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Unread 04-18-2008, 11:03 AM   #1
jaymay75
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Leveling Sub Floor - need advice

I am putting 18" x 18" Travertine tile down in my bathroom. The house is about 60+ years old and there is a 1" dip in the floor of the bathroom. The bathroom is 15'x6'. The dip runs the lengnth of the floor.

The original floor has a 1/2" plywood covering it from a previous remodel. I came in and put a bed of thinset down with 1/2" hardiboard on top. Then I realized the dip in the floor.

Should I:
- Use a self Leveling product to level out this dip. If so could you provide the best product to use.

- Should I just lay a bed of thinset down in the dip and screed it out.

- Should I lay a bed of mortar down in the dip and screed it out.

Thank You,

Jason
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Unread 04-18-2008, 11:19 AM   #2
Dave Taylor
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Hi Jason........

You should do 'none of the above' until..........

you know that your floor substructure is suitable for a natural stone covering and..... you have told us what is above those floor joists besides 1/2" ply + thinset + 1/2" CBU.

Check out the (Ta Da) whirl' famus' Deflecto tool at the top of this page, measure your joists accordingly, then input the results into the Deflecto tool.

Then..... tell us what your joist measurements are, tell us about the condition of your joists and.... tell us about your subfloor including all its various underlayments.
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Last edited by Dave Taylor; 04-18-2008 at 11:27 AM.
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Unread 04-18-2008, 11:34 AM   #3
jaymay75
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Thank you for using the John Bridge Forums Deflect-O-Lator :-)

For joists that are SYP or Douglas Fir, in good condition, 10 inches tall, 2 inches wide, 16 inches on center, and 16 feet long between supports, the deflection calculated is 0.437 inches.

This translates to a deflection of L / 439.

Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Ceramic tile, Congratulations!


I guess I'm sistering some joists
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Unread 04-18-2008, 12:18 PM   #4
Mike2
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In addition to that, Jason, 1/2" plywood sub-flooring is not sufficient for tile. Absolute minimum for ceramic tile is 5/8". Natural stone like travertine needs a 2-layer plywood floor, 1-1/8" total thickness. By the way, CBU adds no structural stiffness to a floor and doesn't count towards those sub-flooring requirements.
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Unread 04-18-2008, 12:28 PM   #5
jaymay75
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Yep, I got 3/4 hardwood floor, 1/2" plywood on top of that from a previous remodel, then I put 1/2" hardiboard on top of that set in thinset.

good??
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Unread 04-18-2008, 12:32 PM   #6
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Any reason you are using 1/2" hardi ? CBU adds no structural integrity so unless you are trying to raise the floor, I would go with 1/4" CBU. Remember that hardi tends to be thirsty.
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Unread 04-18-2008, 01:03 PM   #7
jaymay75
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It was a mistake - I didn't notice the 1/2" plywood down until I had a few pieces of hardiboard on. floor will just be 1/4" thicker.

I didn't notice the floor saggin that much either, until after hardieboard was down.
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Unread 04-18-2008, 04:57 PM   #8
jadnashua
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Well, the 1/2" ply MIGHT be enough to decouple things, but I kind of doubt it. While the hardwood may be stronger, it MOVES. Tile doesn't like movement. Do you know what is under the hardwood? Is that directly on the joists or subflooring, or is there more structure underneath it?

If there's more stuff under it, then you've probably got enough depth available to do a full mudbed...then you can get it dead level.
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Unread 04-20-2008, 08:00 PM   #9
jaymay75
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OK, I sistered all the joists and they are rock solid. 16' 2x10's.

I still have about just over 1/4" dip in the floor. The vanity that we have sitting in there does not sit level.

To flatten out the dip - I need advice as to whether to use the self Leveling Topping or if I should just put a layer of thinset down and screed it level, let it dry then put the tile down.

Any and all advice is much appreciated.

Jason
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Unread 04-21-2008, 07:01 AM   #10
jaymay75
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Anyone have any advice - Thank You,
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Unread 04-21-2008, 12:08 PM   #11
jaymay75
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Self Leveling concrete

As posted in my other post, I have a 1/4" dip in my bathroom floor. I gutted the room below my bathroom and sistered all of the joists so the floor is strong enough for stone tile. I am putting down travertine and need to know how to fill in this 1/4" gap. Should I use self leveling concrete, or just put a layer of thinset down and screed it off. Any tips, brands, etc would be really helpful.

Thank you,

Jason
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Unread 04-21-2008, 12:38 PM   #12
bbcamp
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The trouble with SLC is that it wants to find it's own level, whereas your floor may not be level, just needs a little flattening. Use a good modified thinset and screed the low area. Install your backerboard first, if you haven't already.
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Unread 04-21-2008, 01:00 PM   #13
jaymay75
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Any brands on a modified thinset that should be used?

Thanks for the advice.

Jason
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Unread 04-21-2008, 01:14 PM   #14
bbcamp
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Versabond will do.
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Unread 04-21-2008, 01:22 PM   #15
jaymay75
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Is versabond better or worse than Mapei UltraFlex II

Thank you,
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