# Minimum subfloor for marble tile?



## Munanbak (Jan 19, 2011)

Hi tile guys. I am still sorta green when it comes to tiling with marble, and was hoping someone could point me in the right direction.

I will be Tiling a kitchen, hallway, and connected bathroom with a 12x12 marble tile. Existing there now is 3/4 T&G Fir over 2 x 8 from 1920, spanning about 9 ft, actually 14" spacing. There are also crushed nails on the surface (pounded down, imbedded in the wood, umm.... oops).

The adjacent floor, is 3/8 T&G hardwood right on the subloor.

Originally I thought, 

1. Thinset with 1/8" V notch (to take up any proud nails) 
2. Install 3/8" ply
3. Thinset 1/4" x 3/8" trowel
4. Install 1/4'' wonderboard.
5. White thinset 1'4" x 3/8" 
6. Lay marble tile, 1/16" spacing, seal it, non sanded, yada yada yada...

I have a concern with the threshold height. The Kitchen is sort of like a hallway to 2 bedrooms, the bathroom, and the stair landing. I figured I would be about 1 whole inch higher than the the hardwood. That one hell of a transition to be walking through everyday!! The Home Owner seems to be okay with this. But I would really like to have a better solution.

Would Shluter system be applicable here?

Basically my question is, in this situation, what is the minimum subfloor I can lay to achieve a solid surface for laying 12x12 marble tile?

Thanks in advance.


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## angus242 (Oct 20, 2007)

Your joists are under the minimum deflection allowed. EDIT: _barely_ but they are.

For stone, I'd use nothing less than 3/4 T&G with 1/2" EGP. For an underlayment you can use NobleSeal TS which is only .03" thick.

Remember your installation is MOST important; not adjacent floor height.

Consider sistering some of those joists.


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## Munanbak (Jan 19, 2011)

Thanks Angus. NobleSeal seems like a good fit here.

I guess what I was thinking is that the 'step' up to the kitchen would be inconvenient. 

Maybe I'm after a suitable threshold to fit the bill. As for now, I'm considering standard marble threshold, and tacking a cove or quarter in front of it (to ease the transition, and 'hide' the layers).

I'll consider beefing up the joists around the tub.

Really great forum here.


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## jarvis design (May 6, 2008)

Just a thought...if your tile is transitioning to hardwood, you could fabricate a wider "sloped" transition out of the same type of wood. I have had to do this a number of times when dealing with thin oak flooring and a tile floor that needed beefed up


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## Munanbak (Jan 19, 2011)

Yes Jarvis, You're absolutely right. I am going to fabricate a transition strip out of solid oak. The floor finisher is coming in after, so they can hit it with the floor finish.


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## Bastien1337 (Dec 20, 2010)

angus242 said:


> Your joists are under the minimum deflection allowed. EDIT: _barely_ but they are.
> 
> For stone, I'd use nothing less than 3/4 T&G with 1/2" *EGP.* For an underlayment you can use NobleSeal TS which is only .03" thick.
> 
> ...


what this mean angus?


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## kevjob (Aug 14, 2006)

Here is a marble threshold that matches window sill and shower niche.

E.G.P.= Exterior Glue(thanks angus) Plywood


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## Munanbak (Jan 19, 2011)

Bastien1337 said:


> what this mean angus?


I'm assuming Exterior Grade Plywood.


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## Groutface (Jan 20, 2011)

angus242 said:


> Your joists are under the minimum deflection allowed. EDIT: barely but they are.
> 
> For stone, I'd use nothing less than 3/4 T&G with 1/2" EGP. For an underlayment you can use NobleSeal TS which is only .03" thick.
> 
> ...


Angus, noble seal a membrane?


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## Groutface (Jan 20, 2011)

Groutface said:


> Angus, noble seal a membrane?


Nevermind I looked it up....cool!


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## angus242 (Oct 20, 2007)

Groutface said:


> Angus, noble seal a membrane?


