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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Ladida

Hi there,
I would like to ask if you have any working experience with Goboard (Johns Manville) as a backer board? I am excited about this stuff and it is much cheaper then Schluter, BUT I wanted to ask a pro before I start my project.
Thanks and keep on elfing!

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Harold

Our contractor removed old tile in our shower down to studs, installed DurRock and then 12×24 inch tiles. Instead of applying thin set to walls he placed a glob of thin set on each side of the tile and stuck it on the wall., leaving a cavity all along back perimeter of each tile.
Should he have applied thin set to entire surface of the tiles and user 3/8 in trowel to distribute thin set evenly on tile? Does his method create problems later?

Should he have used Red Gard of other moisture barrier on DurRock walls before tiling?
Thanks

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Flo Downing

We have just had a fiberglass shower/walls replaced w/ceramic tile to the ceiling. The adjoining walls are stained ash paneled. Where the edge of the tile comes to the paneling there is a gap almost 1/2″ between the wall & tile. The setters we used don’t finish that. I can get my little finger in the gap. What can we do to cover that gap between the edge of the tile & the wall? Thanks for your help.

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Maureen

I’m ready to install the durock in the small shower stall in the basement. It’s only 32X32.
1. Do I have to have the bullnose side down at the bottom, where it meets the fibreglass shower pan? Or can I install the durock vertically and leave the rough edge at the bottom?
2. And, what’s the best way to seal the bottom of the durock where it meets the pan? Just 100% silicone? (I’ll also be using hydroban to waterproof)
Thanks for the information. It’s appreciated.

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Derek

Ok, so is some movement of the 2×4 ok as I start fastening the backer and drywall to it? I put the stud in the whole length of the wall. It seems like it is not solid enough, and will make the tile not last because of the movement.

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Wade

No remove the backer and the stud and reset the stud firmly in place the tiles will turn to crap almost in no time on you. I hope that helps even though it’s more work

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brian

Roger,
First time trying to put up backer board around my 60″ shower. Got it all put in on the 3 walls, sealed the board in and then on one of the walls the transition from the backer board to the drywall is uneven! Not sure what to do. Please tell me I don’t have to take out that backer board after all that hard work. Thanks!
Brian

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Wade

Did the wall have a tub with a tub surround on it before ? If so it could be the drywall compound that was used to transition the wall into the tub surround, what I did to fix that problem was cut the drywall off that has more of a bulge to it then you can add some more backer in that spot and it should even up with the rest of the wall. I only had to cut out another couple inches of wall made it an even 3 and hooked the backer to the stud

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brian

Wade,
I took everything out and started from the studs. It didn’t have a tub surround. Not sure how cutting out the drywall which is sticking out farther than the backer and then adding more backer is going to make the transition even? Wouldn’t that just make the transition uneven farther into the wall away from the tub? Thanks for your quick reply?
Brian

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Wade

Its ok, mine had surround. Which whenever the surround came out the new backer that went into its place was about 1/4 inch indented from where the tub met the wall originally. I cut out that section of wall because it was easier than trying to sand that much off. When I took that chunk out and replaced it with the 1/2 inch backer it sat flat with the original wall and the backer in that area. Sometimes homes have 3/4 inch drywall too, and sometimes adding another 1/4 inch sheet will compensate for that if that’s the case.

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Wade

I guess if there was a way to post a picture it might be more helpful to you to show you what I was talking about.

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brian

I’m really frustrated right now because the drywall sticks out about 1/4″ where it meets the back of the tub backer board. Not sure if I can tile it and put some bullnose at that transition to cover that difference or not? I just DON’T want to take out that whole wall of backer board and put in shims and start over the process of gluing, screwing, and sealing again! If you can think of anything that would bring that wall to plumb against the drywall, let me know. Thanks Wade!
Brian

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Wade

Yeah you can fix that without tearing down the old for sure. If it’s 1/4 inch all the way around you might have 3/4 inch drywall and if you’ve sealed it, I would try mortaring and fastening another 1/4 inch sheet right over the old. Seal the fasteners again. You are more than welcome to reapply all around where it meets up again or since you’ve sealed the other one well a thick bead of silicone between that part could work also.

