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Rclancyc 07-30-2012 04:04 PM

Floor leveling debacle
Hello all, we are in the process of remodeling our 7'X7' bathroom. I ripped out the old subfloor, replaced a number of joists, and now have 3/4 t&g plywood subfloors with 3/8th inch plywood as an underlayment. The house is 60 years old and the subfloor despite our best efforts has a ridge in the center of the room. it slopes a 1/4" to the west and 1/2" to the east. The fall in the floor is over 3' to the west and 4' to the east.

I plan to use ditra under slate tile. I went to the store and purchased metal lathe and self leveling compound. But when I got to thinking about it, I balked at pouring the whole floor.

I am concerned that if i put lathe over the entire floor, the concrete needs a minimum thickness of 1/8" above the lathe per instructions. The result would the unfinished bathroom floor would be the same height as the finished floor at the threshhold. Plus add another half inch for the ditra and another half inch for the tile and I have a bathroom that will want to spill water into our bedroom.

I am curious about how all you pros would handle this? I have thought about trying to level it out with an extra thick layer of thinset before the ditra, but it sounds like it is only suitable up to 3/16" if ever (thinset for a reason). I have also thought about using SLC on the sides independently, and leaving the ridge bare, but then i would have to worry about using different type of thinset for the wood portion along the ridge and the concrete portions on the sides. I have also thought about just putting the grout line on the ridge and living with it.

This simple problem has turned into a conundrum in my mind. Thank you for any help in advance!

shbhalla 07-30-2012 04:15 PM

I have the same issue but on a bigger scale. My kitchen is 10' x 17' and have a similar situation. (read thread

I am calling some contractors in to take a look. I will let you know what the contractors have to say.

I think, you need to tell us what kind of floor is this and if you have access to the joists. You also need to tell us what kind of joists are these. pictures will help as well.


joecaption 07-30-2012 04:28 PM

Two late now but the floor joist should have been made to be level and flat before the subfloor went in.
Shimming, sistering, planing whatever was called for.

Rclancyc 07-30-2012 04:40 PM

thanks for the replies. Believe it or not, we actually did shim the joists and plane the tops off of some of them that we noticed were high (including the ridge). Our rudimentary way of measuring the flatness of our joists was insufficient. The good news is that the floor is structurally sound and the ridge at this point is from the old joist that is a true 2x8 rather than 7.25 and us not planing it enough. Would you recommend using the SLC over the entire floor or is there any chance the same could be accomplished with a thick coat of thinset under the ditra and an eye for detail? I'm not quite as concerned about the aesthetics as I am the integrity of the tile after its been set.

JazMan 07-30-2012 07:32 PM

Where did you get all these thicknesses? Who told you Ditra installed is 1/2". Ditra installed is 1/8", total. Ditra is 1/8" and thin set adds nothing. Did you check the joists deflection in a span chart? Natural stone requires a much stiffer floor than regular ceramic does.

You need to fix and make the floor flat if the joists' are stiff enough. Otherwise nix the slate. Yes you need to use SLC to make it flat.


Two late? heheheehehehe

Rclancyc 07-31-2012 09:27 AM

thanks jazman, I really like what you have to say and have used some of your suggestions to other members already! The thicknesses were more of a ballpark estimate. Projects always go smoother in my mind than in so I imagined laying heavy layer of thinset before the ditra. Still aggressive on my part and duely noted. I have checked the span charts and should be fine. Joists are 2x8 16" OC spanning about 6.5' between beams. I will use the SLC and flatten it out that way. I figured it would come to this but thought that maybe I had overlooked a more suitable method. Thanks again for the help guys!

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