Drywall to Backerboard transition in tiled showers

by Roger

drywall, backerboard transitionWhen you tear out and rebuild your shower walls you are left with a transition between the old, existing drywall and the new stuff – cement backerboard or drywall (if you’re using kerdi). Whaddya do with it? And how do you do it? And why am I the one asking questions – that seems backwards.

If at all possible, when you remove the old stuff you want to cut a straight line down the drywall to make for a clean transition. If it isn’t straight or was simply torn out without any regards to actually rebuilding it, then find a spot where you can cut a straight line from top to bottom. You want to have a level line for your transition.

So before you begin you want something similar to that horrible graphic right there I just created with a bottle of scotch and my toes. The left side is looking into the wall cavity with one stud, that big brown looking thing? Yeah, it’s supposed to be a wall stud. You are not allowed to give me crap about my lack of Photoshop skills!

drywall, backerboard transitionWhat we need is a way to shore out the new substrate (backerboard) to be solid and on an even plane with the existing stuff. We have a very, very specialized item for this. Listen carefully, because it’s a deeply guarded secret. Ready?

It’s a  2×4.

Take a 2×4 and cut it to the length of either the entire wall or simply from about six inches from the top to six inches below the bottom. The latter is often the only way to do it – you still need to be able to get it into the wall cavity over the tub and around the other studs. It needs to fit in there.

Just take the 2×4 and get it into the wall. Turn it so that the width (3 1/2″) is split between the open space and the existing drywall. There will be 1 3/4″ behind the existing drywall and 1 3/4″ to screw the backerboard to. Once it’s in there it will look nothing like that second horrible graphic – but it will give you the gist of it.

You can see 1/2 of the 2×4 and the dotted line on the drywall outlines the other half. Just screw right through the drywall into the stud to hold it in place.

drywall, backerboard transitionNow you can take your cement backerboard (or whatever your substrate is going to be) and place it up to the edge – leave about a 1/16″ gap between the backerboard and drywall. Then just screw through the edge of your substrate into the other half of the 2×4.

Make sure you measure whatever product you’re using for your substrate. Your existing drywall is likely 1/2″ thick – your substrate likely is not – it is probably a touch smaller. To get them even and on the same plane you can use regular drywall shims behind it.

1/2″ backerboard is rarely 1/2″! It is often smaller – make sure you measure it and shim it out as necessary. Once you get it installed you still need to tape and mud the seam. Just use the same alkali-resistant mesh tape and thinset that you’re using for the rest of the backerboard seams. Don’t know what I’m talking about? Read Installing backerboards on walls for shower tile.

Once that’s all finished you can install the tile as normal, just like the photo below. The transition is directly under the bullnose tile on the edges of the shower. And yes – you can paint right over the thinset if you need to.

Tiled shower with backerboard transition

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Holly Bryan

Hello,
I’ve been reading these posts as I remodel my bathroom and have followed your site for instructions and advice, but this is my first post. My question is how to transition from shower alcove (Hardie Board with plastic sheeting behind it for vapor barrier) to adjacent drywall (90 degree outside corner). The drywall doesn’t overlap the cement board, it meets just to the side of it but has about 1 inch of damage where the rusted old metal corner stripping was pulled off.
My shower tile will end at the corner with a bull nose unless suggested otherwise…

1. Do I use some sort of vinyl corner bead and if so do I thinset the shower side and joint compound the drywall side?

2. Do I just try some kind of flat tape or vinyl strip to build up the damage dry wall side and compound it so the it sets flush with the remainder of the drywall?

3. Can I tape around the corner w/ alkali resistant tape and thinset shower side and joint compound dry wall side?

Thank you for any thoughts….
Holly

Reply

Roger

Hi Holly,

1 or 3 are both viable options. I would prefer 1 just because it’ll give you a more solid corner.

Reply

Matt

Hi Roger,

Thank you for all of your advice. Not able to find an answer to the below questions in your e-books or posts. I am using Kerdi-Board in a 30 x 60 tile shower renovation/build. The walls and floor will be tiled and the ceiling will have drywall.

1) How do I address the Kerdi-Board / drywall seam at the wall / ceiling (e.g., caulk, Kerdi-Band with thinset or taping compound, drywall tape, combination of caulk and tape / K-band, etc)?

