Mystery Material Behind Brick Veneer
My wife & I purchased a brick home in southern Virginia west of Martinsville near the NC boarder that was built in 1973. The house is a wood stud wall with a brick veneer over the stud walls. We started to renovate the inside of the home & when we removed the paneling from the wall in the dining room because of a prior water leak to remove the insulation I noticed a black material that looks like a pressed board on the inside of the brick in the stud cavities. In the stud cavity where the water leak was the black material has all detreated & was wondering what I could use to replace it before re-insulating? The insulation is R-7 & I was wondering should I upgrade the insulation to the common R-13?.
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Sounds like fiberboard sheathing. Some versions of it were also meant to be the WRB but that was mostly an aspirational spec (mostly works but if your brick has issues, it won't keep the water out of the wall).
The problem in your case is that it is between the brick and your studs, there is no easy way to replace it without taking the brick off. Your best bet is to treat the cavity as if it was without sheathing. This is assuming you fixed the source of the water leak:
Keep in mind that the fiberboard is structural part of your house since it provides shear resistance to your walls. You might need to add interior bracing to compensate for the damage. Best to consult an engineer.
P.S. You should defiantly bump up your insulation R value while the wall is open. Cheapest energy upgrade you can do.