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Profane 01-23-2008 10:20 AM

Tile laying question
Heya all,
I am new here and to home improvement. I have a room that I want to lay some (I think its Ceramic) tile down. I have what looks to be a 3/4 inch plywood sub floor. Its a bit flimsy so I figure I need to add something on top to help strengthen it. My question is this...What should be laid down on top of the sub floor and how should it be attached. I have read just lay down a thin piece of plywood and then slap your tile down on that with thinset, but I have also read that you need to lay concrete? board down and then your tiles. I guess I am really looking for a step by step process of what "layers" /steps need to happen from the sub floor to the actual tile.


Rehabber 01-23-2008 11:30 AM

First, you need to know the joist material, joist size, joist spacing and the length of the span between the joist supports so the deflection can be calculated. Then you will need to know exactly how much and what kind of material is on top of the joists. (drill a small hole in it and check the total thickness. Post back and further help will come :thumbup:

Profane 01-23-2008 11:41 AM goes ;)

There is a slab...with what appears to be (1x2?) laid flat against the slab...on top of that its 2x4s on their side. The 2x4s have been slotted on one end to keep them a hair off the slab. The space between the joists is about 14 inches.


Rehabber 01-23-2008 01:56 PM

Deflection will be OK Next step is what kind of material and how thick is on top of the joists?

Profane 01-23-2008 02:23 PM

Thanks for the reply Rehabber....the top of the joist is maybe an inch and a half...tops...I am at work so I am going from memory. The joists themselves are basically 2x4s on their far as what matieral...I am assuming your asking what the 2x4s are made of? or the sub knowledge is just wood for the 2x4s and plywood for the subfloor

I have been trying to figure this out all day what the best practice for this will be. Right now I am leaning on tearing out the entire floor in the room, replacing it with exterior grade plywood...maybe 3/4 inch...lay a think layer of thin set and screw a cement backer board. Then thin set and tile. Is that the basic process?

Rehabber 01-23-2008 02:47 PM

You will need a minimum of 1 and 1/4 inch of plywood subfloor. Then put down backerboard with thinset as recommended by the backerboard mfg. check the mfg website for all installation instructions. You are then ready to tile.

Profane 01-23-2008 03:11 PM

Gotcha! Thanks a ton for your help...One last question. I believe I have the space to build up to 1 and 1/4 inch, but can I lap another piece of 3/4 inch on top of the existing and then start the backer board or should I really tear it up and put in once piece...

JazMan 01-23-2008 03:31 PM


Maybe you missed it (?) but he has a slab as a floor with a concoction's of wood over it. Hence why his floor is flimsy. Maybe start over?


Profane 01-23-2008 03:49 PM

This house is a Cobbled together mess in my opinion. And actually I think the plywood is 1/2 inch now that I think about it. The sub floor is actually sandwiched between 2x4s so I have to use a saw to cut it out...and its nailed about 4 inches inside the wall making it unaccessible. To do everything the right way, I would need to gut the room...and I am REALLY trying at all costs to avoid that. I was planning on cutting 2x4 and making small boxes along the wall so I can actually nail the "new" floor in place. I have some space to work with so adding a bit of hight to the floor wont matter all that much.

I was basically just trying to make this room into a first floor laundry room but the more I dig into it, the more its becoming a nightmare.

Rehabber 01-23-2008 04:21 PM

Could you remove all the floor to concrete, tile on the concrete and use tall baseboard to cover the gaps?

Profane 01-25-2008 05:30 AM


Originally Posted by Rehabber (Post 91283)
You will need a minimum of 1 and 1/4 inch of plywood subfloor. Then put down backerboard with thinset as recommended by the backerboard mfg. check the mfg website for all installation instructions. You are then ready to tile.

I don't think going down to concrete will help me...If I do that I will have to tear out the walls ....and thats something I am honestly afraid to do if only because I am guessing I am going to see some bad stuff :( lol.

Ok last question I think...My plans are being finalized...and I think its a solid plan. you mentioned I need 1 and 1/4 inch of that just one piece...IE they make 1 and 1/4 plywood? I went out to our local lowes and I only saw 3/4 inch...I wasnt sure if I need to keep looking or if I am just not quite understanding the "subfloor" or whatever is under the tile..

EDIT: By the way...thanks a ton for helping me out on this...I actualyt too some before pictures and once I find a place to host them I will post them up.

JazMan 01-25-2008 09:11 PM

Any type of wood flooring over concrete does not work long term. As you already know it's going to twist and buckle, shrink and expand. You need to rip everything out and go over the slab.


Profane 01-25-2008 10:28 PM

Its not directly on the slab......but again...I jsut want to know at this point if I slap 2 3/4 sheets on top of each other...

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