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Tile over plaster walls in bath

remodeling 1970's bathroom. Want to tile around tub, walls. Currently has real plaster. What do I need to put over these plaster walls before I tile, cement board or moisture-resistant drywall? Or, do I have to tear the plaster out first? It's in good shape.

Re: Tile over plaster walls in bath

I take it you installed a tub against an existing plaster wall; I did the same in my old (19th century) house. The plumbing wall was new framing, but the other two walls were three-coat plaster on wood lath. Very sound. The tub I used was an Americast with a 1" tall, but very thin flange at the top edge. I shimmed out the wet wall so the flange was buried (would not cause a bulge/flare at the bottom) when I attached 1/2" durock on that wall, to within 1/4" of the tub rim. On the two plaster walls, not wanting to add undue thickness, I applied 1/4" hardi-backer set in thinset. The whole tub surround was then waterproofed with Schluter Kerdi membrane, with the seams lapped 2". If I had it to do over again, I would totally seal the hardi with Plasterweld or Link bonding agent (a PVA_based liquid), so that the thinset stayed workable; hardi really sucks the water from mortar, making the task of bonding the Kerdi really too difficult for a slow DIY- tiler. The tile went on the kerdi just fine, and I know that it is totally waterproof.

Re: Tile over plaster walls in bath

If your walls are dry so you no need put any kind of moisture resistant plaster.Use simple layer of cement put the tiles over it. I have done same in my bathroom.

Basement Remodeling Contractor

Hank Bauer
Re: Tile over plaster walls in bath

Use the backer board as stated above.
Cement and plaster are like a positive and a negitive magnet they will seperate over time due to moisture. Moisture will cause the plaster to swell and push on the plaster it is called Hygrometric Expansion.

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