I am using ZIP on my home rebuild. I loosely followed this Steve Baszek how-to for the opening details: https://www.youtube.com/watch?v=MF9i95ElF_k

When the framer cut the sheathing, on some openings he cut it 1/4-1/2″ short so there is a right-angle notch on the exterior corners. I would like to fill the gap with something. I could use liquid flash but it’s like $15 of goop for a 3×3 window, and it seems like overkill for the job. I don’t need to seal the gap, I just need to fill it so the flashing tape doesn’t have to bridge or fill an inside corner.

I tried a web search for “exterior wood filler” and “exterior wood putty” but they seem to be spec’d for smaller defects like nail holes and gouges. Caulk would work as a filler but I’m concerned the tape will not adhere well. Spackle is not designed for outdoor use and wood contraction/expansion with moisture could turn it to powder over time. Great Stuff crack filler could work but the surface will be uneven, and trimming it down would probably damage the edges of the ZIP.

Any suggestions? I’m leaning toward acrylic caulk on the theory that acrylic will bond with acrylic. E.g. DAP Alex Painter’s Caulk – acrylic formula, specified for exterior use, seals as a bonus, and about 1/6 the cost of Liquid Flash.