Hi, we need to waterproof our stucco house. I was thinking about caulking around the vinyl windows with polyurethane sealant (where stucco butts up against vinyl), applying 2 coats of Loxon XP around each window/caulking (6″ perimeter), then painting the entire house with elastomeric breathable paint. Does this sound like a sound approach?
Yes, this will be a good approach. The elastomeric will need a masonry primer, so you could apply a full coat of the Loxon XP then apply the elastomeric over that. Another option is to just use the Loxon XP (2 coats) over the entire house and not bother with the elastomeric coat. This would also be fine.
Good idea to use a polyurethane sealant instead of regular caulking. It will easily outlast and out preform most caulking on the market.