I have 4x8 and 4x9 stucco on Masonite siding on my spanish 2 story. The original 33 years ago went bad and Masonite provided replacement siding but the grooves that interlock together on sides are different as the thickness is different. I am trying not to replace sheets as I will have to do the whole side of the house to fix one sheet as a new sheet is not compatible with older sheet. On the lower corners and bottom edge water has shrunk the fiberboard. I am wondering has anyone found a way to repair the water soaked corners maybe by hardening the material and some plaster repair. The area's are often 3 inches wide and 3 inches high on a full sheet. Maybe KILZ over the top of the repair would prevent water from being absorbed after the repair, if anyone has a suggestion in the first place?
We used to call this stuff Stuccado Plywood, but it is stucco finish over hardboard. If I had the cash I would replace with concrete board!