# Grout for marble tile



## bert0168 (Jan 28, 2008)

I am going to install some polished marble tile in a small bathroom floor.

I am wondering if I can use the same sanded grout I would normally use for ceramic. I have seen mention here of epoxy and "resin" type grout but the stuff I would prefer to use is colored, just add water powder, like Polyblend.

Am I OK to use this stuff?


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## kevjob (Aug 14, 2006)

marble should be set with 1/16th or under so use non sanded so you don't scratch surface


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## Tileworks (Jul 9, 2005)

bert0168 said:


> I am going to install some polished marble tile in a small bathroom floor... I am wondering if I can use the same sanded grout I would normally use for ceramic.


No, those sand granules will scratch and take the shine right out of your marble. Marble, set properly, should be almost butting one another, but not quite. You can use a non-sanded grout of the same color, even from Polyblend.

- Bob


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## R&D Tile (Apr 5, 2005)

What do you have for a subfloor?, if wood, I would first see if it will support stone.


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## bert0168 (Jan 28, 2008)

Thanks about the sanded grout, I probably would have not thought of that. I was going to go 3/16 on the joints but now will go 1/16.

I have 3/4 subfloor with 1/2 Durock cement board so I think I am OK there

One more, I assume that since the marble is so soft, I will be wet sawing all of it.

Is it possible to score and break it?


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## Tileworks (Jul 9, 2005)

bert0168 said:


> Thanks about the sanded grout, I probably would have not thought of that. I was going to go 3/16 on the joints but now will go 1/16.
> 
> I have 3/4 subfloor with 1/2 Durock cement board so I think I am OK there
> 
> ...


No, you cannot score and break natural stone, only ceramic and porcelain.

Technically, according to the Marble Institute of America, you need to double that plywood. You also want to make sure that your joists are appropriately spaced and spanned. The deflection standards for stone are double that of ceramic.

I've seen marble installed short of the requirements and live, but I have a moral obligation to inform you of the facts 

- Bob


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## R&D Tile (Apr 5, 2005)

Agreed, so far that floor isn't up to spec for stone and I doubt the joists system is either, but we'll wait till you get back with the joist size, spacing and length of unsupported span.


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## kevjob (Aug 14, 2006)

try here for deflection: http://www.johnbridge.com/vbulletin/deflecto.pl Have you set marble before? use medium bed.


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## bert0168 (Jan 28, 2008)

kevjob said:


> try here for deflection: http://www.johnbridge.com/vbulletin/deflecto.pl Have you set marble before? use medium bed.



Thanks for the link. I get a deflection of L/818, over what is needed for marble. It's a small bathroom floor, 5' x 8' with a 12 x 12 tile.

2 x 8
16" o.c.
8' span

No I have not set any marble before, plenty of ceramic. Any more advice before I get to it?


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## kevjob (Aug 14, 2006)

do some searching here http://www.johnbridge.com/vbulletin/index.php?


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## R&D Tile (Apr 5, 2005)

bert0168 said:


> Thanks for the link. I get a deflection of L/818, over what is needed for marble. It's a small bathroom floor, 5' x 8' with a 12 x 12 tile.
> 
> 2 x 8
> 16" o.c.
> ...



Is that the size of the room or the unsupported span of the joists, those joists only run 8' till a support?, if so, you still need two layers of wood.

You want to space them 1/32 to 1/16", the floor needs to be FLAT and you don't ANY lippage.


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## bert0168 (Jan 28, 2008)

No, the span in the room is only 5'. 2nd floor over a beam on one end and near an exterior wall on the other.

I have 1 layer of 3/4" with a layer of 1/2" backer which with taped and mortared seams and nailed and glued to the subfloor. (I use ring shank drywall nails because I hate the rock on screws and can never get them sunk flush)

I know 8' sounds short but it's in a townhouse. Don't ask me why they built it that way.


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## orson (Nov 23, 2007)

1/2" backer doesn't really gain you anything but height on the floor for future reference. It isbasicaly meant for walls where you are spanning studs.


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## kevjob (Aug 14, 2006)

when you say glue, do you mean thinset under cbu?


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## bert0168 (Jan 28, 2008)

orson said:


> 1/2" backer doesn't really gain you anything but height on the floor for future reference. It is basically meant for walls where you are spanning studs.


I wasn't aware of that as I have been using it on floors for a couple of years and no problems.

So other than a mud set, what are options for floor tile. I am not convinced thinset on wood is good as I have removed some tile floors set on plywood where the thinset never stuck


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## R&D Tile (Apr 5, 2005)

Nothing wrong with CBU on a floor, think he meant you can use 1/4" instead of the 1/2".

CBUs get set in a bed of thinset and screwed down.

You also need two layers of wood before the CBU or a membrane if installing stone.


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## MattCoops (Apr 7, 2006)

I'd stick with thinset under the backerboard. It's not meant to be an adhesive, but fill voids.
The screws are your means of "mechanical" fastening. And I'd definitely use screws instead of nails.
I don't think nails and glue meet manufacturers' specifications for installation of any kind of CBU anyway.


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## orson (Nov 23, 2007)

R&D Tile said:


> Nothing wrong with CBU on a floor, think he meant you can use 1/4" instead of the 1/2".
> 
> CBUs get set in a bed of thinset and screwed down.
> 
> You also need two layers of wood before the CBU or a membrane if installing stone.


 
Yikes!! I didn't mean to insinuate you shouldn't use cbu on the floor, just as R&D was saying, use 1/4" instead of 1/2". Sorry for the poor wording.

I actually prefer Ditra over cbu for most floors, especially if you're only minimally meeting the framing and sheathing requirements.


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## Cache (Sep 18, 2007)

I've seen many stone tile jobs done without two layers of ply. Hardie also claims that 3/4" OSB is sufficient under the 1/4" backer for stone applications. Is that not the case?


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## Floordude (Aug 30, 2007)

Hardie want to sell more product. They will tell you what you want to hear, so you buy their crap. 

The wood subfloor needs to be a minimum of 1-1/8" thick, before any CBU or uncoupling membrane. No if's and's or but's!


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## R&D Tile (Apr 5, 2005)

> Is that not the case?


No, it isn't.:no:


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