How do I weatherproof a new window I am adding to a home w/ exterior stucco?
You need about 4″ wide of the stucco removed from the rough opening – be careful to try not damage the existing tar paper waterproof barrier. Carefully bend (roll) the stucco lath and tar paper back to get access to the studs. Use a quality ‘flashing’ material to overlay the window flanges and studs. Various flashings materials are available – some are paper rolls loaded with asphalt or similar petroleum-based mineral oil. One of the best is a self-adhesive butyl-rubber with a foil backing that you peel-and-stick. The application is critical. Since water flows from top to bottom, you work from the bottom up: install a horizontal piece on the bottom window flange, and overlap it beyond the vertical studs about 2-4″. Next, apply the two vertical side pieces, overlapping the first (bottom) pc of flashing, and extending above the top of the window. The last pc of flashing is the top horizontal piece, overlapping the sides pcs of flashing. Check you have a good seal on all 4 sides of the wi
