I'm about to put some granite tiles down on my bathroom floor but it never
occurred to me to look at the concrete backer boards more closely. I
purchased 1/2" and it didn't look right so I took my tape and measured it
somewhere between 1/4" and 1/2".
I know with wood, a 2x4 is less because it was planed down at the factory to
the smaller finished dimension. But what's the excuse for concrete backer