# Tile underlayment question



## SKC (Apr 7, 2010)

I will be renovating a small kitchen soon, over an existing 3/4 T&G standard 2 1/4" width fir flooring, sitting directly on floor joists, 16" O.C. (no sub floor). So this flooring will act as sub floor.
Will be installing tile floor over this, obviously need an underlayment.
I would like to hear other opinions on what would be best and thinest underlayment for this. (trying to keep as thin as possible).
I am thinking 1/2" plywood, 1/2" cement backer any better for this particular use ? or any better ideas ?.


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## angus242 (Oct 20, 2007)

1/2 exterior ply, Ditra.
Use Kerabond mixed with Keralastic to install Ditra over the ply. Use Kerabond mixed with water to install tile over the Ditra.

Collect your check!


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## SKC (Apr 7, 2010)

angus242 said:


> 1/2 exterior ply, Ditra.
> Use Kerabond mixed with Keralastic to install Ditra over the ply. Use Kerabond mixed with water to install tile over the Ditra.
> 
> Collect your check!


 
Angus thanks, was hopeing to get response from you.

I was unfamiliar with these products before, read the info at website.
I'm guessing your reccomending this because of T&G as subfloor? or
would you suggest same if subfloor was 3/4" plywood with the 1/2" as underlayment ?. Is it in your opinion worth the extra cost as opposed to just tileing over the 1/2" ext. ply. using maybe flexbond, or is this way a high risk of cracking ? I have seen plenty of tile over 1/2" on 3/4" ply. subfloor. without problems. 
I like to know why I do a job the way i'm doing it (I usually prefer the best way)


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## opiethetileman (Apr 7, 2005)

or you can use laticrete 252 to adhere the ditra to floor or subfloor and use laticrete 272 the adhere the tile to the ditra. but either is correct. Some of us dont know mapei lingo I only know laticrete.


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## angus242 (Oct 20, 2007)

SKC said:


> I'm guessing your reccomending this because of T&G as subfloor? or would you suggest same if subfloor was 3/4" plywood with the 1/2" as underlayment ?


For the most part, with so many newer homes be built to minimum specs, adding 1/2" EGP over the subfloor is usually a very good idea. There are cases when the house is framed without 14' joist spans where the 3/4" T&G is totally sufficient.





SKC said:


> Is it in your opinion worth the extra cost as opposed to just tileing over the 1/2" ext. ply. using maybe flexbond, or is this way a high risk of cracking ?)


I do not see it as an extra cost. I see it as a necessity. TCNA MINIMUM recommendation for tiling directly over ply is 1 1/4". That's 3/4" + 5/8". I also think going directly over ply is an unnecessary risk. There is no other tile underlayment that is better than Ditra (IMO). 

To me, Ditra is the standard/norm/minimum for a floor in 99% of my situations. 

While guys successfully use Custom's thinset(s) regularly, I prefer Mapei products.


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## opiethetileman (Apr 7, 2005)

I agree with angus ditra is the way to go by far. But in florida there is not alot of above grade floors going on. Most of my work is slabs. Custom makes great stuff so does mapei. I just like the blue and silver laticrete. We all have our favorites by far.


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## SKC (Apr 7, 2010)

Again thanks to angus and opi
I never doubted the 1/2" over subfloor, I was just questioning the ditra as being needed (for the cost) You answered that clearly.
I accept it and will do it that way. Thankyou for your expertise, thats why I asked here, I beleive this site has some real quality contractor people worth getting opinions from.

Hope I can be of use to you some day, Thanks guys.

Sheldon


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## angus242 (Oct 20, 2007)

Ah but let us not forget the benefit to using Ditra over a slab...

Ditra vs Liquid membrane:
Waterproof? both - check!
Crack Isolation? both - check!
Allows the slab to breathe? both - NOT check!

Only Ditra with its waffle design will allow moisture from underneath to evaporate. A liquid or even sheet membrane will not do the same.

Ditra over concrete? Yeppers! :thumbsup:


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## ROVACON (Apr 19, 2010)

SKC.....once you go ORANGE you will never go back...:no:


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## JazMan (Feb 16, 2007)

I highly recommend Ditra too, it's a great way to go. 

I wouldn't be so concerned which brand of thin set you use, just use the correct type. I mostly use Laticrete and Hydroment. Hydroment makes Ditraset which is designed for use over Ditra and is a very high quality unmodified thin set. 

By the way it's constructed, your house must be kinda old. Have you checked that the joists are suitable for tiles? Have you narrowed the tile selection yet?

Jaz


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## opiethetileman (Apr 7, 2005)

I went GREEN and got very mean......... yeah I agree ditra is not just for wood subfloors. It can be used over a concrete floor as well. Just havent been able to get a job to sell with it yet.


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