You got it. NobleSeal TS is a waterproof, crack isolation membrane that also has excellent uncoupling properties. It can be installed _with_ modified thinset and tile can be installed over it with modified too. :thumbsup:


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## angus242 (Oct 20, 2007)

Bastien1337 said:


> what this mean angus?





kevjob said:


> E.G.P.= Exterior Grade Plywood





Munanbak said:


> I'm assuming Exterior Grade Plywood.


:thumbup:

*E*xterior *G*lue *P*lywood!

I know the carpenters yell at me when I use that initialism. They prefer BCX ply.  But the TCNA handbook refers to EGP so that's what I use so as to not confuse the _tile_ folks that might be reading.


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## Leo G (May 12, 2005)

What the heck is BCX ply. I've seen CDX and ACX, but never BCX.


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## angus242 (Oct 20, 2007)

Leo G said:


> What the heck is BCX ply. I've seen CDX and ACX, but never BCX.


I'm no woodpecker but BCX is one side semi-sanded, exterior glued?

http://www.sdslumber.com/sds_plywoodBCX.htm

Menards sells it.


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## Groutface (Jan 20, 2011)

angus242 said:


> You got it. NobleSeal TS is a waterproof, crack isolation membrane that also has excellent uncoupling properties. It can be installed with modified thinset and tile can be installed over it with modified too. :thumbsup:


I like the sound of that!


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## bazemk1979 (May 20, 2009)

Why dont you run the marble the old fashion way mudset/level? This way you wont have to install any wonderboard and such,you will only need the metal mesh with the black paper backing and run 1/2" height from the highest spot of the floor.you can also charge much more for this type of instalation.


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## JohnFRWhipple (Oct 20, 2009)

*Modified thinsets*

Installing Nobel TS on the floors and walls allows you like Angus mentioned to use modified thin set. I prefer the Grani Rapid in the wet zone because it does not contribute to efflorescence at all.

With so many complaints online about grout whiting I'm surprised no one has looked into the chance that this is caused from using non modified thin set. I bet that when you use the cheapest product on the block - you get the cheapest end result.

After working with Nobel TS I have no intention of going back to Kerdi unless they change their stand on their installations. Why take the chance of this basic thin set wrecking your instal. Go with the Nobel TS and put technology in your corner!


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## Groutface (Jan 20, 2011)

I'm definitely gonna look into the noble products and their availability through my suppliers.....I agree with the "cheapest" attitude but I'm starting to understand why they use it...will find out the real deal in may,when I take the workshop I've got a loaded barrel full of questions of why and why nots! I still haven't used unmodified on ditra...but I get it....been browsing the noble website and...ME LIKEY WHAT ME SEE!


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## angus242 (Oct 20, 2007)

John, 
Latex additives can leech through grout and cause the same effect. One more reason to use a superior grout like QuartzLock 2. PERM rating of >1%.


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## Munanbak (Jan 19, 2011)

Thanks for all the tips, Should be wrapping up this week.


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## Westcoasting (Feb 21, 2011)

angus242 said:


> You got it. NobleSeal TS is a waterproof, crack isolation membrane that also has excellent uncoupling properties. It can be installed _with_ modified thinset and tile can be installed over it with modified too. :thumbsup:


Hi Angus, is the price comparable to the Schluter products for crack isolation?


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## angus242 (Oct 20, 2007)

Westcoasting said:


> Hi Angus, is the price comparable to the Schluter products for crack isolation?


That will depend on your suppliers. I'd say within $.10


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## Munanbak (Jan 19, 2011)

Sorry to resurrect this old post. 

Thought I would share the pics. 

Job went smooth, everybody happy.

:thumbup:


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## angus242 (Oct 20, 2007)

Munanbak said:


> Sorry to resurrect this old post.
> 
> Thought I would share the pics.
> 
> ...


What did you use for underlayment?


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## Munanbak (Jan 19, 2011)

2x10 joists with 3/4" T&G (I originally thought they were smaller)

1/2" ply, then 1/4" CBU. Crack resistant white mortar. 

...sorry no nobleseal.... felt the crack resistant mortar would be sufficient in this case.


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