When I first started mosaicing I read in one of the many tutorials on the net that it is unadvisable to mosaic onto sheetrock. If I wanted to mosaic on the wall, I'd use backerboard - the concrete board used on countertops in kitchens and in bathrooms. When I dismantled my bathroom backsplash counter b/f I mosaiced it, there was a base of the diamond mesh and mortar. IMO you could go either way - use the hardibacker or put the wire mesh on then use mortar for your mosaic. Show us pictures as you work, please.