Beekeeper, the fireplace is flush with the surrounding Duroc, so the stone projects out past the fireplace. This particular stone averages about 1" to 1-1/4" in thickness. Each of these stone companies have a spec. sheet that gives the approximate dimensions of their products. I had brick leftover from the outside walls so I just cut 2" inches off the brick to make the border around the fp unit. The bricks are adhered directly to the Duroc with mortar and screws. So the brick border stands out a little past the stones. I dug out some construction photos that may help.beekeeper said:Thanks for the info - we've been browsing around on the OC site and liked some of the ledgerock - I think that's definitely what we'll go with then. One thing I've not really been able to figure out - how much thickness does the stone add, not including the durock?And did you let it extend a little beyond the fireplace, or did you design it so the rock is exactly flush? Thanks!!