I have a home in the northeast that was built around 1950. I am attempting to fix a crack on what I thought was a plaster wall. As I pealed back a previous repair to the crack I noticed that the material seems to be particle board with plaster on top. Behind the wall is a 4 inch space then cinder block. I had purchased plaster washers to shore up the crack and was planning on using a three foot roll of fibermesh and an application of joint compound to recover the wall. The plaster washers do not grip the material. I can get them to grip on two studs that I managed to find.
What material is the wall made from? And will the washers still work for whatever this material is?