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Teikas Dad 12-11-2010 06:03 PM

Leveling an uneven bathroom floor - HELP!
I'm in the process of remodeling one of our bathrooms. It's not a large bathroom, the floor area is 95" X 65". The old floor was 1X1 tile over a 1" thick mortar bed. The mortar bed was laid on top of black tarpaper, over the plywood subfloor.

We got all the old tile and mortar out so we're down to the plywood subfloor. I'm going to tile again so I'm going to install 1/2" plywood over the subfloor and 1/2" Durock over the plywood, then tile.

The problem I have is that the floor slopes 3/4" from one side to the other (across the 65" side). The floor beams run perpendicular to the slope.

I was thinking about ripping some 6" wide strips of 3/4", 1/2" and 1/4" plywood and screw them down on top of the subfloor directly over the floor joists. Then put the new 1/2" plywood on top of that. Would that work? It would level the slope out for me but I'm worried about the gaps between the plywood strips. Should I fill the space/gaps between them with floor leveling compound before screwing down the new plywood? I don't want the floor to flex and crack the tile. (I'm replacing the 1X1 tile with 12"X12" tile.


JazMan 12-11-2010 08:00 PM

No, that will not work. 1/2" ply is way too thin, the floor will feel like a trampoline. What you really need is to re-do the floor the way it was. If you wanna try it let us know and we can help you. Otherwise your method has merit.

I would make the strips narrower than 6" if the floor's slope is not consistent, maybe as narrow as 2", otherwise 6" is ok, and you will need a 3/4" t&g plywood subfloor. Also you should use 1/4" concrete backer, no need or benefit to using 1/2". Actually Ditra would be even better, and it only raises the floor 1/8" if that matters.

3/4" in 5 and a half feet is a big slope, did the house sag? Have you considered jacking the darn thing up? You will note from the above that the low side of the room will be raised about 1 3/4" with 1/4" board and the other side will be an inch higher from your present subfloor which I think is what you want.


Teikas Dad 12-11-2010 09:44 PM

No, the house didn't sag, it's just that one section of floor. There's really no way to jack it up...the house is raised ranch with the basement completely finished off. I think it was built that way (in 1968) as the old tile floor was level on the surface, I guess they made up the slope difference with the mortar under the tile.

The portion of the floor that slopes the most is going to be under the vanity. The area in front of the tub (tub is an alcove tub off to the side of the floor area) is level, so the area where you walk in the door, walk to the tub and toilet is level, the slope actually starts about halfway across the width of the floor.

Would putting a floor leveling compound between the plywood strips help prevent the floor from moving?

oh'mike 12-12-2010 05:58 AM

The safe and sure method of leveling that would be to expose the floor joists and sister in some new joists--even 2x6 might be all that is needed--If nailed well-----Laying tapered strips seldom works--

The time you spend attempting that would be better spent removing the sub floor and fixing the builders mistake---Mike----

KCB 12-12-2010 07:26 AM

Your strip method will work .Ive done it before but i used 2x4 ripped to fit each joist then pre-drill glue and screwd them down .BUT you need 3/4 plywood instead of 1/2.Theres been no issues in the floor ive repaired for 8 years now.The customer was so happy i saved them several hundreds of dollars.
Would Ditra help in your hieght issue using 3/4 plywood instead of 1/2" subfloor?

JohnFRWhipple 12-12-2010 08:39 AM

Levelling an un level floor
A 3/4" change is quite extreme over such a short span. IS your level true?

What is the original subfloor material? Is it Ship Lap or Plywood? How thick?

Do not run out and purchase Ditra or cut up strips of ply that will do you no good.

Did your old floor have chicken wire or expanded metal lathe in the concrete top coat?

What is the span of your floor joists? What is the distance between them?

Until these questions are answered there should be no "How To" advice offered...

Was the floor always this much out of level?


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