2) The short shower walls are furred out so that I have a Kerdi-Board outside corner with a 1″ Kerdi-Board return that dies into the bathroom drywall (will be placing bull nose on this return). How should I address the Kerdi-board / drywall seam (e.g., caulk, K-band, Drywall tape, etc)?

Many thanks in advance!! — Matt

Reply

Roger

Hi Matt,

1. I silicone between the kerdi-board and drywall, the install kerdi-band with thinset.

2. Drywall tape and mud.

Reply

Matt

Thanks Roger.

1)
a) I have leftover Kerdi-Fix. Can I use Kerdi-Fix instead of silicone?
b) When finishing the drywall ceiling, after attaching the K-Band with thinset, do I coat the Kerdi-Band with taping compound or thinset before sanding and painting?

2) So, I will attach the bullnose to the taping compound covered Kerdi-Board?

Thanks,

Matt

Reply

Roger

1. a) Yes.
b) Either one. Both can be sanded and painted.
2. Yes.

Reply

Jeff Stratton

Roger,

Just located your site. Very informative. I am re-doing my 1957 bathroom and shower. I am planning on using Kerdi board in the shower area. I noticed a couple of studs are set back up to 1/4″ in some area of the studs. Is thin set on those studs ok to use to build them out to the other studs instead of using furring strips?

Thanks,

Jeff

Reply

Roger

Hi Jeff,

Yes, you can if you want. Seems like more work to me, but it’s completely up to you. It’ll work.

Reply

Jeff Stratton

Roger,

I have use metal reinforced paper tape in bedrooms that I have renovated. Is this type of tape ok to use in bathrooms?

Thanks,

Jeff

Reply

Roger

Hi Jeff,

There are a lot of different types of metal reinforced tape, as well as a lot of areas in a bathroom. You can use it everywhere in the bathroom other than inside the shower – the metal will eventually rust and corrode.

Reply

Devin

Roger,
What are you using for the shelf inside of the shower niches in the picture above? I have read your postings on shower niches, as well as many others, but have a difficult time finding information on the best materials to use for a thin and clean shelf inside the niche. I have seem many people frame out and use studs for this, but I do not think it looks good; too thick. This looks like just a piece of tile, but what about the unfinished side underneath? This looks thinner than two pieces of tile together. Please let me know some options on materials and process. Thank you so much for the help.

Reply

Roger

Hi Devin,

It’s two pieces of bullnose tile back to back.

Reply

Bob R.

Hi Roger, Here’s a few more ????? on my project. My shower-floor tile will be strata-stone pebble tile (fairly flat, 1″ to 1 1/2″ Dia. x1/2″ thick) random spaced stones glued to 12″ square mesh with interlocking pattern on all sides.
1) Ever used these on you jobs and how easy/hard are they to lay and grout vs. say 2″ x2″ on 12″ mats?
2) You told me earlier to use a 1/4 x 1/4 notched for these I think, right? Now wondering about the grouting and sealing process. Since grout joints around them are totally random widths, from some stones touching each other to some with 5/16″ gapped triangles of space between others, will they be a real pain to grout? If stones are say generally 1/2″ thick, would the grout come up to 75% of that thickness or closer to 90-95% of the stone thickness approx. when I float over and then sponge/wipe them?
3) ?? Sealer applied 1st time after (thin) setting them down (before grouting I think I read so grouting would be easier) AND a second time after grout cures a bit to cover stones and all grout, is that right?
4) Then AFTER all that sets/cures a few days, I was going to screw on my lower hardy boards about 1/8″ – 1/4″ above that finished pebble shower floor surface and go on with the walls topical (Mapei Aquashield) waterproofing. Sound right?
5) Should there be a bead of clear silicone at the 1/8″ – 1/4″ gap at that floor joint to Topical waterproof wall change of plane?
6) At all the upper HBd’s I have already screwed on I left a 1/8″ gap at the 2 inside corners (90 deg.change of plane) and plan to shoot 100% Silicone there to keep the thin-set out and smooth flush and then on top of that I’ll use the 6″ Mapei Reinf. fabric tape (embedding it with Versabond TS) and eventually Mapei Aquashield 2 coats over that…. Is that correct.
7) What size V-notch trowel to apply the Mapei Aquashield 2 coats did you say you use (for the Hydroban in your case)?
8) Regarding 12 x 12 wall tiling, laying out a centerline and horizontal grid system and then individually back buttering All tiles, one at a time, is that a bad way to do a shower enclosure as a first timer? I saw it on YouTube and looked less messy for a novice but probably much more time consuming, huh? Do you get the same adhesion or coverage for adhesion if back buttering them that way without applying any to wall?
Guess I’ve written another book here …. Sorry …. I really appreciate your time doing this …… Bob R.

