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CommanderCut 09-15-2020 02:32 PM

Bathroom Renovation Questions
5 Attachment(s)
Good day!

I am a first time DIY'er. I am running into several problems and am looking for help. My wife likes to "shoot first, ask questions later," meaning that sometimes things get done/purchased quickly, but without as much forethought as I would like. I am the opposite, and I get paralyzed trying to research the perfect solution to every problem, then don't get anything done... What a team!

So here I have my tub (Bootz Aloha, porcelain on steel) installed, and although it was a very tight squeeze getting it in there, it seems that I needed a couple of shims once I went to screw in the washers to hold the tub in place. Unfortunately, this makes the whole assembly a bit thick and now the walls have this "bolster" at the level of the tub flange, meaning the concrete board won't hang right (I think).

Attachment 215350
Attachment 215351

I want to install the hardie board down to 1/4" above the top of the tub flange. But the shims/washer get in the way of installing the concrete board, leaving a huge gap between the tub flange and concrete board (see schematic 1). So that doesn't work.

Attachment 215352

If I go over the shims with the concrete board, I am concerned that my shim-job+washers (0.47" thick) will make the concrete board lean out too far from the wall, causing the concrete board to not be vertical for the incoming tile job AND not line up with the drywall nicely on the non-drain end (see schematic 2). Perhaps I over-shimmed and can take one out on the ones with two shims. But is it ok for the concrete board from stud to tub to not be perfectly vertical? Even one shim will cause it to lean slightly, right?

Attachment 215353

Is the only solution to add furring strips to the walls (from tub to ceiling) so that the concrete board remains vertical and goes OVER the shims/washers (schematic 3)? This will again cause the concrete board to not be flush with the drywall on the right side of the tub near the window, but I read in another post that can be fixed with pencil tile trim.

Attachment 215355

Bootz online install instructions don't recommend drilling the holes through the tub, which could avoid the entire problem by hiding the shims at/below the tub flange, but that doesn't seem an option either.

So my questions are:
1)does the concrete board need to be perfectly vertical when installing or is a slight bow permitted?
2) But more importantly: Am I best served by furring out the studs on the two short ends of the tub and installing the concrete on those? Or is there a better solution that is obvious and I haven't seen yet.

FWIW, my wife purchased 20"x20" porcelain tiles for the floors/walls. She has a bucket of redguard and a couple of mesh tapes, so I assume that is how she is planning on waterproofing. I am sure that I will have (many) more questions then!

Thanks in advance for anyone willing to help! We have our work cut out for us...

cx 09-15-2020 03:45 PM

Welcome, Pete. :)

1. Yes. No.

2. Yes. Not really.

Schematic #3 is really what you want to do, except you want the CBU to continue down over the flange to within 1/8th" to 1/4" from the tub. And while shimming you want to make the studs as perfectly plumb and in-plane as you possibly can. You're gonna want a very, very, very flat substrate for those large format tiles. I recommend rips of plywood of the correct thickness(es) for such shimming.

It is difficult to properly waterproof the joint between wall and tub where the flange ends near the front. The tile industry has long encouraged the tub manufacturers to do better, but you see the result in what you've purchased.

It's possible to do a fair job using an appropriate fabric with a liquid-applied waterproofing membrane, but much care is needed to make that work.

Do be sure you extend your CBU walls three inches or so beyond the front of the tub for your tiled "tub leg" and be sure Mrs. Pete continues her waterproofing over that area. That's usually the first point of failure of such installations.

My opinion; worth price charged.

Tiger Mountain Tile Inc 09-15-2020 08:31 PM

Can you shove the tub all the way over to the window wall on the right? If so, you might have a fighting chance at getting that wall to flush out with the drywall.

For the other two walls, at least, you should fur out the studs so the come out past the tub, and vertical, and flat. You should put a straight edge on the studs to make sure they are flat with each other. No bulges or dips.

Also, it looks like you have a seam in the middle of a stud bay? If so, that's not good.

CommanderCut 09-15-2020 09:21 PM

3 Attachment(s)
Thank you for the prompt reply, CX and Mr. Upton. I really appreciate the advice. I made my way off to the hardware store to get some plywood. My neighbor has a planar and a table saw, so I can cut them to the appropriate thicknesses for furring out the wall I think.

