Alvin's Bathroom Remodel [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-20-2008, 02:20 PM
First, let me say great forum...awesome group that i'm thankful can help me out (hopefully) along the way. :bow:

tiling our bathroom floor (tub surround later) and wanted to ask if you guys think i'm doing ok with the subfloor. The area is only ~35 sq ft, and the walking area only ~21.

For joists that are SYP or Douglas Fir, in good condition, 7.25 inches tall, 1.5 inches wide, 24 inches on center, and 8 feet long between supports, the deflection calculated is 0.176 inches.

This translates to a deflection of L / 545.

House built in '35, and the inspector said she couldn't find a variation of greater than 1/2 inch in 1600 sq ft of oak floors, so things sound pretty solid.

There's 1x8 diag planking, and was planning on adding 1/2 inch BC, as instructed by Ditra, which i will be using on the ply.

As the deflectometer says, i should be fine. my only concern is that i'm laying 18 inch tiles...are they that different than 12's, is the deflection data just as valid?

PS: can anyone recommend a place to order the ditra tape (i'm assuming i should use it on a bathroom floor), as HD didn't have any?

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02-20-2008, 03:27 PM
Alvin, there isn't any difference in the structural requirements for big tile, just flatness. You'll want no more variation than 1/8" out of plane in any 10 foot direction. This is to make it easier to set the tiles with little lippage.

Order on-line at

John Bridge
02-20-2008, 04:13 PM
Hi Alvin, :)

What Bob said. If the floor is pretty flat you're in good shape. :)

02-20-2008, 05:31 PM
Thanks guys, feel much better now.

So how necessary is banding the ditra together and/or at the walls for a bathroom floor? Does it make a difference in everyday use, or is it as implied in the Ditra manual for unplanned situations such as overflows, etc?

02-21-2008, 09:47 AM
Alvin, in a typical bathroom waterproofing the floor outside the shower including all the Ditra seams and floor-to-wall connections serves no practical purpose. You could spend a lot of unnecessary time and money doing that only to discover that during an unexpected flood, the water simply flows right through the doorways.


02-24-2008, 02:01 PM
I've pulled up all the luan and have patched the rotten areas with 3/4 ply, and now have a small problem. The ply is 23/32, and the planks are 3/4 (minimum, may be a 16th or so thicker being old lumber, like all my studs are). What's the best way to level, considering that i'm putting 18" tile down...putting 1/2 ply on this followed by Ditra.

PS: Can someone rename my thread to Alvin's bathroom remodel or the like? Thanks.

02-24-2008, 02:09 PM
Well, I would have recommended you use full-length shims on those joists before you installed the plywood, Alvin. Or sistered them to raise the tops enough to make you plywood level. Tough to add an eighth inch to the top of that sheet.

My opinion; worth price charged.

02-24-2008, 02:13 PM
Thanks CX

Guess i should add that the ply is not screwed down yet :tup2:

So is that the best way to go? what's easy to find that i can use to shim a 1/16?

02-25-2008, 09:06 AM
Didn't notice that it was only a sixteenth, Alvin. Only good shims I know of for that thickness are sheetrock shims. I would maybe take a chance on those if that's not a ground floor, but I generally prefer to scab on some boards to level/flatten anything on a subfloor. Gonna be pretty easy in your situation.

My opinion; worth price charged.

02-25-2008, 09:33 AM
Heres an easy way:

Just go get some 15# felt roofing paper,
cut it into strips to lay on top of the joists,
experiment,, make a small test piece of the 3/4" ply,

use 1 layer,,maybe 2 layers of strips, that ought to bring you up 1/16"., tack it down with staples, then just refasten down your 3/4" ply.
make sure your 1x8 sheathing boards are tightly secured down as well before you test your height variances.

:) :) :)

02-29-2008, 04:30 PM
Got the subfloor down and within 1/8 for the entire bathroom.

Now on to the toilet. I have a 4" CI drain with a lead flange, lead was torn, so need to get it out. Bought one the Oatey expansion flanges that will seal up in the CI, but first I need to get that inner collar out...any best way(s) to get that loose/break it up?

my drain and the oatey expansion flange:

03-01-2008, 02:18 PM

03-01-2008, 04:10 PM
Typically, a plumber would fire up a MAPP gas torch, heat up that lead and scrape the softened lead down the the top edge of the CI.

