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Unread 11-19-2021, 12:01 AM   #1
JayTee
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Gutting & Tiling Bathroom Project

Been lurking for while during my bathroom remodel. Really appreciate all the info here.

Just finished the rough work and just discovered I have a layout issue.

My shower is at the far end of the bathroom and is 41" X 75" and has three walls. The controls are on one of the short walls which also has a 4" ledge at about 42 inches.

I am using (or want to use) 12 X 24 tiles horizontally for the shower walls. The two short walls work perfectly as the 12 X 24 tiles with a 50% offset work perfectly to 48" (about 7" beyond the shower glass).

The 75" wall is an issue. I cant seem to figure out a layout/offset that doesn't end up with a small piece at the end of a row. My first thought was 50% offset which left me about a 3 inch piece at the end of every other row. 33% offset was a bit better as eventually I end up with a row with that same 3" piece every three rows. The walls are 96" so I would end up with 3 rows with a short piece.

It would appear that mathematically, I can't escape this issue.

Any input/advice would be greatly appreciated.

Thanks.

JT
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Unread 11-19-2021, 11:52 AM   #2
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make sure your tile is flat enough to use a 50% offset
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Unread 11-19-2021, 12:05 PM   #3
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I can go any offset necessary to avoid short pieces.
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Unread 11-19-2021, 12:54 PM   #4
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Here are some ideas to consider, some/most of these may be bad ideas or ideas you have already considered and discarded for your situation:

- consider the tile sizing between adjacent pieces across the corner and whether the two corners will have similar 'looks' with the tile sizes in each corner (if someone might look at both corners at once and compare the two).
- consider vertical stack instead of horizontal
- consider zero offset
- consider shortening the wall
- draw out the shower and lines on paper for different scenarios you're comparing for better perspective. I did this for my shower and 'unfolded' the corners onto the flat paper without trying to do isometric/angles which would be too much work)
-consider floor tile grout lines interaction with wall tile grout lines (this probably would not be an issue)
-consider niche placement (if any)
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Unread 11-20-2021, 09:55 AM   #5
JayTee
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Phil - Thanks for the input. I had thought of some of those, but not all.

Shortening the wall is something I didnt think of but that would likely create other issues which are unknown. I think I'm leaning towards a 33% offset at this point. The floor tile is the same as the wall tile so I prefer to have the offsets match. I originally was thinking 50% but that gives me a short piece at the end of every row, where 33% gives me a short piece every three rows.

I will sketch out the lines today and see how the different scenarios look. Any opionion on if I should wrap the tile around the corners? For example, if I am suing 12 X 24 and end up with 3" piece at a corner, should the connecting piece on the other wall be 21"?

JT
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Unread 11-20-2021, 10:50 AM   #6
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Floor Prep Question

New to posting here and genuinely appreciate the wealth of information here. I have what I hope is a simple question which I found other threads have asked but didn't find a clear applicable answer as it appears this is a case-by-case question.

I am remodeling my bathroom which is on the 2nd floor. House was built in late 1980s. Plan on using 12X18 porcelain tiles on the floor and shower walls. Using smaller 2" mosaic for the shower floor. Shower system is presloped Laticrete pan/Hydroban.

Previous bathroom floor and walls were tiled with 4X4s. The tile was laid directly on the 3/4" T&G floor with a thick (1/2"+) mortar bed. The tile came up relatively easy and left no residue on the 3/4" T&G. I believe there was a thin layer of paper between the mortar and 3/4" T&G. There was no cracking or issues with the old tile. There was one small spot on the wall studs in the shower where it appears to have leaked.

3/4" T&G plywood subfloor on 2X12 joists on 16" centers. I did have to cut out the subfloor in a couple spots to relocate the toilet drain and relocate the old tub drain and vent to accommodate the new shower pan. The cuts spanned no more than 3 joists and I made the cuts down the center of the joists. I added additional support to the exposed joists where the floor was cut out. I don’t think this was necessary but I tend to err on the side of overkill.

I ran the Deflectolator and the results were L 1626 0.066. There are two major support beams running under the bathroom floor so the spans are short for the joist size. This would lead me to believe my floor is adequate for tiling. I was planning on putting 3/8" CDX plywood down as an underlayment and covering that with Laticrete Stratamat.

Is this overkill? Do I need the 3/8" CDX AND the stratamat. I've never used a decoupling membrane before. I understand the purpose of the decoupling membrane but wonder if I need the 3/8" CDX too.

Thanks

JT
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Unread 11-20-2021, 12:10 PM   #7
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Welcome, JT.

Is this the same bathroom as your previous thread about a shower with 12x24-inch wall tiles, or you got more than one bathroom project in progress?
Quote:
Originally Posted by JT
Previous bathroom floor....The tile was laid directly on the 3/4" T&G floor with a thick (1/2"+) mortar bed.

3/4" T&G plywood subfloor on 2X12 joists on 16" centers.
'Fraid I'm a bit confused here. You had a mortar bed over a 3/4" plywood subfloor, or you had a mortar bed over a 3/4" sawn board subfloor that you replaced with a plywood subfloor? Let's start there.

But in no case do you want to use a CD grade plywood over whatever you've got.

And you never "need" an uncoupling membrane, but you could use one in your application if you want.

