Repair or replace sheathing behind brick veneer?
I wanted to get some advice on what to do with existing sheathing material that is currently installed behind brick veneer in a 1980’s home I’m currently renovating. It’s located in Houston, is 2×4 wood frame construction on concrete slab foundation, and the other parts of the house have T1-11 and vinyl siding (which will all be eventually replaced), but my questions concern what to do behind the brick for now. Much of the interior has been gutted down to the studs due to issues with mold and pests. In the parts of the house with brick as the exterior, there is a layer of 1/8″ sheet material attached to the exterior of the studs, a drainage cavity, and then the brick. There’s some kind of black flashing coming up from below, sandwiched between the stud and sheathing. The sheet material looks like a cross between mineral fiberboard and masonite; it has a paper-like backing that is metallic in color, and after removing the drywall and insulation, a few holes have been uncovered, ranging somewhere between the size of a quarter and that of a grapefruit. These look like they were caused by punctures, possibly during construction, or mostly by ant infestations, as the holes usually are found with dirt piles nearby or pouring out of the holes. In a few sections, behind what was once a tiled-shower wall, there is a bit of warping of the material. The warping has caused the sheet to pull away slightly from the studs, and there are a few noticeable gaps where the sheet is no longer in direct contact with the wood. There are also one or two areas where the sheets were too short and do not overlap, so that the wood stud is exposed to the exterior. There seem to be remnants of mold on the surface of the sheet, but not the composite – but I also have yet to cut up larger sections to confirm this.
Most of what I’ve across so far about issues with sheathing + brick are flooding related. My moisture issues have been limited to the wet areas of the house, and do not seem to be coming directly from the exterior, as far as I know. I’m wondering if the sheathing is fine to leave in place, to clean it with detergents, spray with isopropyl alcohol and use a HEPA vac on the remaining spores – the same process I’m using on the studs. If that’s a viable option, my question is then how to fix the holes and the gaps that have opened up. In an article by Allison Bailes (“How I Fixed My Leaky Underinsulated Exterior Wall”), he uses a combination of XPS and spray foam, but I was wondering how that might translate to my specific area and situation. For the exterior walls of the house, I have been planning on using a natural wool insulation, followed by a fiberglass-backed drywall and a lime plaster coating. The shower areas will receive a tadelakt plaster treatment over Kerdi boards/system. The HVAC systems will not be used very frequently, and the priorities are to prevent as much as possible any future mold growth, while still using more people friendly materials.
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