Pool remodel. Can I put a new mortar bed over an existing mortar bed?

Kpiazzisi

New member
Oct 2, 2021
1
Sarasota, Florida
The guy who is redoing my plaster has 30 years of pool building experience. I have a decent amount of tiling experience although have never done pool tile. Everything I have read says, remove old tile, use hydro stop to repair cracks in the mortar or shell, then seal with a waterpoof membrane, finally use a thin set rated for continuous water submersion. If using glass then thin set must be rated for glass and continuous water submersion. So here is the problem. The pool builder wants me to use a thin mortar bed coat so that the end result will be the waterline tile 1/4 -3/8 over the old plaster. That way he can float the new plaster even with the tile. I don't think it's a good idea to put a new mortar bed over an old mortar bed? He is also saying the membrane (liquid membrane) is unnecessary. Doesn't sound right to me? I am thinking lightly grind the old mortar bed smooth, apply a membrane, maybe use a 3/8 trowel instead of 1/4 when applying the new thin-set? If that doesn't push the new tile out far enough for him, then he can bevel grind some of the old plaster off? What do you think?
 

sktn77a

Gold Supporter
May 16, 2010
2,248
Chapel Hill, NC
Unless you have an existing leak, the membrane is unnecessary. However, if you decide to plaster over the old plaster, make sure it's good and strong and well adhered to the gunite. A bond coat on the old plaster should be used (most people would recommend a complete chipout)
 
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