Liquid Flashing The Threshold of a Large Patio Doorway – GreenBuildingAdvisor

Hi GBA Folks,

Bit of a last minute preparation question. I have very large mulled Loewen patio door units that will be installed on a concrete slab out to a covered patio. The transition is all on the same level. The patio concrete hasn’t been poured yet. I have 4″ of XPS foam continuously under the slab, however the foam tapers as it meets the stem wall of the house. At doorway threshold opening you can see where the slab edge ends and meets the foam/vapor barrier taped to the stem wall. (Theres a 1/4 gap where the slab shruk away from the vapor barrier.

Can I safely prepare this threshold by slathering Zip Liquid Flashing over and into the area in question? Essentially coating the entire threshold area of the concrete and up the sides of the RO doorway 3-4″ inches. I have some Prosoco Joint and Seam filler as well as Zip Liquid Flash.

Bit of a mad dash to prepare before the doorways thresholds before door/window installers start on Monday.

Thanks You!