Wood SubFloor Flattening

[AZ Contractor]

See attachment.

Check your installation manual.

 

[Hdmstng]

My idea is to use some 1/4" plywood in the low areas followed up with some self leveling compound to flatten the floor. See the orange area. Then use some 1/2" cement board that extends underneath the tub to support the apron (the gray) that would go over the 1/4" plywood. I'd then need to adjust the stringer along the backwall up a bit to make sure everything was level. I'd then continue down with the cement board to cover the rest of the bathroom floor in preparation for the tile.

 

[Sponsor]

 

[hj]

tubs

I have installed too many tubs to count in the past 55+ years and I have always used a back ledger only and NEVER used concrete/ mortar under them.

 

[Frenchie]

Um... I just looked up the installation instructions for the American Standard Princeton. Near as I can tell, it doesn't say to use a mortar bed, but it doesn't say NOT to...

Also says to butt the cement board to the apron - not to extend it under the apron, like you have planned.


note: I couldn't attach it, too big. Here's a link to the download:

antlerproperties.com/rehab02/bath/Install Americast Tub.pdf


???

 

[Hdmstng]

Um... I just looked up the installation instructions for the American Standard Princeton. Near as I can tell, it doesn't say to use a mortar bed, but it doesn't say NOT to...

Also says to butt the cement board to the apron - not to extend it under the apron, like you have planned.


note: I couldn't attach it, too big. Here's a link to the download:

antlerproperties.com/rehab02/bath/Install Americast Tub.pdf


???

The instructions you linked to are very close to the ones I have that came with the tub, but aren't identical. Mine don't talk about running the cement board to the apron but it does spell out not to use any sort of bedding under the tub. It's the same as what AZ Contractor posted.

I have a couple of pieces of melamine and/or MDF board that is 1/8" and 1/4" thick. They seem to be a perfect fit for raising and leveling the floor to set the tub apron on. Is there any drawback to using it or should I find a different material?

Also just wanted to say thanks for all the input and help!

 

[Frenchie]

I have a couple of pieces of melamine and/or MDF board that is 1/8" and 1/4" thick. They seem to be a perfect fit for raising and leveling the floor to set the tub apron on. Is there any drawback to using it or should I find a different material?

Yes. Either of those will fall apart if it ever gets wet, or even damp. I'd want something reasonably rot-proof, like exterior ply or cedar or even just a regular doug fir 2x4' cut down... I think floor leveler was the best plan I've heard.

Almost anything is better than mdf.

 

[AZ Contractor]

Yes. Either of those will fall apart if it ever gets wet, or even damp. I'd want something reasonably rot-proof, like exterior ply or cedar or even just a regular doug fir 2x4' cut down... I think floor leveler was the best plan I've heard.

Almost anything is better than mdf.

Don't you think the floor leveler will break into pieces being only 1/8" to 1/4" with the minor flexing of the sub-floor?

I agree with the "no mdf".

 

[Statjunk]

Don't you think the floor leveler will break into pieces being only 1/8" to 1/4" with the minor flexing of the sub-floor?

I agree with the "no mdf".

I would think so!

I wonder why the don't want you using a mortor bed. Could it be that they are building such crappy tubs that they have high warranty claims so they want the option of easy removal?

I just installed an American Standard Jacuzzi tub and I've already had two warranty repairs in less than 6 months.

Tom

 

[AZ Contractor]

I would think so!

I wonder why the don't want you using a mortor bed. Could it be that they are building such crappy tubs that they have high warranty claims so they want the option of easy removal?

I just installed an American Standard Jacuzzi tub and I've already had two warranty repairs in less than 6 months.

Tom

I'm not sure either.

Could be possible that there is a chemical reaction with the alkalies in the mortar and the tub causing premature tub fatigue?

 

[Mikey]

How about a bed of glass beads?

 

[Jadnashua]

The simple addition of a sheet of plastic between the mortar and the tub would isolate it and still provide the desired leveling and support. There's no real reason to actually adhere the thing in place with this, just to provide good support. On a tub that can flex, adding support will make it last longer. Fatigue cracks don't happen unless the material is stressed by deflection repeatedly. You're also less likely to loosen or break the drain. It could take numerous years, but it will make a difference in the long run. Personally, I don't like a tub that flexes when I stand there taking a shower, and my original fiberglass one exhibited numerous stress cracks because it was not well supported, even though it had numerous reinforcement ribs that actually sat on the floor.