I did as you suggested, Mr. Upton, and pushed the tub all the way to the right, which is the exterior wall. I probably did over-shim it a little bit on the first go around, but I managed to avoid having to use shims on that wall this time around.

As for the studs - I don't know what is normal, but these seem a bit... off. There was one missing in the middle - I think the prior builders planned on putting a niche in there, then gave up on it and just left the stud out. There were dangling nails where it should have been <shrug>. So I put a new stud in. It's not perfect - this being my first attempt, and it comes out maybe 1/8" more than the others. Should I replace this and try again? The other studs in the back are far from flat - some have dips - particularly the ones at the corners along the long edge. Not huge dips - but I did place a single shim there. I did not know that I couldn't put a seam there (in the stud bay), so I will take those down and fix that. Thanks for the tip!

Of course, because I pushed the tub towards the back of the tub, the gap on the front of the tub is now larger, up to 0.71" on one of the studs. But no problem - I will add the plywood furring as you suggested.

CX - you said 3" tub leg. On the exterior wall side - there is a window, and I have removed the drywall up to the vertical edge of the window. No idea what I am doing, but that seemed like a good place to stop (for aesthetic reasons, I suppose). It is only 2.15" from tub edge to that imaginary vertical line (that follows the edge of the window). Should I continue this to 3"?

Attachment 215361
Attachment 215359

The other side is up against a wall with a drywall corner (removed due to rust damage) and is 3.22" - so that side should be ok, I guess?

Attachment 215360

So, over the next few days, I will:
1) take down all the hardibacker that I incorrectly put up (all of it)
2) fur out the edges on the drain side of the tub.
3) stud replacement...?
4) Do more reading on how to waterproof that joint between the front tub flange and the wall. I see in your prior responses that you have answered this question numerous times. I will refer to your answers there.

For ease of your reponses, I numbered the questions here:
1) On the window side, should I continue the drywall removal up to 3" which will take it 0.85" around the window (over/under the window) to get a 3" tub leg on that side? Or should I stop at the imaginary line with the window where it is now (2.15")? I am happy to continue the demo to where it needs to go. Seems the only thing I'm decent at so far...

2) Should I be replacing all these studs? sigh...

Thanks for the quick responses and helpful advice. One step forward equals two steps back at the moment.

cx 09-15-2020 10:13 PM

1. I'd try to run my CBU and waterproofing right up to the window casing on that end, Pete, and make the tub leg width below the window the same width as the tub leg on the other end of the tub for symmetry. The lower portions (height of tub) are the most critical for waterproofing. That's where you usually start seeing paint blister and drywall soften when not properly waterproofed.

2. Can't say. What you've gotta do is bring the faces of all the studs into plane with one another. Planing, shimming, sistering, replacing, whatever it takes.

Keep in mind the tile industry recommendation for substrate flatness for tiles with any edge longer than 15 inches is no deviation from intended plane of more than 1/8th" in ten feet nor 1/16th" in two feet. And for those 20" tiles you'll be happy to have your substrate every bit as flat as that.

Numbering your questions makes life easier on this end. Thanks.

My opinion; worth price charged.

CommanderCut 09-16-2020 06:13 PM

Got it. Well, I have my work cut out for me. Work was busy today, but I will be back with an update Friday after I fix the studs!

I'll do as you said and bring the tub leg out to 3 inches on the bottom on the window side.

Thanks for the advice.

ss3964spd 09-18-2020 06:25 AM

After you moved the tub all the way to one end to close that gap, does your tub drain still line up, Pete? If not, are you able to access it from underneath to move it?

Also, you closed the gap at one end, but opened it at the other. How wide is it now?

CommanderCut 09-18-2020 02:01 PM

The tub drain is one of those adjustable do-hickeys from the big box store, so I think that will be alright. I have access to the tub drain from behind that wall on the left through the closet there to make adjustments.

The gap on the left/drain side of the tub is now 0.71" on the most inside stud and 0.44" on the stud closest to the outside of the tub. I am sure this will change again with the upcoming stud-work I am about to do.

