I recommend taking a cautious approach: either support the walls with 2x4s or leave sections of masonry in place, working in short (4-foot) open sections along the length of the wall.