Question: I was just wondering what could be used as a spacer material to attach the cement backer board to the 2x4 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.