I have had a busy couple of days at work, so haven't gotten anything done in a couple of days. But tonight, I am planning on pulling the tub back out and checking all of these old studs to make sure they are in a plane, especially because of the large format tiles my wife purchased. I know that at least the stud that I placed isn't, so I will need to take the stringer down again and fix that at the very least. I anticipate having to probably fix several of them, as CX suggested.

My wife did offer to purchase a smaller format tile for the walls, and we might pursue that route. We haven't decided on that yet. Currently at this point, I am just trying to get the tub and concrete walls up.

I assume that the concrete boards are no good once you take the screws out, and cannot be used again. Is that correct?

cx 09-18-2020 02:11 PM

If you've not damaged your CBU other than some screw holes, Pete, I wouldn't hesitate to install them again. Put your fasteners somewhere other than the old holes, though.

My opinion; worth price charged.

jadnashua 09-18-2020 02:23 PM

What does the tub have on the bottom of it? When setting the tub, you want to ensure that the rim is level all the way around AND, unless the bottom of the tub has something applied to it already, you want to fill any gaps underneath it to ensure it is well supported. Otherwise, when standing in the tub, that porcelain on steel tub will flex, the finish will craze, and it will eventually start to rust.

Some people use some mortar mix placed in piles underneath the tub, then when setting it in place, carefully level it. The piles give it some room to spread out as you press the tub in place. It helps to put a layer of plastic underneath to help prevent the wood from sucking moisture out of your mortar.

Don't muck around in the tub until the mortar has an opportunity to cure - give it at least overnight.

Porcelain on steel tubs aren't known for their long-term durability...drop anything onto the surface, and you may crack the finish, letting water get to the steel beneath that will then rust.

CommanderCut 09-18-2020 02:39 PM

The tub. O the tub! It was a "shoot first, question later" purchase from my wife. Bootz Aloha, porcelain on steel. The bottom of the tub has a Styrofoam base.

I used Henry 549 to level the floor prior to installing the tub. I followed the youtube video here https://www.youtube.com/watch?v=RoB3ziqk0oI

He does the floor leveling at 6 min 25 seconds if you want to fast forward it. I decided to do it this way because I was afraid I would have to pull the tub out later to fix some mistake (which I have now officially made), so I didn't want to concrete it in place. I made the floor level in the areas where the Styrofoam base sits, and I think it actually came out alright. It is level and pretty flat and the tub drain fit well. The styrofoam base doesn't squeak or squeal (you know what I mean? like when it shifts?) when i stand in the different parts of the tub.

I have heard that the porcelain on steel tubs are really not great, and I wasn't terribly pleased when i read about what she had brought home, but I will work what is here I suppose. Is it worth eating the $155 (the cost of the Bootz Aloha) to get a new/different material tub? It may be a hard sell, as that tub is not returnable at this point.

jadnashua 09-18-2020 03:10 PM

The tub can last, but that is less likely if you're not really careful. Porcelain on cast iron works because the CI is really strong and stable. But, even that can get chipped if you drop something hard on it. Plumber's that I have talked with put that type of tub at the bottom of their list, with CI at the top, then maybe acrylic, or maybe Americast, then fiberglass, then porcelain on steel.

SOrt of depends on how long you plan to be there. A little chip in the paint around the drain or overflow can result in rust, as will damaging the finish anywhere else on it.

Tiger Mountain Tile Inc 09-19-2020 02:30 PM

For flattening your walls, you can use a planer to trim down the high spots and you can fur out the studs that are really far back and use these drywall shims to fine tune things.

You'll have to fur out the whole plumbing wall and then put corner metal on the outside of it.

One thing to keep in mind is that by furring out the plumbing wall your plumbing fixture is probably too far back in the wall now. I don't know if you were planning on changing that, or not. Some of them they make extensions for but not sure what you have.

CommanderCut 09-20-2020 01:01 AM

Got the planar and some furring strips! Giving it a go in the morning.

CommanderCut 09-24-2020 08:51 AM

5 Attachment(s)
Well, some more progress (hopefully forward progress this time).

Here is where I am at:

Using a planer mostly, and an oscillating multitool/sander for places the planer couldn't reach, I got all the studs in plane. Seems things aren't perfectly square with the alcove - the plumbing wall comes out toward the tub by 4 mm at the near corner of the tub, but not so at the ceiling I guess? The middle stud in the plumbing wall was much farther out than the other two due to some bowing, but i got it in plane with the other two studs as you can see in the pictures below. I used furring strips (2x1x8) to bring out that wall 0.75" which is just at the tub flange, slightly over it on the near side, maybe a mm. I still need to fix the tub to those strips there.

