Insert Window Replacement in Brick Veneer

Insert units can be acceptable in some walls, but this assembly and the prior leakage make them risky as proposed. The existing brick sills slope inward, the original frames have no sill pan or end dams, and the prior inserts relied on caulk at the brick mold. Caulk is a maintenance seal, not flashing. Water staining below the sill after wind-driven rain is evidence that water is getting behind the insert or through the old frame and is not being directed to the exterior. An insert leaves the old frame, brick mold, and sill in place, so a proper pan and back dam are difficult to install and the condition of the hidden rough opening is unknown. A full-frame replacement allows removal of the old frame and sill, inspection and repair of sheathing and framing, installation of a sloped sill pan with end dams, integration of flashing with the water-resistive barrier, and air sealing at the interior. If cost rules out full-frame, then the inserts must be treated as a flashed opening: remove the old sill and interior trim as needed, install a pan and end dams, integrate jamb and head flashing, and test. Caulk alone is not acceptable.

Remove the window, storm, brick mold, and enough brick and sill to expose the rough opening and the water-resistive barrier. Inspect and replace decayed sheathing or framing. Establish a positive slope to the exterior and install a self-adhered sill pan with a back dam and end dams that turn up at the jambs and integrate with the WRB in shingle fashion. Install the new window level, plumb, and square, shimmed at the sill and jambs, and fasten per the manufacturer. Air-seal the interior gap with backer rod and low-expansion foam or sealant, and insulate the frame-to-rough-opening gap without blocking drainage. Install jamb flashing over the sill pan and behind the WRB, then a head flashing with end dams and a drip that laps over the window flange and integrates with the WRB. Rebuild the brick veneer with through-wall flashing at the base of the opening, weep holes at 24 inches on center, and a clear 1-inch air space. Exterior sealant should be a secondary detail at the brick mold and shall not be the primary barrier. For an insert, a similar pan and end-dam detail is required, but space is limited.

I would require a field water test of the two previously leaking windows and one control window after the repair, performed by a qualified technician using a recognized field test method, with the interior observed for at least 15 minutes during and after the test. The test should direct water at the window perimeter, sill, and head, not just the glass. I would also require an infrared scan of the interior wall below the sill at a temperature difference of at least 15 degrees Fahrenheit, and moisture readings of the drywall and framing before and after the test. Visual verification should confirm that the sill pan slopes out, end dams are present, the head flashing has end dams and a drip, the WRB laps are correct, and the air seal is continuous without blocking the drainage path. The owner should receive photographs of the flashing before the brick is reinstalled. Acceptance should be written: no water at the interior, no increase in moisture content, and no staining or soft drywall. If the windows cannot be tested before close-in, a mock-up of the same detail should be tested first.