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Old 02-13-2015, 02:05 PM   #1
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Subfloor levelling question


Hi all,

I am remodeling my bathroom. There used to be a drop in type of tub as shown here:



I plan to put a regular tub and as a result I need to patch the large hole in the subfloor as shown here:



My existing subfloor is 1-1/8in plywood laid on top of 4x6 joists 4 feet in the center

I started patching the hole with 4x6 studs perpendicular to an existing floor joist as shown here:



However, when I layed the new plywood on top for dryfitting, I noticed that the new plywood thickness is slightly smaller... (less the 1/8th)



I was wondering if I could add stappled felt/tar paper along the new and existing joists to make up for the height difference (I don't think it would compress much).

The new plywood will be covered by the new tub and some tile (with 1/4in backerboard).

Any comment or other idea? (I 'd prefer avoiding SLC if possible)
Thank you for your help,
John

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Old 02-15-2015, 06:46 PM   #2
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Subfloor levelling question


If it is being covered with the tub I don't think you need to worry about it. If part of it shows in front of the tub tile mortar will cover it and allow you to level the floor. If you really want to fix it then I don't see any problem with the tar paper as you mentioned. However it is very thin. You could try drywall shims. They have been compressed when they were made so they should not compress any more. I have used them to level floor joist in a house I built. Another option and probably better would be thin plywood say 1/8.

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Old 02-16-2015, 05:59 PM   #3
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Subfloor levelling question


In cases like this, I've occasionally used leveling compound with good success. It can be feathered paper-thin with a float if needed
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Old 02-17-2015, 11:35 AM   #4
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Subfloor levelling question


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Originally Posted by RMK View Post
If it is being covered with the tub I don't think you need to worry about it. If part of it shows in front of the tub tile mortar will cover it and allow you to level the floor. If you really want to fix it then I don't see any problem with the tar paper as you mentioned. However it is very thin. You could try drywall shims. They have been compressed when they were made so they should not compress any more. I have used them to level floor joist in a house I built. Another option and probably better would be thin plywood say 1/8.
Hi thank you for your message. Shouln't I be concerned with drywall shims that the cardboard might get wet and breaking up later since the tile might not be 100% waterproof?

John
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Old 02-17-2015, 01:13 PM   #5
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Subfloor levelling question


You will be able to stick an elephant in that tub.

One question,,, How long and wide is that area.?
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Old 02-17-2015, 01:14 PM   #6
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Subfloor levelling question


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You will be able to stick an elephant in that tub.
Better safe than sorry
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Old 02-17-2015, 03:30 PM   #7
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Originally Posted by southernboy View Post
In cases like this, I've occasionally used leveling compound with good success. It can be feathered paper-thin with a float if needed
like Ardex. i would not shim with felt paper, it can compress over time.
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Old 02-17-2015, 04:03 PM   #8
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Subfloor levelling question


What kind of flooring are you going with? If its something with a motor bed just put it a little thicker next to the tub, if not use a floor leveler like somebody else suggested
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Old 02-17-2015, 04:19 PM   #9
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Originally Posted by scottktmrider View Post
What kind of flooring are you going with? If its something with a motor bed just put it a little thicker next to the tub, if not use a floor leveler like somebody else suggested
I will put tile (Plywood > thinset > hardibacker 1/4 in > thinset > 1/4 in tile)

and this bathtub:
http://www.us.kohler.com/us/Expanse%C2%AE+60%22+x+32-38%22+curved+alcove+bath+with+integral+tile+flange +and+left-hand+drain/productDetail/Soaking+Baths/427501.htm


The covered hole is 48 in wide while the tub at its largest is 38 in.

Concerning the bathtub installation, it has 4 legs and I am still debating whether I should set it on a mortar bed or on insulation foam (seems less messy)

John
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Old 02-17-2015, 04:22 PM   #10
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Subfloor levelling question


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Originally Posted by concrete_joe View Post
like Ardex. i would not shim with felt paper, it can compress over time.
Hi,

What kind of shim would you recommand (I need around 1/8in) that would be incompressible?

I can't find plywood this thin at Lowes or Home Depot
John
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Old 02-17-2015, 04:41 PM   #11
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Subfloor levelling question


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Originally Posted by Slashp View Post
I will put tile (Plywood > thinset > hardibacker 1/4 in > thinset > 1/4 in tile)

and this bathtub:
http://www.us.kohler.com/us/Expanse%C2%AE+60%22+x+32-38%22+curved+alcove+bath+with+integral+tile+flange +and+left-hand+drain/productDetail/Soaking+Baths/427501.htm


The covered hole is 48 in wide while the tub at its largest is 38 in.

Concerning the bathtub installation, it has 4 legs and I am still debating whether I should set it on a mortar bed or on insulation foam (seems less messy)

John
Long ago I had an acrylic tub with foam insulation under it instead of a mortar bed. I hated it. It squeeked and flexed. Maybe they do foam better nowadays but if I had to choose, I'd go with mortar.
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Old 02-17-2015, 05:11 PM   #12
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Subfloor levelling question


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Long ago I had an acrylic tub with foam insulation under it instead of a mortar bed. I hated it. It squeeked and flexed. Maybe they do foam better nowadays but if I had to choose, I'd go with mortar.
Thank you,
Any recommandation on the mortar I should use?
John
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Old 02-18-2015, 12:37 AM   #13
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Subfloor levelling question


Some tubs have their own reinforced bottom and doesn't require mortar, it basically lays flat.
On the link you posted it states 2 different methods, one mortar, and one has feet/base and requires adhesive.
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Old 02-18-2015, 08:27 AM   #14
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Subfloor levelling question


if it comes with insulating pad, then a baseball size of insulating foam (maybe 1-2 of them) under the pad before setting tub, will keep things tight and quiet.

if you use mortar just get a thinset that is "flexible".

if it doesnt come with insulating pad then i would glue a piece of 1" rigid foam to tub, then set with spray foam or mortar.

if the tub has a pad and it sits about flush with floor, use spray foam, but use golf ball sized spots, etc.

wall ledgers support the tub, etc. the bottom is for insulating and quietness, etc.
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Old 02-19-2015, 06:58 PM   #15
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Subfloor levelling question


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Originally Posted by Slashp View Post
Hi,

What kind of shim would you recommand (I need around 1/8in) that would be incompressible?

I can't find plywood this thin at Lowes or Home Depot
John
Any idea of what incompressible material I could use to make 3.5in x 4ft x 1/8th shims?

Regards,
John

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