Attachment 215458Attachment 215459Attachment 215460

I also demo'd out the exterior wall to allow for 3" tub leg as CX recommended, installed two sheets of concrete board on the back wall, and had to get a q-tip shoved so far into my nose that it tickled my brain (COVID negative though, so that's a win).

While all this was going on - I discovered a few things. I think there is water damage around where the toilet was.

Attachment 215461Attachment 215462

And the handle that controls the water in the tub is leaking... slowly. Aaaand - as Mr. Upton suggested - with the furring strips and the CBU and the tile, it won't be long enough anyways - and if it's leaking, I'm thinking that it should be replaced. I was thinking about getting a new valve and changing out the plumbing to PEX.

My plan for the near future:
-Fix the plumbing, somehow. Still learning what to do there.
-Finish putting up concrete board, over the tub flange and down to the tub deck (1/4" above it), as per CX's suggestion
-Thinset/mesh tape over the seams
-Kerdiband/kerdifix or some other membrane waterproofing to cover 1/4" gap from tub to CBU and down the tub leg
-RedGuard it all

1) Any issues with what I've done that are glaringly horrible?
2) My wife bought the premixed thinset for the fiber tape/seams on the walls. I have read before this isn't any good, that it is just mastic with sand. Is that true? Looks like manufacturer's recommendation here on page 7 includes mastic? But modified thinset is better for the tape, right? Just looking for some guidance here.
3) This is water damage around the toilet, right?
4) Would you recommend removing and replacing that subfloor there?
5) Subfloor is plywood and measures 3/4". I should use 1/2" hardiebacker for the floor, correct?
6) Toilet flange is 0.75" above the plywood subfloor. Adding a 1/2" CBU on top of that leaves 0.25" before tiling. Would you leave this alone or replace it with something higher?

Thanks again to everyone in advance.

cx 09-24-2020 10:19 AM

1. Probably.

2. Tell us specifically what it is, but generally yes, it's probably an organic adhesive and not what you want for the application. Says somewhere on the container that it meets ANSI A136.1, yes?

3. Looks like.

4. Poke it with a screwdriver or similar tool and see if it's soft. If not, you can probably get by with it under a CBU.

5. Only if you need the extra height. If you're using Hardiebacker, read that installation instruction information you linked.

6. The only proper location for the WC drain flange is on top of the finished flooring. Whatever best accomplishes that in your situation is what I'd recommend you use. Keep in mind that the Hardiebacker 500 is not 1/2" thick. More like 7/16ths" thick.

If you can make your CBU plus thinset mortar bed plus tile plus bonding mortar thickness fit snugly under that flange you'll have what you really want.

My opinion; worth price charged.

CommanderCut 09-24-2020 02:20 PM

3 Attachment(s)
1. <...nervous laugh...>

2. Custom's SimpleSet Pre-mixed Thin-set Mortar. Exceeds A136.1 Type one.
Attachment 215464

3/4. Ummm, kinda soft... I stuck the screwdriver in as recommended and it sinks in a few mm and leaves a philips head sized mark, which you can see just adjacent to where the screwdriver is in the photo. Pushing just as hard on the clean surface doesn't leave any mark.
Attachment 215467Attachment 215466

5. 1/4" hardiebacker it is! I read somewhere that the total floor height needed to be 1-1/8" so I thought I needed the thicker hardiebacker to make up for it with the plywood subfloor measuring 3/4"

6. Got it!


cx 09-24-2020 03:51 PM

2. Not likely you could make a worse choice there, Pete. You do not want to involve yourself with anything from Homer's with a name starting with Simple. While Custom Building products makes some good tile installation materials, that is not one of them.

3/4. That's gonna be a judgement call, but your single layer subfloor is already less than I'd want for my ceramic tile installation, and an old, damaged, single layer plywood subfloor would make me even less comfortable. Yeah, it's under the terlit, but...... Entirely up to you.

