Hello. I had the fireplace removed in my house but the back wall bricks are in bad condition. The surface is crumbly around the area behind the opening, but seem to be ok higher up. Although the quick job would be just to cover it I want to ensure the structure is still strong it may make sense to replace these bricks as suggested by my plasterer.
Should I be concerned about this? I’ve lost about 2cm depth of the brick so far from it crumbling.