Reply

Roger

Hi Bob,

1. They are just as easy to install, provided they interlock well. Be sure to stagger the sheets so you don’t see the obvious separation in straight lines. They use a LOT more grout, be prepared for that.

2. It varies with stones. They can go from 75 – 95% of the depth, it just depends on the look you want (provided they still provide proper drainage if the grout line is lower). The higher the grout the less of the stone you’ll see.

3. Yes, but the grout has to FULLY cure first.

4. Yes, provided you used a traditional liner as your waterproofing on the shower floor.

5. No, leave it open.

6. Yes, that’s perfect.

7. 1/16″ x 1/16″. If you can’t find that a vct trowel (tiny notches) will work as well.

It will take more time and it will be messy. If you choose to do that you want to make sure to at least burn the thinset into the substrate with the flat side of the trowel. If you don’t you WILL NOT get the same bonding strength.

Reply

Bob R.

Hi Roger,
(Chapter 3)
One more question about my installation. I have taken extra time to add horizontal 2 x 4′s for extra support of all my substrate edges (1/2″ hardibacker) in my 32″ x 60″ shower redo where I’m doing a Traditional Mud base w/ PVC liner (up 7″ high via notched studs on 3 inside stud walls) using topical Mapei Aquaseal for waterproofing on the Hb boards.
I’m doing the floor mud bed /pebble tile complete (as stated earlier above, see question #3 & 4) and then screwing down my lower 3 backer boards, starting 1/8″ above my pebble tile finished floor.
So here’s my question finally. Won’t the bottom 6-7 inches of these three lower h’backer boards be just hanging there unsupported because of the PVC liner laying behind it in notched studs there at the bottom; I can’t put any screws in this lower 6″ area or would put holes in the PVC liner, right? Above that boards will be screwed every 6″ vertically and 16″ horizontally as studs allow. It just seams to me that the lower 6″ could be damaged by putting pressure or kicking the finished bottom edge as my notching of studs may be a touch more than the thickness of the liner creating a small 1/16″ void between b’board and PVC liner /notched stud area. Is this common and OK or have I screwed up by notching too deep. If so, how do you recommend I correct it??
Thanks once again for your time ,,,,,,, I O U a case of your favorite beer ERRRR!!! I mean chocolate milk. Bob R.

Reply

Roger

The bottom does hang over the liner, and it’s just fine. It would take a concerted effort to damage anything there by kicking it. Once the tile is bonded to the backer it becomes extremely sturdy. The only place you need to worry about a backer being fully supported is on a floor where there will be compression stress put on it.

Reply

Bob R.

Hi Roger,
Great site! My project is a tear out of a leaking 60 x 32 prefab. shower pan with the 3 piece 1/4″ plastic 81″ tall panels glued on 2 side walls and 60″ long wall. The base had no overlap lip with only a 1/8″ silicone bead to waterproof it at the change of plane (wall to pan), so when the cheap, poorly supported pan flexed, the silicone eventually separated and leaks occurred. I’ll bet you have received many replacement jobs from this type
of shoddy builder construction, have you?
Anyway, it’s all torn out to studs, new valve and much extra blocking added for joint seams, hardware mounting and stud leveling added. I’m using your ebooks for traditional shower walls and traditional mud/pvc/mud/tile pan AND ebook for liquid topical waterproofing (using “MAPEI Aquaseal” brand). My field tile will be 12w x 9h x 1/4 thick porcelain (laid running bond/brick pattern w 1/8″ (sanded) grout line) with a 3 x 12 matching bullnose tiles (offset/staggered joints) around top and sides.
Enough history……
Question #1) If the flat transition joints to the existing adjacent painted drywall are 1/8″ gap, thin set, taped and sanded per your earlier
instructions above in this forum, can I cheat the border bullnose tiles 1″-2″ onto the drywall (using thin-set) to cover this joint and in effect enlarging my end wall tile width from 32″ to 33″-34″? …. This OK? Any suggestions?
Question #2) Field tile will be 8 full (9″T) rows plus 1 cut (3″H) field row. (I’ve used 81″ as the total hgt. off slab floor, then -3″ for floor mud and tile buildup at bottom and -3″ bullnose at top. Should this 3″H (possibly 5″H if Q1 answer is OK) be the bottom row or top row just below the top bullnose? Which will look better?
Question #3) I’m trying to pre layout and stud up 2 matching 9″H x 12″W x 3″D (full tile size) niche’s but odd stud spacing and pvc vent pipe in this (load bearing) 60″ tile wall won’t allow. After much studying of all the measurements/locations, I figured I can fit in 2 symmetrically spaced niche’s that would be 9″H x 10.5″W x 3″D……. How do you think this would look? Each niche would be 10.5″W with a 1.5″W (x 9″H) cut of tile to the centerline side of the niche? Any suggestions are appreciated.

