Getting a good bond to very slick plaster skimcoat [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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Vigilant1
01-31-2014, 10:57 AM
Thanks to everyone for all the great information here.

I am retiling our 1950's bathroom. The walls are plasterboard with a coat of plaster (approx 3/8") and skimcoat atop that. The previous tiles were put up with mastic, and they held up well except in the shower, where there was water penetration, failure of the plaster, and some wood rot.

I removed everything down to the studs in the shower, put up hardibacker, and I'm ready to Redgard, thinset, and tile. My question is about the rest of the room (approx lower 48" of walls, not in a wet area). Some of the area was painted before the mastic and tiles were put up, and the paint is debonding from the plaster. I've scraped the paint off (the paint was brittle, came off in "chips"). The walls in these areas are very hard, smooth, slightly shiny. What's the best way to get thinset to stick to this? Will a few passes with 80 grit give enough "bite", or do I need to use an angle grinder?

Thanks for any tips.

Mark

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dhagin
01-31-2014, 11:26 PM
First off, you may have bad stuff in the paint or plaster that sanding or grinding with power tools may put into the air. I'd line the floor with plastic and seal it to the wall with duct tape. Then, try hand sanding with a coarse grit after wetting the wall so there's no dust. Wear appropriate PPE and clean everything up well when you're done - including you & your clothes.

As you may have gypsum plaster, I'd recommend a skim coat of Laticrete 254 after sanding. Then set with 254. :)

Vigilant1
02-08-2014, 11:24 AM
Dana,
Thanks for the reply, sorry for the delayed response.
Yep, I'm being careful and using a respirator, good hygeine, etc. I strongly suspect there's lead in that paint.
I roughed up the walls with 80 grit and it's quite a bit less glossy and "slick" than it was, so I'll give it a go.
Now I'm working on the tile layout for the walls: There will have to be compromises, the tiny cuts have to go somewhere . . .

Mark

Bodie Powers
02-08-2014, 12:52 PM
Not knowing what material is on that that bare wall, I'd want to apply a good primer before tiling. Zinsser would be a good choice.

Vigilant1
02-09-2014, 12:44 PM
Bodie,
Regarding the Zinnser primer: Any preferences for the type? I've used BIN before (stinky, but dries fast, holds like glue and forms an acceptable vapor barrier--sometimes that is good). Or, would you go with 1-2-3 or something else?

Thanks,

Mark

dhagin
02-09-2014, 12:51 PM
I'd say skip the paint and use Laticrete 254 as a skim coat over the wall. You can then use the 254 to set the tile if you'd like. :)

Giuseppex
02-09-2014, 06:30 PM
Plasterweld would be my suggestion.

http://www.larsenproducts.com/plaster-weld-2

Lakee911
02-09-2014, 07:18 PM
I'd roughen it up and use plaster or concrete bonding agent and then modified thinset under tile.
.
If you prime it, wash it real good first and then use an oil or shellac primer. Then thinset and tile