5. There is no such requirement in the ceramic tile industry. There are specific requirements for subflooring called out for various industry published installation methods, and each manufacturer of tile installation substrates has his own published minimum requirements, but there is no overall thickness requirement.

My opinion; worth price charged.

CommanderCut 09-24-2020 04:18 PM

2. Understood. Will return and use non-premixed modified thinset.

3/4. I will replace the damaged subfloor.

5. Got it. Cool.

Working on fixing the plumbing today and tomorrow. Fixing subfloor water damage next.

ss3964spd 09-25-2020 07:19 AM

Pete, you'll want to replace as large a section of that compromised 3/4" ply as is practical. Meaning, you want to try to get it to span 3 joists if you can. You also want to make sure you have blocking under any unsupported edge.

Depot will have B/C grade exposure 1 plywood and that's what you want. You also want to orient the new ply so that it's long edge is perpendicular to the joists.

If you have access from below just cut out the old toilet drain. Doing so will make it easier to get the old ply out and waaaay easier to install the new ply. Added bonus is you can ensure the new flange rests atop your new tile.

CommanderCut 09-25-2020 07:31 AM

I was thinking about just replacing that entire panel, it’s not too much larger than the extent of the water damage itself.

Thanks for the advice about the plywood and how to replace it. That job is upcoming, probably Sunday or so.

No access from below unfortunately. Maybe time to purchase a reciprocating saw...??

ss3964spd 09-25-2020 07:48 AM

A rep saw will do the trick (love mine). Make sure you know there's nothing under there you could cut through, and keep the blade angle really low so you don't cut into a joist. A circular saw with the blade set to the thickness of the ply will also work in some spots.

CommanderCut 09-26-2020 01:38 AM

5 Attachment(s)
Plumbing question -
(if this is the wrong place to post this question, let me know. You all have been immensely helpful so far).

I got a new mixing valve to replace our old one that is sporadically leaking and off center from the new tub by 1/2". But there is a stud in the way and I am wondering what the best way to handle this is.

Here is a picture of the overall situation right now.

Attachment 215498Attachment 215499Attachment 215500

You can see that old valve is really close to the center stud there. That middle stud is 15.5 inches o.c. from the stud to the right.

My new valve, even when spaced over 1/2" to the right to center over the tub drain won't fit.

Attachment 215501Attachment 215502

The floor joists run along the same direction as the long edge of the bathtub, which means that this wall is perpendicular to them. So I am assuming this counts as load bearing. That middle stud (2x4) already has a 1" hole drilled into it. As the mixing valve will need to be pushed forward with that stud furred outward, I don't think I can drill another hole into it to compensate for the forward position of the mixing valve.

What do you think is the best option here?
-Add two studs, one to the left, one to the right, then remove the center stud, leaving a big stud bay in which to mount this? This would fix the problem of "old stud already has a hole that doesn't work for my setup."
-Different mixing valve? (doesn't fix the above problem)
-Something else I am not thinking of?

ss3964spd 09-26-2020 08:11 AM

No, Sir, that's not going to be a load bearing wall.

If this was mine, Pete, I'd simply demo that entire wall and rebuild it with the framing where you need it to be. Initially it appears that doing so creates more work but in the long run it could well be that it takes less time than trying to make what you have work.

Added bonus: You can clearly demonstrate to Mrs. Pete that the reciprocating saw purchase was absolutely necessary.

CommanderCut 10-03-2020 01:39 PM


You mentioned that my 3/4” plywood subfloor was “less than you would like” for laying tile.

If it does not create an uneven surface from the hallway (and it might, I’m not home at the moment) would you

1) recommend adding another 1/2” layer of plywood on top of the current subfloor?

2) Would that go underneath the tub as well or just areas where tile is going to go (up to the edge of the tub)?

cx 10-03-2020 03:19 PM

1. Yes. You currently meet the substrate manufacturer's requirement for subflooring, presuming your joists are on 16" centers, but you must remember that those recommendations are based upon testing with new material, in near perfect condition, near perfectly installed over joists with zero deflection and the test needs pass only once for the installed method to be accepted.

2. I wouldn't be concerned with under the tub, but if the tub were removed at the time I would certainly install the second layer of subflooring there, too. You'd want to pay close attention to the bottom of the profile of the front of the tub before raising the floor there and tiling to the tub.