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Wade (frizodanizzo)

I misread that so its only one wall that’s having the issue ? Is the lip of the wall even with the rest of the wall ? You can always take a ruler or straight edge even a small level if there’s a large gap there at the end and the rest of the wall. I would suggest devising a plan in cutting that piece out at least it’ll save you some time also, though you’ll have to seal the top of the backer where it meets when you get a piece that’ll fit flush between the wall and the backer. just scope it out a bit try seeing if it’s level with the rest of the wall above it. Let me know just @gmail the extra word where my name is if you need any extra help or if you want to send a few photos of it.

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brian

I think your first suggestion is my only chance of redemption. Just so you know, it’s uneven from ceiling to floor where the transition of the drywall meets the backerboard just outside of the tub on the back wall away from the showerhead. The drywall sticks out about 1/8″ – 1/4″. So you think just applying another piece of backer board over the existing one will even it out? Thanks Wade!

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Wade

You could try that, or also look into the way to cut that part of the wall away also that’s uneven and replacing with a piece you know is. I would look it over a bit do a couple quick measurements, and checking the level. Mostly it’s going to come down to what you think is easiest for you and also making it to where it doesn’t cause further complications. I cut away a part mostly because I didn’t want to chance my backer or wall being uneven somewhere else also. So you just have to keep that in mind while you’re looking it over. To cut or not to cut lol.

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Wade

Shoot me an email with a couple photos if you have time it’s on the last post

brian

I guess my confusion is that if I cut the drywall out, what do I replace it with that will make it even to the existing backer? If I put drywall back in there, it’s back to where I started. If I put backer in there, then I’m uneven farther into the wall away from the tile. I have no good answer for sure!

brian

Wade,
I took everything out and started from the studs. It didn’t have a tub surround. How do I add a photo and where do I send it to? Not seeing your email? Thanks.

Liza

We are redoing our bathroom and the tub we had had the 3 walls built into it. When we pulled the tub out there was no dry wall behind it just the studs. Do we have to put more dry wall up and then the backer board or can we just put backer board up??

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Bill D

Hi Roger, I gutted my small 5 x 8 bathroom. Starting a remodel from a clean slate. Tiling 3 walls to the ceiling for a new shower where a tub once was….Using 1/2 Hardie backer for these 3 walls. I will ultimately transition from the Hardi backer to green board for the remainder of the bathroom. For all transitions from Hardi backer to green board, I will use drywall tape and mud. In addition, I am leaving the drywall on the ceiling and will cover with 1/2 green board. Studs are 16″ on center. Will I have any issues using 1/2 green board over the existing (nail pops everywhere) drywall?…..or should I just demo the ceiling and use 5/8 green board? Do you see any other issues with my approach?

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stefanie

I tore down my rotted shower walls the tile went behind the floor tiles .. they are tiny square ones .. I put up backerboard which sits on a concrete 2 iunch sorta so called edge .. ithe board and cement is flush but when I put the new tile against the wall there is a small gap between floor and tile the new tile wants to slide behind the floor tiles what do I do

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Roger

Hi Stefanie,

Not too sure what you have going on there. Can you build out that gap using deck mud to get everything flush before setting tile on it?

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Mark

This is a follow-up to Jackie’s question regarding transitioning from cement board to drywall. Given the effort to make the entire cement board surface of each wall a monolithic structure by using thinset and mesh at the seams of the cement board, will there be a potential cracking issue at the seam between the cement board and drywall if the drywall isn’t part of the monolithic mass of cement board? And even if you use thinset and mesh at that seam, will the drywall move with the cement board, or will the drywall tear when the monolithic mass of cement board tries to take the drywall with it?

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Roger

Hi Mark,

It sounds like you have WAY too much movement in there to be concerned with something as small as a drywall transition. :D Drywall and backer will expand and contract at different rates. However, taping and mudding the changes of plane with either drywall mud or thinset will be more than adequate to hold them together without problems.

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Daniel G

Hi Mr. Floor Elf Sir!