You can't do that cause of the wooden floor structure and the risk of fire,

I would simply use a old sharp wood chisel,(when it goes dull on you, just put the edge to a grinder and resharpen it) and keep skimming off thin layers of the lead, lil by lil till your down to the edge of the CI,
looks to me like about an hours worth of hammering and chiseling..
Stuff an old towel down the CI to prevent lead pieces and tools from falling in, and sewer gas from coming up outta that pipe.

Plumbers carry a few old chisels for just such things.
I can't quite tell from the photo, but do you believe you have enough surface of that plywood to have a place to anchor your toilet flange screws into?

hope that helps??

Good luck! :) :) :)

03-04-2008, 03:14 PM
Thanks Maack, it's done and sealed.

Layout question. I will have 4 tiles and a 7 inch left over (18 inch tiles) b/w the tub and door. I can obviously shift and have two 12 1/2 inch tiles, one by tub, one by door. Is this the right choice bar none? The tile will be about 1/4 higher than the oak in the hall, so i will have a reducer of some kind at the doorway...just don't know if it will be covering the edge of the tile or not (prefer not, just butting up against it).

Any recommendations?

03-04-2008, 03:44 PM
It is always correct to have no cut smaller than one half of a full tile, Alvin. If that doesn't "look" right, do it differently. But that's the industry standard.

I always make my reducers from tile to wood such that they butt up to (but with appropriate gap) the tile and are flush with the top.

My opinion; worth price charged.

03-06-2008, 01:40 PM
1) Searched around and couldn't find answers to this ditra question...As it happens, my bathroom length is about 1/2inch short of exactly 2 widths of ditra. the 3 pitchers are of each seam w/o moving anything, the tub one, the middle one, and the door transition one (and yes, i'll be trimming some oak to create the appropriate expansion b/w the ply and oak :) ). Does the ditra need to go up to the perimeter, or can it be gapped from such same as the tile will? Can i leave a teeny gap b/w ditra sheets (i'm tentatively guessing no on this, as having a gap will defeat the purpose of decoupling, as the gap won't be decoupled)? How should i handle this? If i need more ditra, should i cut some off to avoid having to make a tedious < 1/2 inch sliver?

2) I've read all about perimeter joints in John's book, the liberry, Ditra manual, and am still a bit unsure of what to do. at the tub and door, can i simply leave 1/4" and just caulk? what about a 'foam' type deal in there i've read about? At the walls, can the tile just 'end', naked-like with a gap at studs since i'm covering with base?

Thanks in advance compadres!

03-07-2008, 08:16 AM
As it happens, my bathroom length is about 1/2inch short of exactly 2 widths of ditra............Does the ditra need to go up to the perimeter, or can it be gapped from such same as the tile will? Doesn't compute for moi. If your bath floor is smaller than two sheets of Ditra, cut one of the sheets to fit, leaving a small (1/4") gap at the perimeter.

But it looks like your bath floor is actually larger than two sheets of Ditra. In which case you already have your gap at the perimeter. I wouldn't leave any gaps between the Ditra sheets, just at the perimeter.

If I'm completely missing the question, it ain't the first time. :)

2. If the gap will be covered by trim, leave it; if it will be exposed, caulk it.

My opinion; worth price charged.

06-20-2008, 03:39 PM
I've long finished the floor now, and am procrastinating the tub surround, mostly due to worrying about doing the window properly.

It's a large old window that is very low and will get sprayed often. I have decided to use one solid pane of insulated glass that will be immobile (glued/caulded in). So I need some help with what to do with the kerdi around the window. I have downloaded John's book, and still have a few questions that either aren't clear or i missed.

1) Sill slope: the following photo is what i came up with to fix the sill slope and to ensure no water gets into the wall. Is is overkill?? should i not run the kerdi under the window pane? This would be kerdi first, window 2nd, which i could see being a problem. I guess i should just kerdi over the sloping block and turn it up onto the glass 1/4" like the book says...i assume thinset will adhere to glass just fine.

2) how do i kerdi the 2 bottom corners of the window...i see the inside and outside corner pieces, but neither are the shape of such a corner. does one of these two work for a window/nook corner with manipulation? NEVERMIND, just saw it, the inside corner as shown above flipped over fits these spots, correct?

3) for the 2 inside corners of the tub surround, should i use kerdi band (as opposed to wrapping kerdi through the corner all the way around)

4) At the back end of the tub (opposite end of the shower head), do i need to go as high as the shower head? I only ask, b/c the 54 sq ft roll from tile experts will only give me enough to go 1-2 feet short of the shower head height. I don't see water getting above that...but if you guys think i should go higher, i will order some extra.

