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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Randy

I fear is made a fatal mistake. I have installed the hardibacker in the proper areas. While dry walling the wallboard I noticed I didn’t get a good anchor stud where the shower glass is installed. Any suggestions?

Reply

Roger

Hi Randy,

Heavy-duty drywall anchors (the steel ones) will hold your glass just fine.

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marie

Hi: my husband is attempting to replace an old shower in the basement. We decided to keep the old base since it was in good shape. We bought a surround and glass door to use with that base. The cement backboard does not meet up evenly with the drywall…what can we do?

Reply

Roger

Hi Marie,

Shim out the backerboard with drywall shims over the studs.

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Patrick

Roger,
I think I have it now. Just using the bullnose and not worrying about the bullnose going to the very edge of the wall. I will then have approximately 3/8“ of wall extending beyond the bullnose edge. How do I finish the wall off? I have already place Auqadefense on it. On the other leg I would still like to put the bullnose on the edge of the wall because I have approximately 6 ¾” of wall space between the edge of the wall and the tub. Will it look correct if I do that? If you still think I should place the bullnose against the tub, how do I finish the approximate 4 ¾” of wall that will be exposed? One last clarification that my wife pointed out to me. There is approximately a 1/8” width variance between the top and bottom of the leg. This is due to the leg angling out slightly towards the bottom of the tub leg. I think you mentioned a ½”.
Thanks again.

Reply

Roger

If you want the bullnose to the end of that other wall then take it out there. It’ll look fine. You can skim-coat over the aquadefense with regular drywall mud, then finish it as you would regular drywall. Cut the the bullnose on that first side so you have a consistent 1/16″ gap between the bullnose and tub, whether that is 1/2″ or only 1/8″. Just cut the bullnose to the tub. Keep the outside of the bullnose on a level line and cut to the tub. If your bullnose is 2″ it’ll be 2″ piece at the top, and the bottom of the bottom piece will be 1 7/8″.

Reply

Patrick

Roger,
I completely understand now and I thank you for answering so quickly and even on a Sunday!

Reply

Lisa

Hey there,
Quick question – if we are continuing the tile behind the toilet and sink (like a wainscoting), do we need to paint (or prime) before we put the tile up?
Thanks so much! Lisa.

Reply

Roger

Hi Lisa,

Nope.

Shortest. Answer. Ever. :D

Reply

Wayne

AWESOME site!

I’ve got a new tub installed in an alcove – 3 full sides plus 1′ on the 4th. The tub I got could be used in an “under mount” fashion – dropped into a finished deck, because it has a nice side view, ~2″ lip. But I have an alcove, which it can do as well. Manufacturer picture: http://www.americanstandard-us.com/assets/images/productImages/amstd/alternates/standard/1745.prd.s.alt.003.jpg

I’d like to keep a row of bullnose tile on top of the rounded tub edge to keep the theme of “tile above the tub” like the rest of the surround. With this solution, I’d have 1-9/16″ of wood (and hardibacker) to support the 3″ bullnose that can only be hovering over the tub (and sealed with silicon) . Nice edge out, silicon covering the square edge. Maybe I could even silicone while thin-setting the bullnose for a little support. I just don’t want the tile to bust loose if someone sits on it. Or the tub flexes.

The other option is to attach tile to the top of my 5′ long knee wall, let it cure (even grout it?) and slide it under the tub. But then I’m tiling that top before its 2′ wall…

In either solution, I will ensure I’m supporting that tub edge, as it won’t support any weight on its own. It will need to rest firmly on the 2×4 or tile. Oh, and follow your idea on the magnetic access panel…

What are your thoughts?

Reply

Roger

Hi Wayne,

Not quite getting what you’re attempting to accomplish. If you are setting the bullnose horizontally then provided you have complete coverage of thinset beneath it the tile will not move and the compressive ability of the thinset will be MORE than enough to support the tub when filled with water or when someone gets in it. If you are installing it vertically then simply attaching it to the wall 1/16″ above the tub, letting that cure, then siliconing the gap between the two, will be just fine as well.

