We are making several isolated flashing repairs in a brick veneer wall that has no horizontal expansion joints below shelf angles. The budget doesn't allow us to cut new joints at all locations right now. Should we install expansion joints at the locations of our repairs? Would this cause more harm than good?
Don't install partial horizontal expansion joints. Installing expansion joints in only some locations along a horizontal line in a veneer wall can increase compressive stresses in unrepaired areas. The increase in compressive stresses can lead to spalling, cracking, and other problems with the existing masonry. Assuming there is no distress related to the lack of horizontal expansion joints, I recommend installing the masonry tight to the bottom of the angle during your repairs. If there is distress, cut new expansion joints beneath the entire length of the angle. Before cutting any horizontal expansion joints, you should verify the connection of the shelf angle to the structure. Vertical moisture expansion and thermal expansion of the masonry may have disrupted this connection in many locations.