Hi,

I have a 150 year old balloon-framed house built into a hillside overlooking a harbor off of Long Island Sound. Climate zone 4a (North shore of Long Island, NY). The dining room and kitchen are in the “basement,” which is, on two sides, partially above grade and partially below grade. One of these sides is an inaccessible void under a front porch, and the other has a paved pathway with steps. This side also has an interior staircase. The basement currently has a wood-framed wall inside with fiberglass batts, which was installed about 35 years ago.

Underneath is partially inaccessible crawl-space, with the original joists sitting on the brick ledge over exposed soil, and partially a sub-basement. We have had substantial moisture issues leading to mold growth in the area under the porch (where there is currently a bathroom, which we demolished to remediate the mold.) We are going to completely gut this level, and apply proper air and moisture sealing.

I have read the very-helpful article on here regarding insulating old brick walls, but still have a few questions. We really need the wall the interior staircase is on to be exposed brick, with at most glued drywall or veneer plaster, as removing the framed interior wall would allow us to widen the staircase from 25″ to 30.” I came across this detail: https://hammerandhand.com/best-practices/manual/7-basements/7-4-basement-retrofit/  however i’m unsure if this detail would be safe against the above-grade portions of a structural brick wall. I’m also slightly concerned about having a portion of uninsulated wall – it might be possible to apply EIFS to that wall, but that would only take care of the above-grade portion.

For the walls without the need to omit the interior framed wall, the intent is to apply 1 inch of XPS between the studs and the wall, and install mineral wool in the cavity. The sub-floor would be remediated with gravel, 2″ XPS and 6mil poly – a scratch coat of concrete is not currently planned.

Thanks!