Time to end this BOOK if written. Thanks for your time …… IOU a chocolate milk or two or three.

Reply

Roger

Hi Bob,

Yes, I’ve done many of those. :D

1. Yes, you can cheat the bullnose out onto the drywall.
2. It always looks better to have any cut rows at the bottom of the wall. They are less noticeable there. When you look at a shower you don’t look at the tile by the tub – you look up.
3. It will look just fine. If you can’t line them up perfectly you can’t do it. Center the niches and the tile around and inside it the best you can. The important thing is to make sure your grout lines follow through. If you do that they look like they belong.

Reply

Bob R.

Hi Roger,
Another question about #1) and #3) above….. Mapei makes a product called Mapei Reinforcing Fabric – a 6″ wide white roll (looks like a very thin fiberglass woven mat similar to the 5″ orange kerdi-band at Home Depot – Lowes), that I was thinking about using along with their Aquaseal liquid membrane to waterproof in and around the 2 niche’s (#3 above) and along the 2 change of plane 81″ inside corners of shower.
Ever used this stuff? Could or should I use this in place of or on top of the 2″ concrete joint tape across the 1/8″ gapped flat board seams and transition seams referred to in question #1) above where I butt up to the existing painted drywall? Should the paint at this joint be sanded off or roughed up before tape and mudding and/or reinforcement fabric application?
Thanks so much for your time and knowledge sharing.

Reply

Roger

The fabric can be used in place of the fiberglass mesh tape. You still need to embed it with thinset. Doing it only with the aquaseal does not reinforce the seams, it only waterproofs them. The paint should be roughed up before using anything over it.

Reply

Connie

Roger
Thanks or advice on transition from kerdi board to drywall.

Another kerdi board question, can I use it to cover my kiln dried 2x4s
On my curb? If so do I adher it to the wood with kerdi fix or thinset?
Ultimately should it be screwed with the special screws for kerdi board with the washers?

Lastly if I kerdi fix is used to at the change of planes on the keri board covered curb, should I still take the kerdi membrane over the curb?

Thanks … Kerdi videos don’t address the kerdi board applications very well
Your help is much appreciated!
Connie

Reply

Roger

Hi Connie,

Just use screws with kerdi-board over your 2×4′s. No need to, but I usually run the kerdi at least up over the top of the curb.

Reply

Connie

Sorry for typo. Drywall corner bead over kerdi fix was option one

Big thing is whether to use thinset on kerdi board side ?

Thanks again

Reply

Roger

Hi Connie,

Yes, drywall corner bead is easiest, or kerdi-band works as well. Use a plastic corner bead, not the metal ones (they rust). Always use thinset on the kerdi-board side.

Reply

Connie

Roger
I used kerdi board in my shower, I am unsure how to transition from kerdi board to drywall on my out site corners.
It is a change of plane of I use kerdi fix and then drywall bras in that corner with mud or kerdi band w thinset and then mud? Second choice seems cumbersome ? Thanks, the dog almost caught fire yesterday!
Connie

Reply

frank

I have a question on fiberglass tape around a window in the shower area. It will be tiled, I have Hardibacker placed all around the window including the sills. Do I use mesh tape on the sill/wall transition? Can’t seem to find the answer anywhere.

By the way. Great site!