My opinion; worth price charged.
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Unread 11-20-2021, 01:24 PM   #8
JayTee
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Yes, same project. My apologies if this was in error. Let me know the correct procedure for this.

The house was constructed with 3/4" T&G plywood over the 2X12 joists. The old tile I removed was installed over a mortar bed directly on top of the 3/4" plywood subfloor. Perhaps not directly since there appeared to be a thin paper-like material between the mortar and subfloor which is why there is no mortar on the subfloor now.

I did remove a couple small sections of the 3/4" subfloor to relocate drains. I replaced it with 3/4" CDX which after reading your response may have been in error.

Some additional information. In my conversations with the Laticrete tech people, I plan on applying Hydroban liquid to the entire wood subsurface prior to installing the Stratamat (if I still install the Stratamat).

You stated I shouldn't use CD plywood for anything on the floor. I am using CDX. Is it the C&D that is an issue or just plywood in general.

Thanks

JT
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Last edited by JayTee; 11-20-2021 at 01:48 PM.
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Unread 11-20-2021, 02:39 PM   #9
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Please keep all your project questions on this thread so folks can see what you're working on and what's been previously asked and answered, JT. A moderator can give it a more generic title any time you'd like to suggest one.

It's the D that's the problem. The CD grade plywood permits of large voids in both the face ply and the interior plies, which can result in soft spots that are not good for a ceramic tile installation. Given that and the patches, I'd recommend a second layer of nominal 1/2" exterior glue plywood with no face of grade lower than C.

I'm at a loss as to why you'd use Hydroban liquid over your plywood prior to installing Stratamat. What's the thinking there?

My opinion; worth price charged.
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Unread 11-20-2021, 02:53 PM   #10
JayTee
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Understood. Can you change the Thread Title to "Gutting & tiling bathroom project"?

I will get some ACX plywood as I've never seen BCX.

The thinking for the hydroban on the floor came from me wanting to extend the waterproofing out 1 or 2 feet from the edge of the shower. At that point I was half way across the bathroom so i figured why not keep going. Again, I tend to err on the side of overkill. Is there any downside to this?

In regard to the Stratamat, what is your thinking on why I dont need it? Is it that Im not on concrete and am on a very stable floor? When do you use a decoupling membrane?

Thanks again.

JT
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Unread 11-20-2021, 03:06 PM   #11
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My thinking on needing an uncoupling membrane has nothing at all to do with your particular application. You do need some sort of tile-friendly substrate over your plywood (well, actually you can get by with just two layers of plywood, but we (TYW) don't recommend it), but there are several types from which to choose and many brands among those types.

Keep in mind that there is no industry standard for uncoupling membranes and some of them can be made waterpoof, if that's your goal. You can also consider the liquid-applied membrane your substrate if the manufacturer indicates that. Wouldn't be my first choice, but that's personal preference.

Other than time and expense, I don't know that there is any downside to using both the Laticrete liquid-applied membrane and their uncoupling membrane if the manufacturer approves that. If a verbal confirmation from a company rep of that combatibility is enough for your comfort level, go for it.

Home centers in my area commonly carry a BC grade plywood.

My opinion; worth price charged.
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Unread 11-20-2021, 03:35 PM   #12
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All my correspondence with Laticrete has been via email. They make sure to tell you that their opinion is just that and in no way provides any assurances.

I'm unclear on the substrate. If I have a 3/4" subfloor and place 1/2" BCX on top of it, is that an adequate substrate for setting tile on?

Thanks

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Unread 11-20-2021, 06:12 PM   #13
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Any manufacturer of tile substrate products would accept your initial nominal 3/4" subfloor alone over 16" joist centers to be adequate. The ceramic tile industry does have an accepted method (F150) for installing your tiles directly to the second layer of plywood, which then becomes an underlayment, if it is installed correctly, including the face grain orientation, fastening only to the first layer of subflooring and not the joists, and the required 1/8th" gap between sheets, to name a few.

You must use a bonding mortar meeting ANSI A118.11 and it is commonly recommended that an A118.15 mortar be used.

You'll also have the problem of getting the substrate flat enough to accommodate your chosen tile size, which is not an easy thing with the plywood bonding surface.

But it can be done.

My opinion; worth price charged.
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Unread 11-20-2021, 07:12 PM   #14
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Thanks again.

The product I'm using to set my tile "Exceeds ANSI ANSI A118.15 HET, A118.4 and A118.11". Its a Laticrete product.

In regard to the 1/8" gap, I was planning on doing this but from what I've read that gap is for expansion. If the underlayment is subject to expansion, wouldn't that be a reason to use a decoupling membrane? I would imagine tile is set directly on anything that is going to expand, its going to either crack the grout or the tile. Something has to give. Not making an argument for the Stratamat. Just trying to understand the mechanics.

JT
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Unread 11-20-2021, 07:44 PM   #15
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Perfectly acceptable to name names here, JT, which Laticrete mortar are you using?

The primary purpose of any tile installation substrate is to separate the tile from the subfloor or other backing material as you suggest. While you can technically tile directly to the second layer of plywood, it is not the most tile friendly substrate and I'd recommend something better, which could include your StrataMat or the liquid-applied membrane, or both.

Lotsa choices. All up to you.

My opinion; worth price charged.
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