If it’s something else you’ll need to let me know what that is – it’s early, I haven’t had any beer yet. :D

Reply

Wayne

Sorry, my words are not as good a a picture, so I tried to upload what I’m trying to describe.

I think you understood the 2nd option I was going for – put the tub on the tile and we are good to go. With this option I’m just seeing that I have to do that first, then finish building the wall and tile the wall up to the bottom of that bullnose.

But option 1 is laying the bullnose horizontally over the *top* of the tub – bringing the top of the knee-wall high enough to be adjacent to support that bullnose. The drawing image I uploaded shows the bullnose will hang out over the tub about 7/8″. So only about 1-1/2″ will be bonded with thin-set to the very narrow hardiboard.

Maybe my pictures will be worth a thousand words in trying to explain what silliness I’m trying to invoke here.

Thanks!

Reply

Roger

You can not bond the bullnose to the tub, it will not last. The tub flexes way too much.

Reply

Roger

Hi Wayne,

It is always better to have the tile under the lip of the tub, with the tub resting on it. More clean finish to me, although either will technically work.

Reply

Edna

I meant 1/2″ sheetrock:)!

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Roger

Hi Edna,

You can waterproof sheetrock with the kerdi membrane. If you don’t want to use kerdi the sheet rock needs to be removed and replaced with backerboard waterproofed with either a barrier behind it or a membrane over it. You need to tape and mud (with thinset and alkali-resistant mesh tape) the transition between the sheetrock and backer.

Reply

Edna

Question: I’m building a new standalone shower(no bathtub). Contractor has already placed 1/4″ Sheetrock on walls. What are next steps to install ceramic tile in shower? Does sheet rock need to be removed or modified to place backer board? Also, I plan to take tile 1-2 feet above shower head, what is necessary to transition from tile to Sheetrock at this point? Anything special? Thank you.

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Anna

if installing tile in a shower all the way to the ceiling, the contractor has put the backer board 12″ below the ceiling and put the tile on that last foot directly on the sheetrock. Won’t the moisture from the shower
effect this later? He said the tile company recommends it?
What is your opinion?
anna

Reply

Roger

Hi Anna,

Provided it is two inches or above the shower head it will be just fine.

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Mike

HI Roger. I have an issue I hope you can help with. Bathtub shower combo getting renovated. 8Ft ceilings. old tub removed. old tile and greenboard removed. original tile only went up 6ft, so the remaining 2ft of greenboard is remaining that goes to the ceiling.
My plan was to replace the tub and tile fully up to the ceiling. My issue is, I came home to find the plumber got the new tub installed, but the tub has an 1″ gap between it and the exposed studs. Tub is flush on the stringer, as well as on the short side where the plumbing is. Its the back (your butt facing side) that has that gap.
So, (a) if I hang the new cementboard on the butt side of the tub, to be flush with the wall and the remaining 2ft of board going to the ceiling, I’m still going to have a 1/2″ gap to the tub. And I obviously want to be able to tile down over the lip of the tub.
And (b) if I were to shim the studs so the drywall reaches the tub lip, there’s going to be a difference between the new board and the old. What can I do? Even if I remove the 2ft on the butt facing side, I’m still going to have the new cementboard sticking out all the way down to the floor. how do I properly transition?

Reply

Roger

Hi Mike,

Is there any way you can push it 1/2″ to the backside so both ends are flush with 1/2″ drywall?

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Chris

I am installing hardibacker board on a wall around a tub that has insulation with the paper face facing in. This wall is on the short end and is an outside wall. Is it ok to use redguard over the backer board or should I remove the paper face before installing the hardie?

Reply

Roger

Hi Chris,

It will be fine to use redgard over that wall.

Reply

Tom

Roger I have made much progress. Hardi board is all installed as well as all drywall which butts up to the edge of it within an 1/8″. My tile will end right outside the tub, with my Hardie board extending several inches beyond that.

Do I use drywall tape and drywall mud on that seam where the two come together since it is in the dry area and beyond the to be placed tub/shower doors? This would be the vertical seams.

