I live in a townhome and have a space underneath my external stairs up to the main entryway that was basically a catchall junk space for the previous owner. I want to turn this into an actual usable space since that’s a premium in my garage. Until now, I’ve mostly used it to store things I don’t need or things I don’t care are subject to wild humidity variations. Our basement is totally above-ground and connected to the garage.
Ideally I’d like to seal this room from at least moisture so I can store something other than weathertight boxes here. I already had the external masonry repaired, but not sure how to tackle the inside. My first inclination was to clean it out and seal all of the surfaces with silane. The doorway leads back into the garage and I keep it open all the time to help reduce the moisture in the room. Is there anything else I can do to help make this room useable? The outside doesn’t really get direct sun because of surrounding trees.