Replies

1. 
   Scooter1 | Sep 24, 2004 01:26am | #1

   No. Your substrate has to be stronger. The thinset is different. The trowel size is different. And I wouldn't have Natural Slate in my shower for the world.

   Natural Slate is best deserved for the blackboards.

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934

1. 
   EricPaulson | Sep 24, 2004 02:34am | #2

   Ok Boris.........I'm intrigued.

   I've done a few slate floors (12x12) using same as tile methods, thinset over plywood.

   Other than the fact that you don't like it, can you tell us what is so special about the method or materials needed for a proper installation.

   EricEvery once in a while, something goes right!

1. 
   Scooter1 | Sep 24, 2004 03:08am | #3

   Tile has to have a ridgidness of L360; Natural Stone requires L720.

   I am disappointed that you would install tile over plywood. The TCA Guidelines require tile over approved substrates like mud beds, backerboards, and in some cases membranes over plywood. I would urge you to seek some additional training in this regard.

   Natural stone generally requires a medium bed thinset, not the regular thinset. Liippage is an issue with this stuff, and one needs the medium bed to level the stone.

   Natural stone generally requires a larger format trowel, not the usual quarter inch job.

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934

1. 
   EricPaulson | Sep 24, 2004 03:59am | #4

   >>I am disappointed that you would install tile over plywood.

   Based on TCA guidelines I can understand why you would say this. And not to get in a pissing contest, but why is tiling and setting stone over plywood so widely accepted, and why do manufacturers of thinset products specify for use over plywood?

   I have been glueing 3/4 cdx or 3/4 ul over subfloors and never experienced problems. I use yelow glue, liberally applied, and screw the living bejeepers out of the ply, to the joists and two rows in between for a total of around 150 screws per sheet. Makes for a very stiff membrane in my opinion.

   I have NEVER had problems; EVER. I remember using the 2 part epoxy system over ply, till the modified thinsets became the accepted standard.

   I understand that in wet or damp situations, ply is not the best choice. Short of re-engineering an existing structure though, I will put plwood under tile any day rather than non structural cbu or add cbu on top of 2 layers of ply and create elevation differences.

   I understand the lippage, not as big of a problem with gauged slate but is still. That's what makes it fun for me. You know, now that I think about it, both small slate jobs were over a mud base, one was a hearth, and the other was a powder room with a way out of level subfloor.

   Thanks for your input Boris, and I'm not even the original Poster!

   Eric

   Every once in a while, something goes right!

   Edited 9/23/2004 9:13 pm ET by firebird

1. 
   Scooter1 | Sep 24, 2004 10:25pm | #5

   Eric:

   Some manufacturers of thinset mortar allow the use of their mortars over plywood, in direction violation (contradiction) of TCA Standards. These same manufacturers also say that using mastic is OK in showers. I don't get it, it makes no sense, it is wrong, and I guess if you violate the industry standards in installation of tile, then you do so at your own risk. I think all of us can agree that the better way is to install the product over a CBU or membrane. That being said, other than the expense for an admitted better job, I would not see any downside in doing so.

   I decline to get in a pissing contest, because you are right--Custom Building Products does in fact state that you can use their mortars over plywood, and they also encourage the use of mastic in showers, in direct violation of TCA. I think they're nuts, and think your installation technique sucks, but hey, its your license and insurance, not mine. So you go guy.

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934

2. 
   JeffBuck | Sep 24, 2004 11:05pm | #6

   aside from the fact I like slate ...

   I agree with what you said.

   I'd only add that even a modified thinset .... mixed with water ... just doesn't have enough grab and stick to work in the long run with slate.

   Years ago when the tile setter knew how to mix and add lime ... maybe ...

   but since I don't ... I insist on using an additive for stone installs ...

   kerabond with keraply and keralastic by Mapei have worked well on a coupla larger jobs ...

   just plan ahead and use a coupla cheap trowels that'll be disposable afterwards ...

   JeffBuck Construction, llc   Pittsburgh,PA

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