Additionally, is it good practice to run a bead of caulk in the corners before thinset and mesh tape is used? Seams I might have read something about it.

Thank you.!

Reply

Roger

Hi Tom,

Yes, regular drywall mud and tape for those seams. Yes, I place a bead of silicone in the corners before taping and mudding, it keeps the thinset out of that gap.

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Rick

Same questions again Roger. Just finished regard on walls, ready for tile. Plan on using 2×2’s on shower floor and 12×24’s on shower walls and bathroom floor. Still deciding if I can afford a slab to cut solid pieces for the top and sides of the curb but if not will use the 12×24’s. In what order should I tile, this includes the bathroom floor? Sorry for the repeat, don’t want my head to explode!! Thanks.

Reply

Roger

Hi Rick,

I do all the floor tile (bathroom and shower), then do the curb, then shower walls.

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Donald

I’m placing subway tile on sheetrock walls that have been painted. The paint looks firm and the walls will not get wet. Should the paint be a concern? I intend to use a good modified thinset.

Thanks

Reply

Roger

Hi Donald,

Provided this is in a dry area like a backsplash it will be just fine. I normally recommend sanding or scuffing up the paint a bit, but thinset right to it is usually sufficient.

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Patrick

Roger,
I am tiling around my bathtub and the tile will be extending out to an outside corner where I will be placing my bullnose. On the other side of the corner is drywall. How do I finish this? Do I use a metal or plastic corner bead and then use mud on the drywall side and thinset on the cement backboard?
Thanks

Reply

Roger

Hi Patrick,

Plastic corner bead with thinset on the tile side, regular drywall mud on the other side.

Reply

Patrick

I installed my durock horizontal. I have 2 seams I need to tape. Do I need to place 2X4’s between the studs to support these 2 seams?
I will be placing silicone in the inside corners of the bath area but do I still tape the inside corners with thinset?
Thanks again.

Reply

Roger

Hi Patrick,

If you have 16″ oc studs on the wall you don’t need blocking behind the seams. Yes, you tape and mud the corners over the silicone as well.

Reply

Patrick

I will be bringing the tile right up to the ceiling in my bath area. Do I need to tape between the cement backer board and the ceiling and then use thinset on the cement backer board and regular drywall mud on the ceiling? Or do I just bring the tile up to the ceiling within the thickness of my grout line and caulk it?
Thank you for your time.

Reply

Roger

Hi Patrick,

Just take it up to within 1/16″ – 1/8″ of the ceiling and silicone it.

Reply

Patrick Kelly

Roger,
The width of the leg on the one side of the bathtub measures approx. 2 3/8” at the bottom and 2 ½” at the top. I am using a bullnose that is 2” wide and my grout line is 1/8”. So at the bottom I have 3/8” space between the tub and the bullnose and towards the top it is ½”. What would you recommend me to do with this small space since there isn’t enough room to place a piece of tile in this area? The leg itself is approx. 14 ¼” high from the floor to the top of the tub.

Reply

Roger

Hi Patrick,

I would put a piece of tile in there. You can grout it, but it’ll likely crack. You can silicone it, but it’ll look like hell. You can cut a 1/8″ or larger piece of tile, at this point that really is the best option. If you’d have noticed that before tiling you could have bumped the bullnose in 1/2″ and simply ripped the bullnose down to fit properly.

Yes, I know you didn’t want to hear the last part. :D

Reply

Patrick

Roger,
I have not started tiling because I didn’t want to regret making a bad decision. Glad I waited. I need a little clarification on the cutting of the bullnose. Do you want me to rip 1/2” vertically off the backside (the side facing the tub) and then still align the factory edge of the bullnose to the corner of the wall? I am assuming you are trying to make room for a bigger piece of tile. If this is correct, I will have to rip all of the bullnose as I go up the wall. If all of this is correct, will I need to do the same thing on the other leg? There is more wall space on the other leg where I can easily place a bullnose and tile. I am concerned that if I do not cut the bullnose to match the other side, it would not look correct since the bullnose on the other leg is narrower.
Thank you for time.

