Posted 7/11/2014 09:35 (#3962451 - in reply to #3960618) Subject: RE: Cement board or maybe asbestos board.
Southern Iowa
I thought about using some type of cement board (cement siding or the cement board for showers you describe) but was told it's not rated for dirt contact and it wouldn't stand the freeze/thaw below grade. I think the siding would have lasted a while but the cement board usually has about 50% styrofoam beads to make it flexible and easy to drill. Don't think it would last very long.