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Can I use self leveling underlayment on top of 3/4" OSB for a tile bathroom?

Can I use self leveling underlayment on top of 3/4" OSB for a tile bathroom?


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Old 02-06-10, 09:12 PM
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Question Can I use self leveling underlayment on top of 3/4" OSB for a tile bathroom?

I am redoing a small bathroom (maybe 5'x8' or so) in a 1922 house and ripped everything out and sistered the floor joists because of wood rot but the floor did not come out level due to some miscalculations.

It is 1" higher on one end. I didn't realize this until it was too late and the 3/4" osb, 1/2" osb, and 1/2" concrete board were all laid down.

I can not redo the floor joists so I want to rip out the 1/2" osb and 1/2" concrete board and then use a self leveling underlayment on the existing 3/4" osb to level the floor out and bring it back up to the current height.

Then I'd like to lay 1" porcelin hex on it.

Would there be any problem doing this? Is the floor going to be strong enough? I want this floor to last for a looooooong time.

If I add anymore osb or plywood, the floor will be higher than the hallway floor (which it probably will be by about 1/4" anyways).
 
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Old 02-07-10, 11:29 AM
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You can't lay the tile directly on the wood, so lasting a looong time is out of the question. What is the joist spacing?
 
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Old 02-07-10, 04:25 PM
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the joists are 2x8 sistered to the old 2x8 joists. I think the joist spacing is about 16"

I wanted to put the tile directly on the self leveler, not directly on the osb. Would that work?
 
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Old 02-08-10, 01:00 PM
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[The most important thing here is that you have corrected the reasons why the floor is so out of level. It sounds like you have already done this, yes?

QUOTE]I wanted to put the tile directly on the self leveler, not directly on the osb. Would that work? [/QUOTE]

You can do it that way, but it would be mucho expensivo. You would have to add aggregate to the slc in the thicker areas or do several pours. You could also install build up the low side with plywood, slc everything level and then install a membrane line ditra over the slc.

A better way to do this would be to mud the entire floor. If you will be removing 1/2" of plywood and 1/2" of cement board, it sounds like you can afford the height needed. The mud should be at least 1 1/4" thick at the highest point, and can be as thick as need be at the lowest point to get the floor level. Easier to work with and a fraction of the cost.

How will leveling the floor affect other things like the doorway transition to the adjacent room, the closet flange height, baseboard heat etc.
 
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Old 02-11-10, 08:49 AM
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I can't mud it because the slope is still there.

The whole problem is that the floor joists are not level because the sloping floor was not accounted for when the new ones were put in. The house is old and the original floor was sloping.

At this point it would be a HUGE job to redo the floor joists and I just don't have the time or energy to do that unless there are no other options.

It would proably be about $100 for a few bags of self lever. I can live with that as long as the floor is fixed correctly.

If I add 1" overall to the subfloor, plus tile, the overall bathroom floor will be about 1/4" to 3'8" higher than the hallway floor. I'm redoing the whole bathroom so I'm basically starting from scratch with everyting.

What would the membrane that you suggested do? I did research on that but am not real clear. Would that just help to eliminate cracking due to flex? How much height does it add to the floor?


Originally Posted by HeresJohnny
[The most important thing here is that you have corrected the reasons why the floor is so out of level. It sounds like you have already done this, yes?

QUOTE]I wanted to put the tile directly on the self leveler, not directly on the osb. Would that work?
You can do it that way, but it would be mucho expensivo. You would have to add aggregate to the slc in the thicker areas or do several pours. You could also install build up the low side with plywood, slc everything level and then install a membrane line ditra over the slc.

A better way to do this would be to mud the entire floor. If you will be removing 1/2" of plywood and 1/2" of cement board, it sounds like you can afford the height needed. The mud should be at least 1 1/4" thick at the highest point, and can be as thick as need be at the lowest point to get the floor level. Easier to work with and a fraction of the cost.

How will leveling the floor affect other things like the doorway transition to the adjacent room, the closet flange height, baseboard heat etc.[/QUOTE]
 
  #6  
Old 02-11-10, 10:22 AM
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I can't mud it because the slope is still there.
You could mud the floor. It would just be thicker on one side of the room than the other.

What would the membrane that you suggested do? I did research on that but am not real clear. Would that just help to eliminate cracking due to flex? How much height does it add to the floor?
The membrane is an uncoulpling membrane. It basically isolates any horizontal movement from the subfloor from transferring to the tile. If you are going to slc the whole floor, you don't really need it.
 
 

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