Question: I was just wondering what could be used as a spacer material to attach the cement backer board to the 2 x 4 studs in the wall? I've heard of ceramic spacers 1" thick but what about metal tubing or even wood products? Thanks. Answer: You can use vertical strips of the cement board itself. I have also used small pieces of copper pipe. Lastly, a company called HeatSafe sells a ceramic spacer kit.