5) is it ok for the rock to be up to 1/4" proud of the tub lip?

Thanks for all the help!

06-20-2008, 05:46 PM
Yes you need to go above the shower head.You can make little butterly pieces of Kerdi for corners like that or buy them.I think your idea for the window is fine, but i am a little confused,maybe Kerdi to the winow and silicone the joint there,or use their Kerdi fix.

10-25-2008, 02:28 PM
Ready to Kerdi now, just have a few things i'm still unsure about after reading John's book.

1) Can someone explain in detail the best way to attach the Kerdi to the window, and how much do i overlap onto the glass. my window is a single immovable solid pane of glass that basically is a large niche with a glass back wall (the window in the above photo is gone, replaced by all glass). Do i use caulk anywhere at the kerdi/glass transition?

2) Which is better to put up first for inside corners, the kerdi peices on the wall or the kerdi-band in the corner?

3) I also am still not sure of how to handle the pipes with Kerdi...tub handles, faucet, shower head...Just think i need a brief primer on waterproofing these locations.

Thanks in advance!

10-30-2008, 10:06 AM

I'd really appreciate it if someone could help me out. It's the last info i need and i'd really like to not have to wing it.

Thanks again

12-18-2008, 10:10 AM
I'll give it one more go to see if anyone would like to help out, otherwise i'll just wing it tomorrow.

thanks again

12-18-2008, 10:33 AM
Winging it is what the pros do, Alvin. :D

When you're not getting timely response to your questions, make another post and bump your thread to the top of the queue for attention. Sometimes our highly unpaid staff gets busy and posts drop to the bottom of the page or onto page 2 and get overlooked. But we don't mean to. :)

I see a photo of a framed window unit, but you described Kerdiing to a fixed pane of glass. Which you really got?

Generally if you actually needed to waterproof a piece of glass directly embedded in a wall corner or such, you'd fold your Kerdi or Kerdi Band onto the glass such that it would be covered by your tile installation. That small flap should be attached with Kerdi Fix. It's rather a PITA to do, but with care you can do it effectively.

2. Dealer's choice.

3. Generally you should have sealed the edges of the sheetrock at the penetrations with Kerdi Fix or Silicone early on. There is usually no need to actually seal around whatever is coming through the holes as there would be and escutcheon or some trim piece over it that would be sealed. If you need to seal around there, cut your Kerdi so it fits very close to the fixture and seal the small gap with Kerdi Fix. Schluter makes special pieces to seal around pipes, but I've never use one nor felt the need to have such.

My opinion; worth price charged.

12-18-2008, 10:58 AM
Thank you so much cx. I've bumped it a few times, but i know youz guyz don't get paid much for helping, so no worries.

here is a is a fixed piece of glass, essentially a giant niche with glass back. my concern is that small flap that will attach to the glass. this window is very low, and water will almost definitely be splashing directly onto the shelf you see.

Do i need kerdi fix for sure or is there another product i can use? (i'm in a town of about 4k people and would have to order it, and i will if that's by far the best way to go)

whatever is use, i'll thinset to the shelf just short of the glass, then kerdi fix the flap? should i silicone the top edge of the kerdi or not necessary?

ps: so i should seal the holes in the backerboard at the pipes before kerdi-ing?

pps: can you shower in a kerdi-ed shower without tile (just a curious question)

12-18-2008, 11:14 AM
I wouldn't use anything but Kerdi Fix in a critical area like that, Alvin. I recently completed a shower where I had to seal against the aluminum frame around a window four feet wide and only two feet above the shower floor. Gonna get major wet. Had only about 3/8ths" max contact with the window to allow the flap to be hidden behind the tile. Not fun.

And I don't ever recommend using caulking as the only line of defense in a waterproofing situation, but sometimes a guy gotta do what a guy gotta do, eh?

In your case there I would recommend you use Kerdi Fix to caulk the gap between the CBU and the glass before you start installing the Kerdi. Then attach the Kerdi flap to the glass with the Kerdi Fix. Best you're gonna be able to do, I think.

I'd recommend you order your Kerdi Fix from our friends at Tile ( You'll not get it any quicker unless you find a local source - which ain't likely. Tell David Taylor there we sent you. :)

Stuff's god-awful expensive at 20+ dollars a tube, but it's moderately wonderful stuff. I assure you we're workin' on Herr Schluter to try to get the price down on that pookey. :shades:

My opinion; worth price charged.