When we inspected this tower, the perimeter sealant had failed at every window and door on the building, and the brick-to-brick control joints had gone with it. That's not a leak you chase one window at a time — that's an envelope at the end of its service life. What we did: replaced about 2,900 LF of window, door, and PTAC unit perimeters with Tremco Spectrem 2 silicone, and about 1,100 LF of brick-to-brick control joints with Spectrem 1. Backer rod in every joint to get the depth-to-width ratio right and keep the bead off the back of the joint — a bead bonded on three sides can't stretch and tears the first time the building moves. Trem-Prime Porous on the brick side of every perimeter joint, because silicone doesn't reliably bond to masonry without it. Access was a 60' straight boom lift on the elevations and moveable scaffolding at the front entry. Residents stayed in their apartments the whole time — this is exterior work, and it never required going inside a single unit. The PTAC perimeters are worth calling out. Those sleeves pass straight through the exterior wall, so a failed seal there is a direct path to the inside. They're the detail most often skipped on a partial repair, and one of the most common sources of interior water damage in buildings that use them. If your building has been re-caulked one window at a time for years, the math stops working. The joints that haven't failed yet are the same age as the ones that have. Performance Waterproofing LLC · TN, KY, AL, GA · contact@performancewaterproofingllc.com