I posted previously about a cleanout beneath my fireplace in my basement and my desire to xps over it...and the surrounding poured concrte wall. Anyway, that one particular area is not poured concrete, its cinder block. I had been gluing the xps and affixing it with fur strips then framing in front of it. My Blue concrete screws however are no grabbing the concrete block. I think perhaps the hammer drill might be crumbling a hole...not sure. All I know is, though glued, its not tight. The studs will likely help but I wan the foam nice and tight. What can I use thru my fur strip into the cinder block?