Hi Everyone, I own a window and door supply & install business, sourcing European aluminum systems for residential builds. We do a decent amount of retrofit work – For retrofits, we always recommend some cladding removal around the perimeter of the rough openings for proper WRB tie in (stick & peel tape tie ins to the existing house wrap) – along with assessment of existing header flashings for their quality & appropriate placement. One challenge we come across every now and then is shoddy or old homes that have wall makeups and facade conditions that are either worn down or completely not up to date with code requirements or simply subpar for water shedding or moisture diffusion.

In this specific case, we have a few doors going into a siding wall type. The wall makeup inside to out seems to be as follows:

– Drywall / 6mil poly
– 2×4/2×6 stud framing (depending on the opening location)
– tongue and groove sheathing
– Siding right over sheathing, with no/minimal airgap

I am really looking for some insights as to best methods for installation given the lack of appropriate building envelope variables – My gut tells me to use a liquid flashing on the perimeter given the wall framing /substrate is not really smooth. Install behind an assumed line of drainage (possibly by following the line of installation of the existing windows) and to seal with foam, back caulking. However, I am concerned that I don’t have control over the facade drainage variables, and worry that this could put the openings at risk for water and air leakage. Then again, these variables are outside of my scope of work and responsibility.