Reply

Roger

Hi Frank,

Yes, tape and mud the outside seams on the window sill.

Reply

renee parks

I have the same situation. I don’t understand. What do you mean by the outside seams on the window sill? Isn’t there only one seam (the one between the the cbu and window sill)? Do you mean to put tape and thinset on the actually windowsill where it meets the cbu?

Reply

Roger

Hi Renee,

In the case of Frank’s window his window sill is backerboard, it will be tiled. I am referring to the seam between the horizontal (on top and bottom) piece on the window sill and the vertical piece of backer on the wall, where those two meet. If your window sill is getting tile then it needs to be the same substrate as the wall, and it needs to be taped and mudded. If it is not getting tile then it does not need to be tied together, so you don’t need to tape and mud it.

Reply

Jossy

Hi,

I have tried to research this but haven’t been able to find an answer.
I am re-doing a poor DIY job in my bathroom. I ripped out some vinyl that was stapled behind the tub and the greenboard behind it is undammaged. (This bathroom is almost never used.) I am going to install cement backerboard (over a vapour barrier) over top of the greenboard. Then tile over it.
My question is: Do I have to remove the greenboard? If I tile over the backerboard over the greenboard it will end up being about 1/2 inch from the rest of the walls. Is there anyway to compensate for it sticking out so much? Is there an edging tile that I can use? Or can I use one of those metal strips that goes along the edge?

Any advice would be appreciated,

Jocelyn

Reply

Roger

Hi Jocelyn,

Yes, there are mud edges available which are 90 degree finish trims. You can also use metal edge trims. My question is – why would you. Just remove the greenboard. It solves all the problems and a barrier should not be sandwiched between cement board and an additional backer anyway.

Reply

Slade

Roger,

I was wondering what your recommendation is for an outside corner transition. This will be going from the shower wall (cement board) turning the corner to Drywall. The drywall section is only about 6 inches(essentially is a couple 2×4′s that make a column) and then the entryway begins. I’m following your Kerdi book pdf.

Thanks for your input.

Slade

Reply

Roger

Hey Slade,

I normally run the field tile right to the corner, then use a bullnose piece with the rounded edge overlapping the edge of the field. If you need about six inches another bullnose with the rounded edge on the outside with a grout line between the two finishes it off well.

Reply

Slade

Sweet, I think that’ll work. The drywall side is a bit wider than two bull nosed tiles, so i can probably run a vertical strip of the decorative tile i have in between the two bullnosed ones to fill, sound ok?

So, since that 45 degree corner is a change of planes, do i not grout the corner (where the field tile and bullnosed tile meet), and instead calk?

I really appreciate your help.

Thanks,

Slade

Reply

Roger

Yes, a vertical strip sounds fine. You can grout the outside corner, there are normally no problems there, only inside corners.

Reply

Kris

Replaced alcove tub with new Jacuzzi brand basic tub, no jets. Ripped out an old fiberglass all in one tub / shower. Had to rip some drywall back to the next stud. There is a flange around the top edge and down the front sides. We screwed the flange to the studs around the top and down the front sides. We installed the concrete backer board 1/4″ from the top of the flange. The backer board only goes to the front edge of the tub as this as far as the tile will go. My problem is the green board that we butted to this edge went over the flange and is therefore not flush with the backer board at the outside corners of the tub :censored: . I suppose I could have cut the green board back so that it was butting the flange like the backer board, but this seemed wrong; what would I fill that gap with, mud :censored: ?

My question then is how to handle the uneven outside corners when it comes tiling?

Reply

Roger

Hi Kris,

Remove the green board and cut a channel out of the back of it so it fits over the flange. So the portion over the flange would only be about 3/8″ thick rather than 1/2″, you would cut 1/8″ out of the back of the greenboard to fit over the flange.

Reply

Jaclyn

Hi Roger,
My queation is a follow up to commenter Mike’s. I have taped & mudded my hardie board joints, but now that the thinset has dried some of the tape is showing with gaps in the mesh. It was probably too thin, wasn’t quite peanut butter texture. I am planning on using redgard & putting on at least 3 coats. i used alkali resistant tape & modified thinset. Do I need to go over the tape with additional thinset before I apply the redgard? You had mentioned in Mike’s post that the membrane did the same job as the tape & drywall mud so I was hoping I wouldn’t have to mix up more thinset for under the redgard. Thank you so much for your informative posts! Your answers to questions have also been very helpful!

