Above grade, wood subfloor, hardy board or schluter w/ tile

10 years ago

I tried to explain it in the title but, i have a kitchen this is not on a slab. It currently has a plywood subfloor with laminate glued to it.

I would like to avoid ripping up the subfloor, but at the same time want to make something that lasts.

What is my best option, hardy board ontop of the current floor, or ditra on top of the current floor and then lay tile ontop of it?

I also need to mention there is currently a dip in the center of the floor where our island will stradle, at one point a good 3/4 inch dip.

I've had someone under the house and said they could jack it up and install a support beam, or could i float extra mud under the schluter or under the hardy board, which ever is recommended.

Sorry for the log winded post just curious on what the best way to approach this is.

Thanks,

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Comments (3)

live_wire_oak
10 years ago
The basics first. Why is there a dip in the center? It sounds like a support beam is damaged. That would be the absolute first priority. Then you need to know your joist depth, spacing, and span in order to calculate the deflection. A tile floor needs to be much stiffer than one for wood or carpet. What size tile? Larger tile or stone also needs a much stiffer floor than does smaller tiles or porcelain.
davidro1
10 years ago
Ditto.

Biggest question:
"Why is there a dip in the center? It sounds like a support beam is damaged. That would be the absolute first priority. Then you need to know your joist depth, spacing, and span in order to calculate the deflection. ..."

You have to know more about the foundation. You've "had someone under the house", so this means there is no basement. Other than that you have provided no information. Letting someone "jack it up and install a support beam" is wishful thinking; it might work, it might not. More knowledge first.

In other words you are asking all the wrong questions if you ask about the laminate or the single layer of plywood, or about adding a layer of cement-based tile board or plastic membrane on top of the subfloor.

If you are willing to live with hairline cracks in the tiles, continue as you are thinking. If you want to remove that risk, the only thing to focus on is the solidity/rigidity. Then, it becomes almost insignificant whether you rip up the laminate or not. I'll bet you will end up choosing to install another layer of plywood on top of the existing plywood subfloor, screwed into the plywood not into the joists. Then, ditra or anything like it, on top of the two-layer subfloor.

You haven't said what is under the subfloor in terms of airbreak and thermal insulation. This is a big thing. Otherwise the cold from the outside gets into the tile floor, and the mass of thinset cement and porcelain become a radiator of Cold, radiating Anti-heat, radiating Negative Heat. This is not comfort.

Hth
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When we go a front loader I read of problems some of them had on anything but a concrete basement floor. We had a carpeted sub floor on a crawl space with normal joists. To improve stability I merely cut a 4x8 piece of A-C grade exterior plywood to fit under both the washer and dryer. i figured it would srpeat tha weight over more joists and add stability. We had it installed over the very short napped carpet with ring nails and then put a Hardy board underlayment on both the rest of the carpet and our "island". Then we had porcelain tile installed. This has worked just as we expected and is doable and cheap.
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brickeyee
10 years ago
Tile needs a solid base to last very long.

What size tiles, what joist span, what joist size, what sub-floor thickness and material?

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Above grade, wood subfloor, hardy board or schluter w/ tile

Comments (3)

live_wire_oak

davidro1

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