I need to replace the masonry through-wall flashing in a multistory brick cavity wall with relieving angles at each floor line. On similar projects in the past, I've removed approximately 5-foot-wide sections of masonry, leaving 4-foot piers between those areas. After completing these areas, I've bricked them up, then removed the remaining masonry piers. Although this method has worked reasonably well, I'm looking for ways to support the masonry until after the flashing is installed, so all the masonry in an area can be installed at one time. How can this be done?
I have seen many different methods for supporting the masonry in these situations. If the existing shelf angles will remain, the most common approach is to remove alternating sections of masonry, install the flashing, and then use 2x4s to support the masonry. The 2x4s must be wedged into place to provide adequate support. Remove the remaining areas of masonry and then install new flashing appropriately spliced to the previous flashing. To prevent damage, contractors often use a horizontal wood member at the top of the masonry opening and at the surface of the flashing. The top and bottom horizontal members should be short sections, so they can be removed easily when reinstalling brick. When the shelf angles are removed, the problem is complicated because the masonry cannot be supported off a shelf angle. Instead, the masonry must be supported either by an independent support from the building structure or by the masonry below the area where the shelf angle is to be replaced. The support system must not interfere with the installation of the shelf angle or the flashing. I have seen several methods of supporting the masonry off the existing structure. If the existing structure has concrete spandrel beams, one easy way to support the masonry is to use shear pins. To install these, drill holes at the intersection between vertical and horizontal mortar joints at the top portion of masonry to be removed. The holes extend well into the concrete structure. A structural engineer should size the dowels or shear pins to support the masonry adequately. When cavities are large, contractors sometimes make small openings to install clip angles that, in turn, are bolted to the concrete spandrel beam. Another approach is for a structural engineer to design a bracket attached on the exterior face of the masonry. The brackets are expansion-anchored to the masonry above and below the area of the masonry to be removed. For this approach, the contractor sets the expansion anchors into mortar joints in the existing masonry, making sure to consider the edge distances and loads on the anchors. The vertical portions of these brackets between the attachment points should be located far enough away from the face of the masonry and spaced far enough apart to ease the installation of 10-foot lengths of shelf angles and flashing. The expansion anchors must be either removable or threaded inserts that can remain in the wall and be covered with mortar to hide them after the repair is complete. Use only stainless-steel threaded inserts to avoid corrosion-induced cracking.