Reply

Roger

Hi Jaclyn,

Sheet membranes, such as kerdi, do the same as taping and mudding, not liquid membranes. I would skim coat over the bare areas before applying the redgard.

Reply

Todd

Hello,

I am currently working on redoing my upstairs bathroom and ceramic tile install for the shower. I had some questions about where the Durock cement board to Sheetrock and Greenboard transitions/joints meet:

1) Where the Durock and the Sheetrock ceiling meet…what do I do? Fill the gap with silicone caulk? Thin-set? Thin-set with latex? Paper tape and joint compound? Fiberglass mesh tape? Or… do nothing because the tiles will go up to there and cover it anyway?

2) The vertical seam between the Greenboard on the walls and the Durock which transitions at the shower. There’s a little gap between the two. Do I fill it in with silicone to prevent moisure transfer? (if it happens). Do I paper tape and joint compound it? Or do I fiberglass mesh tape and thinset the joint?

What I am worried about is if I fiber mesh tape and thinset these areas, I will need to sand or smooth down these areas upon the Sheetrock and Greenboard after.

Any advice on this? I greatly appreciate the help and thank you very much!

Todd

Reply

Roger

Hi Todd,

1. I prefer fiberglass mesh tape and thinset. Although you can use regular drywall mud if you need to.

2. Place silicone between the two, the mesh tape and thinset to tape it.

Thinset can be sanded and painted (if you prime it) just like drywall mud.

Reply

Todd

Hi Roger,

Thanks for answering my questions. I went ahead and fiber mesh taped and thinsetted the joints, but my thinset was a little weak. I tried to get it to the consistency of peanut butter but it turned out like a thick soup. In any case it dried pretty well in the joints and on the cement board, but the fiber mesh tape is showing in certain areas. I’m not worried about the mesh tape on the cement board itself because tiles will go right over it. Which brings me to more questions I need to ask:

1.) Should I apply more thinset to cover the tape on the vertical joint/gap where the cement board and green board transition? Also at the ceiling where cement board meets? Or should I sand each area and apply joint compound to cover the fiber mesh tape?

2.) Should I sand the thinsetted joints? Do the areas I plan to install tile need to be very smooth prior to tiling?

3.) What should the ratio be for the proper consistency of thinset to apply ceramic tiles? Is it a 4:3 ratio (4 parts thinset to 3 parts water)?

4.) There are some deviations in the cement board as I did not use shims to get the boards even have everything entirely flat. I am about 1/16″ – 1/8″ off at the cement board joints. Is it still possible to install medium to large ceramic tiles in these areas?

Sorry to ask all of these questions, but this is my first time doing a tile install. I just want to make sure I get it right.

Thanks,

Todd

Reply

Roger

1. As long as it’s on there it’ll be fine. It will get more thinset as you set tile anyway.
2. The just need to be flat enough to not interfere with the tile as you’re setting it. The tile doesn’t care how smooth it is.
3. Each thinset has different hydration requirements which will be on the bag. There is no consistent ratio, each is different.
4. Yes, the thinset behind the tile should be plenty to compensate for that.

Ask as many questions as you need to, that’s why my site is here. :D

Reply

Todd

Hi Roger,

Thanks again for answering my questions. I wanted to get some clarification on the prior questions I had asked:

- For questions 1 and 2, I have read that the thinset should be sanded with 25 to 80 grit sandpaper or a rub stone so there are no large deviations on the cement board.

- For question 4, I read it is possible to ‘float’ the thinset on the cement board for some of the taped deviations (as described above).

Can you provide any advice on these statements above?

Thanks again for your help,

Todd

Reply

Roger

Both work just fine. I prefer to sand down cured thinset rather than floating it.

Reply

Terry

Ok this is similar to our project our back wall of the surround that is tiled continues into the room as a drywalled wall. Our problem is I have to shim the cement backer board about 1/4 of a inch to get the cement board over the tub flange. When I do that te cement board sticks out past the drywall. 1/4 inch plus tile plus mortar so I end up with about a 3/8 in gap where the bullnose would end and the drywall will begin. I think it will look bad with the big of caulk line filling the seam. What can I do. The wall has a windo and toliet so add 1/4 drywall to Bring I out would not work I don’t think

Reply

Roger

Hi Terry,

Just stop the backerboard 1/16″ above the tub flange. It will still stick out enough for the tile to go over the front of the flange and will be flush with the drywall.

