replying to Josh, Dan wrote:
joshhemming wrote:

I've installed new 1/2" conventional gypsum drywall in the area
between my kitchen countertop and the bottom of the wall cabinets.
I'm looking for some decorative ceramic tile to use as a backsplash
over/behind the sink and extend it around to the area over/behind the
range. What I'd like to know is this:
Once I find the tile I want to use on that wall, is it necessary to
prime and paint the new drywall before applying the tile mastic? I
haven't bothered to tape the joints yet; figure the 4x4 tiles will
cover the joints anyway. Just wondering if the mastic or thinset
mortar will adhere good enough to the bare drywall without any special
prep.



If your tiling a floor you most surely need a backer board which has been
screwed down every 6" and had all of the joints meshed and mudded or the
grout will crack within months or even weeks. The exception being a level
concrete floor. Drywall is perfect for applying wall tile and backsplash.
Type 1 mastic manufactorer Mapei recommends priming as it "dramatically
enhances the cohesion between the tile, adhesive, paper and gypsum board"
and I think the reason for this is because they sell the recommended
primer. The same instructions go on to say "surfaces should be free of
all dust, grease, wax sealer, paint and primer" if you can believe it. I
tape the joints and maybe add a few screws were needed on unpainted
drywall because if you tile over a crack or uneven surface or floating
drywall, your asking for your grout to fall out down the road. if the
wall has been painted with a glossy paint I always rough it up very good
with a drywall rasp to give the wall some "tooth" for the adhesive. The
main reason tile falls off is exhesive moisture/steam in the room or the
installer put to much adhesive on and it dryed out before the tile could
be applied.

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