My opinion; worth price charged.

CommanderCut 10-03-2020 05:52 PM

1 Attachment(s)
The hallway flooring sits 0.77" above the current plywood subfloor (which measures 0.73").

Attachment 215714

Adding on an additional 15/32" piece of plywood in the bathroom (actual measurement 0.47" thick) plus the hardiebacker (0.25") plus the thinset (?) and tile (5/16, but I measured it at 0.36" thick). So:

+ thinset thickness (for both the concrete board and tile)?
height of bathroom floor over current subfloor =1.08" + thinset thickness.

-0.77" height of hallway floor above current subfloor
Height of bathroom floor over hallway floor =0.31" + thinset thickness

In your experience, is this too much of a height increase going into a bathroom?

cx 10-03-2020 07:15 PM

Pete, you need to trade your dial caliper for a yardstick or steel tape or you're gonna set yourself up for disappointment come time to actually install those materials. :)

All your measurements are within the range of tolerances for the materials. The thinset mortar thickness is gonna depend upon your mortar and your trowel and your technique, but the actual industry requirement is that it be a minimum of 3/32nds" thick when the tile is fully set. You can add up all the numbers you've come up with and estimate what you might have for a step there, but until you actually install the various pieces, you're not really gonna know what you've got.

The 5/16ths" step you're predicting would be code compliant, but there are people (I would be an example) who could trip over it. Repeatedly! :D

Aside from that, and the possible aesthetic consideration of the raw tile edge, you could likely get by with your plan. Making some sort of threshold piece to match the heights might help the aesthetic part of that or you may like that even less.

My opinion; worth price charged.

CommanderCut 10-06-2020 07:00 PM

1 Attachment(s)

Pete, you need to trade your dial caliper for a yardstick or steel tape or you're gonna set yourself up for disappointment come time to actually install those materials.
Over my dead body! hahaha

I spoke with my wife and we agreed that the height difference isn't too terrible (between the hallway and the bathroom) and doing the second layer of plywood as you recommended needs to be done.

So I did some measuring with my 4' level and found the subfloor is pretty significantly crowned - highest in the middle and lowest on the edges - like a road - level along the long axis and low on the edges. Almost 1/2" lower in some places.

Attachment 215767


1) Is this 15/32" Plytanium plywood from Lowes sufficient? It is listed as "Exposure 1" and veneer grade is listed as "rated." I am not sure what that means in terms of grade.

2) Should I use a concrete floor leveling compound to level the floor or something else?

3) When do I level? Before I install the new 1/2" plywood? Or should I install the plywood and then level after that?

Houston Remodeler 10-06-2020 07:42 PM

1- No. This is sheathing and the manufacturer says it is not rated for floors. You need CC or better. ROund these parts BC is easier to find.

2- SLC = self leveling compound. If you are having height issues, the thinnest will be Liquid Backer Board by Ardex.

3- Yes, framing is always first in the line up.

jadnashua 10-06-2020 07:56 PM

I'm not sure how a 4-ply panel would resist warping properly...generally, you want something with an odd number of plies so the two outer ones are going the same way. This pre-stresses it to lay flat and provide the desired strength along that axis.

You want to ensure the panel doesn't have a D-face. The difference between Exterior glue and Exposure 1 is the duration of time it is expected to be able to resist moisture with exterior lasting longer than exposure 1 does. Normally, this isn't an issue inside. Moisture resistance for the glue is important as the extra moisture in thinset will be there for a few days before it either wicks away or evaporates (a little bit of both usually happens).

Most grade stamps I remember on ply indicate not only the glue rating, but also the quality of the plies...you don't want a D ply on your plywood's exterior surface but exposure 1 stuff could have one internally, so exterior rated tends to be better, since it will have at least a C-face as its lowest quality face both interior and exterior.

Now, unfortunately, that didn't clear up your question!

So, without examining the grade stamp, can't say whether it will be suitable.

cx 10-06-2020 08:45 PM

Jim, I can't recall the last time I saw nominal half-inch exterior glue plywood that had more than 4 plies. Seems to be the norm these days.