Reply

Terry

That’s the problem I need the cement baord to be another 1/4 thicker to let the tile to go over the wide tub flange this of course will make the drywall and cement board uneven

Reply

Roger

You said you needed another 1/4″ to get the backer over the flange, not the tile. If you need that much to get the tile over it then the easiest thing to do is install the backer where it needs to be and find something like a pencil rail or other trim piece to fit over the difference on the edge from the drywall.

Reply

Brian

Thanks Roger,

I decided to just go ahead and replace it to the ceiling as we decided to tile up to the ceiling.

But…. I think I screwed up when I cut the drywall on the side. I cut it where the old tile ended thinking I wanted to replace everything that had the old thinset on it. And guess what? That ended up being right over a stud which means the remaining drywall is just hanging there not attached to the stud and moves quite easily. I’ve read enough of your site and books to know this is bad.

I can think of a few fixes and I don’t like any of them much.

1) Try to get a sister 2×4 behind the existing drywall and screw the drywall to it. Actually I like this idea except I think I have a good chance of breaking the drywall in the attempt.

2) Remove more drywall to the next stud, put up a sister 2×4 and replace the drywall. Hard thing here is I have little confidence in my ability to match the texture on the drywall. Anyone sitting on the toilet will be staring right at it and thinking, wow that looks like crap. Maybe if I provide excellent reading materials that can be minimized.

3) Remove the drywall, sister the 2×4 and tile over it so the tile would go a couple feet outside the shower area.. Seems like that would look weird. I could probably remove the bottom third and get a sister board up there and then do a tile wainscoat along the length of the wall, but that is a lot more tile and I wasn’t planning on doing that.

4) Replace the drywall on the whole wall, Yeah, right.

Any other ideas?

Also, I haven’t demoed the other side wall yet as I don’t want to screw that one up. Could I leave a couple inches of the old drywall with the old thinset on it and tile over it? I assume I’d need to sand it first. The concrete board and vapor barrier would go to the edge of the tub and then it would be drywall.

Thanks tons for the help. If you get down to Lyons I’ll buy you a chocolate milk,

Reply

Brian

I just re-read this post a few times and I think what I need to do is remove enough more drywall to slip a 2×4 in there and attach it in the perpendicular orientation to the studs so that the width is against the drywall and the cement board will also attach to it. I may still have to try to match the wall texture but after readin your original post I think that is pretty mush the only way.

Thanks again Roger.

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Roger

Hey Bryan,

Yup, that’s likely your best bet. It’s easier to do that than the other choices you listed.

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Brian

Hi, first time attempt at remodeling a bthroom. This site looks awesome and I just purchased a book bundle. I already have a question. The shower tile I’m replacing doesn’t go all the way to the ceiling and I haven’t decided if the new till will or will not. I’m also not sure what the existing substrate is behind the tile or what is above the tile.

If I decide that the new tile is not going all the way to the ceiling is it okay to not rip out all the existing substrate? In other words is it okay to just replace the substrate behind the existing tile and then overlap the new tile a little bit onto whatever is above the tile now.

I hope the question makes sense.

Thanks!

Brian

Reply

Roger

Hey Brian,

It’s likely just regular drywall above your existing tile. Yes, it’s fine to leave it up there. Your waterproofing needs to go two inches above your shower head, but above that you can have nearly anything you want.

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Rob

Hi Roger,
I’m trying to figure out how to handle a corner transition where a tiled shower wall will meet a drywalled wall. There is a stud in the corner, to which the drywall and backerboard is attached. Right now the backerboard is hung such that it overlaps the edge of the drywall. This means you’d see the edge of the backerboard as you look at the drywalled wall. This is an ‘outside’ corner, not an inside corner. I’d prefer not to have tile on the drywalled wall. Any suggestions on how to handle this?

Reply

Roger

Hi Rob,

Just tile up to wherever you want and mud and paint the corner. Backer can be finished exactly like drywall.

