Prep subfloor for tile

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Prep subfloor for tile

Post by iDiffer » Tue Mar 06, 2018 10:21 pm

Hello. I want to lay tile in the kitchen. Prior owners had carpet that I removed and believe there is 5/8 in plywood on top of subfloor. Some call it underpayment and others call it two-layer subfloor. The problem I have is that my top layer is wavy with dips 3/8 in every 3 feet or so parralel to joists. Question is how to go about it to flatten it so I could install backer board and tile? Some say to use self-leveling compound; others say to remove top layer and lay new plywood as it sounds like top layer is warping and putting new plywood would make it flat again. Perhaps all that moister and water leaks when there was a carpet deformed hebtop later. (I know what you might ask, why was there a carpet in the kitchen? Who knows). So at this point I am confused. I am wanting to do it right so the job lasts. On the picture, I pensiled in the middle where one of the dips was, and then parralelcto it, it seems to repeat again.
image.jpg (159.13 KiB) Viewed 243 times
Any input is greatly appreciated.

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Re: Prep subfloor for tile

Post by Shannon » Wed Mar 07, 2018 7:13 am

You could lay selfleveler in the lowest areas and then use mortar and 1/2" cement board over the entire floor or self leveller in low areas and use Ditra uncoupling membrane instead of cement board.The Ditra will give a little less overall thickness once installed compared to the cement board.
Be sure to use the proper primer before the self leveler to help it adhere to the wood.
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Re: Prep subfloor for tile

Post by marks1 » Tue Mar 20, 2018 6:49 am

I think you should remove top layer and go for stone or tile flooring. You can consult one of the flooring companies for it. Also you can have another option of laminate flooring. Just check out this three type of flooring and which ever suits you select it. Through this you will have a flat structure as well as you wont need to worry about it for long run.

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Re: Prep subfloor for tile

Post by Rockhound » Sun Apr 15, 2018 10:27 am

The picture makes it look like Luan. If it is, I would remove the Luan. Install cement board. If it's plywood, then I would still remove it and install cement board. Most tile manufacturers will tell you the purpose of the cement board is to act as a leveler and less so as adding to structural integrity of the flooring. I did this 15 years ago in a similar situation and it continues today as strong as can be. Remember that when installing the cement board to trowel on a layer of thinset between plywood and subfloor. This is used to fill voids and is an important step. My floor still looks great, no cracks, and feels great, nice and solid.

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