I need to attach 2x4 studs or furring strips to a block chimney that was built in the 70's. it has mortar marks on it done with a trowel, like they would do in the 70's. I am in the process of covering it with various pieces of wood. I will need to add 2x4's, then add 3/8 plywood over the studs or furring strips for a nailer, then attach the wood to the outside of that. I have a 22 Cal. nailer to blast them in but I am concerned that it would break the blocks. best I can tell they are 4x6" blocks mortared in place. I still will use construction adhesive between the 2x4's and the mortar.
This is on the inside of the house not the outside.