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John

Hi Roger,

I have my cement board installed and the seems have been filled with thinset/tape like your manual says. I bought my tile from the TileShop and they gave me ProShield HPG to “paint” on for the topical waterproofing method. It seems to be the only thing they carry like that. I have not seen you reference this product nor can I find anything about it online other than the fact that it’s from Ottawa Lake, MI by a company called Superior Adhesives and Chemicals. Have you heard of it/should I trust it?

Thank you,
John

Reply

Roger

Hi John,

HPG is good stuff too. I just don’t mention it much because it’s not readily available in most areas. It’ll be just fine for your shower.

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William

Hello. This is a great site and I’m glad I found it on my phone. I have a million questions that I know have been answered before but my eyes hurt from reading all the posts. Im working with bare walls that are studded. I’ve already hung the ceiling.
1. How do I shim the hardboard to make it even with the drywall or do i have to make it even?If its uneven, won’t the tile make it look even?
2. I’m doing a tile shower only and was wondering how far past the shower opening should the go? Does it go past the shower curb?
3. When I butt the drywall and hardiboard how much gap do I need? Also can I butt them on the same 2×4 or should I have another 2×4 put in?

Reply

Roger

Hi William,

1. With regular drywall shims. If it’s 1/8″ or less you can make that up with thinset behind the tile instead if you want to.

2. I normally go 3″ (width of the bullnose) past the curb, but it isn’t necessary. I think it looks better.

3. 1/8″ gap and it needs to be taped and mudded with thinset and alkali-resistant mesh tape. You can use the same 2×4, it’s much easier.

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Craig

Hi Ben,
I am doing a remodel on a shower and was planning on putting the backer board directly over the drywall to save from the work. ( this is a first for me). I have completely removed the old shower enclosure down to dry wall. Plumbing stubs outs are done. I am using a pre-fab shower pan, which can work with my idea of backer board over drywall. The only issue that I face is transitioning at the edges. I would have to transition down 1/2 inch to the dry wall. Do they make bull nose or transition tiles for the deep of a transition? Or is it better to tear out the existing drywall and start with cement backer board to the studs?
Thanks for your help!

Reply

Roger

Hi Craig,

You didn’t mention what type of waterproofing you’re using. If you are using a topical membrane then yes, you can put the backer over the drywall, but I don’t recommend it. It’s better just to remove the drywall. You can get edge profiles that fit over 1/2″ edges, they’re made for mud walls. You can also install a pencil trim along that edge. Personally I would remove the drywall and make everything flush, it just looks better.

Reply

Craig

Thanks Roger! I will start removing the drywall today.
Craig

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Mary

I’m down to the studes in my tub area. On the oputside corners, we cut thru the bottom plaster and plan on using dry wall and wall papering that wall. The area that didn’t have to be rem0oved is 1/2 inch so we plan on using 1/2 drywall. But I thought we should use 1/4 inch cement board in the shower so that when the tiles are on, the outer corner will be flush. Is this ok?

Reply

Roger

Hi Mary,

Yes, as long as it matches up and your wall studs are maximum 16″ on center the 1/4″ will be fine.

Reply

ben

On this transition- I’ve got my backerboard all Redgarded and happy. Then I remembered the transition. Yeah, whoops. I’m great with taping/thinsetting over the transition, but do I need to re-waterproof this area? The transition is two or three inches outside the edge of the tub, so is water going to be an issue out there? Also, I’m not sure I have enough Redgard left to cover it. Do I need to go back and get another $40 tub of Redgard or if I run a bead of silicone down the edge of the backerboard(kind of like what you say to do behind the tile that goes around the fixtures), will that be enough to keep the drywall from getting wet?

Thank you!

Reply

Roger

Hey Ben,

It will be fine without it since it’s outside the shower. You can silicone it to keep it from wicking into the drywall if you want.

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Mike

Hello!

My drywall sub trade who installed the whole house with drywall went ahead and hung my cement board in the shower enclosure. He then proceeded to tapejoints and corners with drywall tape and mud. I’m planning to use the Homelux water proof underlayment for wall and floor anways, covering all this mud with this waterproof membrane. Should I do something to these drywall mud/tape joints first?

Thanks, Mike

Reply

Roger

Hi Mike,

I would scrape and sand it off of there. There is no need for tape and mud behind a sheet membrane, the membrane does the same thing. You can leave it, but drywall mud has been known to disintegrate due to the alkali in the thinset.

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