I agree with Jim that I'd wanna see a grade stamp to know what grade that Plytanium material is. Just because it says sheething in the advertisement does not necessarily rule it out for your application. I'm a bit skeptical, though, because an ad right next to it is for what appears to be the same material except it indicates it's sanded. Unfortunately, I don't find it as easy to identify that sort of engineered wood panels these days. Gimme a grade stamp instead of a fancy new name, say I.

My opinion; worth price charged.

jadnashua 10-06-2020 09:48 PM

Plywood usually has an odd number of plies, not sure how those with four would be oriented internally to gain max strength along the long axis. Anyway, a grade stamp should define things once it's properly decoded. The stuff used to be easier!

CommanderCut 10-06-2020 09:55 PM

I suppose you are probably referring to this:Plytanium Plywood which says it is rated as BCX, weather exposure "Exterior," and the checkbox is listed as "for use with floors."

I will go to the store tomorrow or Thursday afternoon to check out the stamp on that plywood linked above. If the stamp on the wood matches those specs (exterior and BC), I assume that is sufficient then?

Put down the new plywood, then the self leveling concrete on top of that. Got it! It's going to be a fun weekend...

CommanderCut 10-08-2020 02:51 PM

1 Attachment(s)
Well, my Lowe's trip to pick up 1/2" plywood for the layer on top of the subfloor was horrible. There was no 15/32" exterior, BCX plywood left that wasn't covered with tons of mold. This is what they forklifted down for me. I went through about 10 or 15 panels before I gave up. I understand that wood panels have mold, but this seemed a bit excessive. This wasn't the worst panel either.

Attachment 215786

So I had to get the next step up which was exterior, ACX (admittedly not a TON more expensive for a small room), but it is 5-ply and someone mentioned earlier that an odd number of ply's (plies?) was better. Unfortunately, today is the last day I have my wife's minivan to transport 4x8' pieces of wood from the store. Soooo, the wood isn't perfectly flat, but after looking at 30ish pieces of plywood at the Lowe's, none of them were very flat, so I picked the flattest ones I could find. :shrug: Oh yeah - and I learned that twine - even lots of twine - is inadequate for keeping your trunk lid tied down when carrying 4x8' plywood. Gotta get me a bungie cord... hahaha

I read the article on underlayment in the Liberry. I will:
-Place the panels so that the strength axis (longitudinal) is perpendicular to my joists - which is the same direction as the current subfloor plywood panels.
-I will place the plywood panels so that they are 24" off center from the long seam of the current subfloor panels.
-The plywood is 8' and the room is 8' wide (& 5'6" wide at the tub). So i guess the plywood will just span the width of the room, where it can.

If I stay exactly 24" off the subfloor panel edges, I will have about a 1' x 8' strip on the entrance side of the bathroom (the first seam is 3 feet in - if that makes sense) and about a 2' x 5'6" strip on the other side. Unfortunately, if I center the plywood boards this way, it also leaves a couple-inch wide strip in the back of the closet, which is 2' and a couple inches from the middle of the nearest visible seam.

So my question is:
1) is a 1 foot x 8 foot strip of plywood on the near side of the bathroom too thin? If so, what should I aim for? I can take some off the next plywood panel if this strip needs to be wider.
2) The plywood is a bit warped. I am sure it will flatten when I screw it down. Is that ok? I don't know if I can easily get any flat, non-moldy plywood that meets the specs listed previously in this thread. I have seemingly exhausted my options at the local big box stores.

As always, thanks for your help thus far.

ss3964spd 10-09-2020 05:54 AM

Some skanky looking plywood there, Pete, can't say that I've had that challenge with panels from the Depot that's a mile from me, and the BCX sheets I've bought have been pretty flat, too. Had I known you were going to be jamming those 4X8 sheets into the back of a minivan I'd have offered my pick up. Or, I'd have just gone to watch. :D

Regardless, the ACX sheets you picked up should be fine. When you go about fastening them down with appropriate screws try to work from the center of the panel out if they're not laying pretty flat.

While shooting for a 24" overlap of the underlying panels is ideal I wouldn't worry at all if I could achieve at least an 8 inch overlap, and didn't. If at all possible place any narrower pieces away from heavy traffic areas; under the vanities, in the closets, etc. If you need to adjust your overlap spacing to do that, I would.

