New Window in an Old Opening

The most difficult part of installing a flanged new-construction window in an old opening is ensuring that the window is fully able to resist water infiltration. Builder and worker-training consultant Bill Robinson says that you can avoid water infiltration by keeping in mind the four Ds: deflection, drainage, drying, and durability. Robinson begins a project by removing the old window carefully, making sure that he doesn't cut through the felt or housewrap. Next, he flashes the rough opening to prevent water from getting inside the building cavity. Robinson stresses the importance of using compatible products for the flashing system. Next, it's time to install the window, then flash the window. Finally, the window is cased, and then Robinson caulks and air-seals the window, again using products compatible with the flashing system.

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