I recently installed .41 inch backerboard next to 5/8 inch drywall without using shims. I now understand this was a mistake! Is there any way to make this joint work (such as a schluter and thinset with no tape) or am I completely doomed to going backwards and replacing the backerboard to properly level?

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Roger

Hi Daniel,

You’re doomed. Unless 1/4″ backer over the existing will flush it out for you.

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Rick

I am redoing my bathroom and tearing out the shower walls. First question is what is the best boards to use to avoid mold. I have heard several options and some from what I was told would be overkill. (1) Only tear out the existing mortar and apply mortar and chicken wire over it–no need for tear out (2)tear out to studs and use greenboard mortar/chicken wire over it (I always thought greenboard was frowned upon because of the humidity and moisture) (3) greenboard covered with redgard and don’t really need mortar/chicken wire because it would be a floating wall (4) using backerboard with mortar and chicken wire. I have heard about denshield boards but they are rather expensive.

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Roger

Hi Rick,

Why are you intent on mudding your walls? No, greenboard should be nowhere near your shower. Densshield boards are a hell of a lot less than redgard. You should remove everything down to the studs, shim out densshield to flush with your bathroom walls, then install tile. Forget the chicken wire and all that.

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Susan Jimemez

We hired someone to do our bathroom and he forgot we wanted the tile off set and he tiled half up one wall of the shower when we noticed it. He then took the tile off and it reaped up some of the green board behind it and he covered it with joint compound which he said would be like cement and he tiled over it and said that there was no need to put new green board. my husband and I are worried about mold. Is this okay to do and if so should we make sure to seal the tile and grout twice after he is done tiling so mold doesn’t occur.

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Sissy

Hi, I am tiling shower walls in a basement bathroom. I had already installed green board before I decided to tile. Is it ok to put the cement board over the green board? I sure hope so because I worked on it all day?. I did put a moisture barrier over the green board before I installed the cement board. Any advise would be much appreciated.

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Roger

Hi Sissy,

Not really a good method, but it should be fine.

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Cheryl

Hi, I’m redoing my shower. Im using mold and resistant drywall. I don’t want to take it off now but, are drywall screws ok, can I apply a thinset over the drywall and use waterproof ing membrane after. I know its alot but drywall is up.

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Roger

Hi Cheryl,

You can use schluter kerdi over drywall. That is the only approved waterproofing membrane for use over drywall.

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Richard A

Is it ok to stack 1/2″ (.42″) and 1/4″ to transition to 5/8″ drywall? Anything need to go between them?

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Roger

Hi Richard,

Yes, you can, and no, nothing goes between them. But it would be easier to put 1/4″ (actually should be 1/8″) shims over the studs, then install the 1/2″.

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Jackie

Hoping you can help! So we are completely redoing our whole bathroom in our old house. We are planning to tile in the bath all the way up to the ceiling. We are in the process of installing the cement backer board but have just realized we are unsure on how to handle the joint between the backer board and the ceiling. Can you give me some tips on this? We came up with the idea to use drywall in the last 6-8 inches so we could just use drywall tape and mud, but seems there should be an easier way. Also I’m fearful there will be a bit of a gap between the wall and the ceiling(the old tub surround must’ve been thicker).

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Roger

Hi Jackie,

You can use regular drywall tape and mud from the backer to the drywall. It works on backer as well.

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brian

Just sent 2 pics of the area. Thanks!

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Wade

If the wall is thick only at the part it meets the backer but not as thick above it this where the straight edge comes into play. If you see a gap there’s a bow so it could be some drywall compound where maybe a tub was at some point. A lot of bathrooms I’ve been in usually have them in those areas where they’re trying to hide the tub into the wall itself even after being torn out there might be the couple inches of compound still around it creating that gap you’re getting. If you cut that out the bow or bulge in that spot no longer exist so when you put a non compounded piece of drywall or backer in its place it should flush up with the rest. In the event it’s level for some odd reason and no gap the wall is just thick then and doing the backer over backer would work perfect.

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Wade (frizodanizzo)

It’s what’s in parenthesis at gmail.com

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