Help with underlayment

[danmendez29]

Hey guys im looking to get some advice on what i should do for the underlayment for a tile floor in my kitchen. I know i need to have a cement type board down before the tille, but manufacture says to have 5/8 minimum plywood subfloor before installation. the house i have was built in 1850 and subfloors throughout house are 5/4 then have a wood "plank" floor on top of the 5/4. my question is am i good to use what's already there as the subfloor or do i absolutely have to add another layer of 5/8 or 3/4. obviously this isnt a way i want to go. i have attached a picture of the kitchen floor.

[jadnashua]

You need at least 1/2" of ply. TO keep the buildup lower, you could go with a membrane versus a cbu product. FWIW, planks just move too much, and you need something more substantial than cbu on top of them for stability.

Have you checked your floor joists for strength? Are the planks T&G?

[cx]

Welcome, Dan.

You'll need to remove that top layer of flooring, which in your photo appears to be what would usually be called strip wood flooring rather than "planks" as you suggest.

Then you would need a minimum of nominal 1/2" plywood over the 5/4 board subfloor before your tile substrate.

The minimum nominal 5/8ths" plywood requirement you see for most CBU manufacturers presumes that material as a single layer subfloor, which I would not recommend tiling over on a bet.

My opinion; worth price charged.

[danmendez29]

i was afraid that was going to be the answer. Not sure what i want to do now. forgot to mention this is a rental property and afraid of putting too much money into it.

[cx]

A tile floor doesn't care who lives in the house, Dan, it should be installed the same way regardless the intended user. Really it should.

My opinion; worth price charged.

[risotttto]

CX has a point, If you own the building, think of any future costs to repair a crappy underlayment when you have to rip everything up again 5 years down the line because you didn't put the money and effort in up front.