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Discussion Starter · #1 ·
First time posting. I am in the middle of a kitchen remodel and would like to lay porcelain tile thru the kitchen and foyer. Existing kitchen floor had 1/2"+5/8"+glued tiles+1/4" underlayment + sheet vinyl on it and the foyer had 1/2" + wire enforced mortar bed with ceramic tile. Everything has been removed back down to the 1/2" subfloor and that is where my question is. How to build it back up. Every tile store I visit gives me a different answer...from gluing & screwing more 1/2" to using 3/4" T&G. Schluter/Ditra gives very specific guidelines on how to add to a 5/8" or 3/4" subfloor but what if you only have 1/2" to start with? The joists are 2x10, spaced 16"OC and span 10.5'. Adjoining rooms have 3/4" oak. I know the tile will be higher but would like to keep the transition to a minimum. I appreciate any advice that will guarantee me a solid base for my tile.
 

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If you want it 100% sure to work out then also get rid of that 1/2, That's all but usless anyway for a subfloor. It will just act as a shim where the joist are.
Useing a Toe Kick saw and an ossilating saw you can cut it out right along the walls and cabinets. While it's out you can check all the joist for condition and out of level or being flat so you do not have to deal with it again once the new subflooring goes in.
Use Advantec 3/4" T & G with constrution adhesive on the joist and ring shanked nails.
Go over that with 3/8 subfloor rated plywood making sure not to have the seams line up with the seams below, nail or staple with narrow crown staples every 4" on the edges and every 6 to 8 in the field. Now your ready for the thin set and tile board.
 

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Tileguy
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joecaption: " If you want it 100% sure to work out then also get rid of that 1/2, That's all but usless anyway for a subfloor. It will just act as a shim where the joist are.
Useing a Toe Kick saw and an ossilating saw you can cut it out right along the walls and cabinets. While it's out you can check all the joist for condition and out of level or being flat so you do not have to deal with it again once the new subflooring goes in.
Use Advantec 3/4" T & G with constrution adhesive on the joist and ring shanked nails.
Go over that with 3/8 subfloor rated plywood making sure not to have the seams line up with the seams below, nail or staple with narrow crown staples every 4" on the edges and every 6 to 8 in the field. Now your ready for the thin set and tile board".

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tjk10,
You should wait for more suggestions before proceeding. What you have so far is very questionable advice.
 

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Tileguy
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Hi TJ, Joe, Bud,

TJ, thanks for the email, but posting here is a better way to get answers, plus you'll get several opinions on how to proceed. (as you can see). :wink:

There's several good ways to do this. Since you told me the 1/2" subfloor is in "relatively good condition", I think you should avoid all the horrors of removing it. (there are many, so let's leave it alone.)

You can install 5/8" exposure 1 ply and then either 1/4" CBU or Ditra. :thumbsup: It would be even better if you went with 3/4" + Ditra. This would give you an even stronger floor and still be 1/16" lower than 5/8" + CBU. 3/4" might be more than you need, but if the extra 1/8" for the ply doesn't matter.......your choice. This method will make your finished floor about 1/2 - 5/8" higher than the hardwood, which isn't bad.

We can fine-tune the ply installation and the rest once you decide which way to go.

Jaz
 

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Discussion Starter · #5 ·
Jaz,

Your 2 options are what I was thinking. I say better safe then sorry and will go 3/4" + Ditra. Does it have to be T&G? That could be a little tricky around some areas like the hall closet & kitchen pantry. Any special thoughts regarding attaching the 3/4....1/8" gaps btw boards, 1/4" around perimeter, offset seams from 1/2 subfloor, maybe even predrill holes so both layers are pulled down tight at the joists?

Thanks,

TJ
 

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Tileguy
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I agree with Bud in every case. But, sometimes we have to break the rule about not fastening into the joists.

Normally the second sheet gets screwed into the subfloor only as mentioned earlier. But, because it's old 1/2" in this case, and a screw may not have enough bite, you might have to disregard that rule. See how well it holds first, then add additional screws if necessary. You'll be alright cuz Ditra will give you plenty of uncoupling.

Use quality flooring screws, not cheapo drywall screws.

Jaz
 

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Discussion Starter · #8 ·
Jaz & Bud,

Thanks for the help. My instincts (or the engineer in me) tell me securing 3/4 to 1/2 is a little risky and by securing it to the joists I am basically ignoring the 1/2 layer. Obviously it will provide some additional strength but not as much as if it were in the right order of 3/4 and then the 1/2 but that's the cards I have been dealt.

Thanks for sharing your opinions and wisdom.

TJ
 

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Tileguy
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tjk10 said:
My instincts (or the engineer in me) tell me securing 3/4 to 1/2 is a little risky and by securing it to the joists I am basically ignoring the 1/2 layer.
Exactly right! :thumbsup:

Jaz
 
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