CommanderCut 10-18-2020 05:39 PM

5 Attachment(s)
Alright, it's been a couple of days. Got some work done.

Attachment 215995
I have removed the toilet flange, removed the water-damaged plywood subfloor under the toilet, added a bunch of bolsters, and replaced the damaged floor there.

Attachment 215993
Then I added a 1/2" plywood to the existing 3/4" subfloor following the oft-cited directions in the Liberry article.

Attachment 215991
This is the old plumbing wall, with the obtrusive stud in the middle, which prevented me from adding my Delta MultiChoice R10000-UNWS.

Attachment 215994Attachment 215992
I replaced the stud in the middle with two on the sides, added furring strips, and got everything all in a plane and plumb (again). I did my math (god, I hope it's right) and added 2x4s between the studs at the calculated depth. I secured the multichoice valve and all the plumbing. Added some 1/4 turn ball valves to the plumbing access behind the tub. This was my first time doing soldering.

I am at the point (I think) where I need to level the floor. Originally, we were thinking about going with hardie backer on the floor, but after doing all the plywood which took me an entire weekend with my dad, we decided to go with an uncoupling membrane instead of the concrete fiberboard. The floor is crowned, high point in the center, and low around all the edges. So I was going to put the self leveler down before the uncoupling membrane.

Before, someone mentioned Ardex Backerboard, but that was before we were planning on using uncoupling membrane.

Does anyone have any recommendations for what is a good self leveling compound (for a novice) for before placing the uncoupling membrane on top of my plywood? I have access to Home Depot and Lowes. I've watched plenty of "failed SLC videos" on YouTube and so I am trying to avoid that.

Thanks again for your help so far.

CommanderCut 10-18-2020 10:57 PM

I realize in the previous post I said "level" the floor. I am just trying to make it flat for the uncoupling membrane. Not necessarily level.

CommanderCut 10-25-2020 04:42 PM

Gonna bump this thread.

Just a quick summary:
2 layers of plywood down (3/4" original subfloor and 1/2" nominal on top of that).
The floor is crowned, about 3/8" low on the left side and 5/16" low on the right side. Tile is 20"x20".

The plan:
-Self leveling compound on top of new plywood subfloor to flatten out floor
-Uncoupling membrane on top of that
-Tile on top of that.

I was having trouble figuring out which self-leveler to use. HD has Henry 542 Liquid Backerboard, 544, 555, 565.

From what I can tell:
-542 works on plywood or concrete floors, does not require metal lath
-544 is for concrete and terazzo floors. Not plywood.
-555 and 565 seem pretty identical, both require metal lath

So i was thinking about using Henry 542. Unfortunately, HD needs to special order it, and it won't be here for about a week. In the instructions it says, "if necessary, sand down to bare wood." And I have seen other online resources indicating that sanding is important or even necessary no matter what floor you have. I have brand new plywood. So, questions:

1) Would you sand the new plywood subfloor prior to priming?
2) Does this plan/product seem sound?

jadnashua 10-25-2020 06:40 PM

To ensure a good bond, if there's crud on it (say paint, drywall mud, adhesives, etc.), they want it clean of those contaminants. Otherwise, on new material, you should be okay, but I'd still call their tech support...seems like you'll have enough time to get an answer from those that designed it!

WRT any of these self-leveling cement products, they aren't like water...more like pancake batter and if you've ever made pancakes, the stuff doesn't spread to the edges of the pan. Even water on say a freshly waxed car, ends up with beads rather than sheeting off. That's an extreme example, but similar to what happens with slc. To get flat, it often needs some help. The issue with any of these is how much time do you have to achieve that otherwise, it's like trying to get a partially frozen puddle to lay flat again. It will try to have a meniscus (rounded edge) on it unless you spread it to break the surface tension. Best to measure out your water and have helpers, as to get a good result, you need to keep mixing, pouring, and maintain a wet edge. You'll need something to help spread it out, too. I don't know whether they recommend their porcupine roller to help break the surface tension or not; on some slc's, that can help immensely. I used a different Ardex product, and ended up using a snow rake to help move it around, as it had a long handle. The stuff will run anywhere there's a hole or gap, so watch that ,and you will want to use something like sill seal around the perimeter of the walls to provide a small resilient gap and help prevent it from running underneath the walls.

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