Reply

Roger

The bullnose inside edge (the portion facing the tile and tub) should be placed directly against the top, outside corner of the tub. Rip the bullnose down length-wise as it goes down the uneven tub to the floor to maintain a 1/16″ gap between the back edge of the tile and the tub. On the other side place the bullnose, again, against the top outside corner of the tub and do the same. It doesn’t need to be placed directly against the corner of the wall if you have an outside corner there, just be concerned where it meets the top corner of the tub. If you do that on both sides it will look even, even if it isn’t. Where it meets that outside corner of the tub is where it will look uneven. If it’s 1/2″ off on that side and against it on the other side it will look uneven, even if it is against the wall corners.

Tom

Your “drywall to backer board transition” was just what I was looking for, but I have a question. When installing the 2×4 sideways, the only thing holding that 2×4 in place is screwing it to the existing drywall, correct? Suggestions on how I keep the 2×4 in place while screwing through the front of the drywall? Do I just hold the back of the 2X4 while screwing through the front of the drywall?
Thank you!

Reply

Roger

Hi Tom,

Yes, that is exactly how you do it. Once you get it screwed to the drywall it won’t go anywhere.

Reply

debbie

My tub wall was retiled with subway tiles incorrectly.The dry wall and cement backing was too thick and jutted out too fare and all the tiles where crooked and thick and uneven. I hired other people to fix it. They camr in and now its straight but thet never connected the tiled wall to the exhisting wall and now there is a gap between the two and the exhisting dry wall surrounding the tub is now jutting out half an inch in front of the tiled wall which they have already used bullnose tile on and finished the edges. What can i do to make the wall and tile wall flush and have them meet? Does tile always have to lay on top of exhisting adjoining wall or can it be inset a bit? Do I need to hire another persin to do this again for the 3rd time? How do I make sure they dont mess it up?
Thank you for your time!
Debbie
Thank you!

Reply

Roger

Hi Debbie,

They obviously did not shim the backer out to be flush with the drywall – that’s where your problem lies. They can be inset from the drywall, but it may create problems if moisture gets to the edge of the drywall. At this point the only thing that can be done to make them flush is the tile removed, the substrate shimmed out flush with the existing drywall and everything reinstalled. It just depends on how much your willing to live with it. It can not be properly fixed if that is not done.

Reply

Tom

Thank you Roger for responding. I was thinking I had to shim because my drywall is 1/2″ and Hardie board is .42″ Just feather it out instead with the proper compound?

While I have you here :-); the backer board goes 1/8 above the tub edge right? The tub according to the directions is secured with stainless steel washers and screws at the tub lip to the studs. Does the tile end up covering those? I have pictures.

I found out the tub lip to the back wall was not bend the same after I fastened it. The center area is flush and the ends I had to shim before securing with screws and washers. I really can’t move the tub because of ita plumbing, but maybe I could bed the lip out on the ends and remove the shims???

This has been an adventure!

Reply

Roger

Hi Tom,

Thinset works best to flush out stuff like that. I would leave the tub as is, since it isn’t very workable, and shim out the backer so it is flat and covers the areas you need covered. Lapping the backer, or leaving it up, depends on your waterproofing method.

Reply

Tom

Follow-up to just what I just asked. IF I shim out the green drywall to meet the backer board below, it will be out of alignment with the 10′ drywall on the right. Again, your thoughts?

Reply

Tom

Hi Roger,

My 10′ drywall ends 34 7/8 from the tub wall. My plan is to put 1/2″ Hardie Backer board up within 2′ or so of the top of the wall above the tub. IE., just blow the shower head. Above the shower head green drywall.

How best to handle the transition in both sets of drywall on the sides? If I shim out the backer board to the right of the tub where the 10′ drywall is, I assume I have to shim it out above on the right side where the green drywall is going to go.

Wood shims are used for this if that is the case? Your thoughts on the whole process?

Thank you.

Reply

Roger

Hi Tom,

I don’t understand why you’re shimming out the backer – to meet up with the drywall? They should be the same thickness. Drywall shims are used for it. Your backer and waterproofing should be a minimum of 2″ above your shower head.

I’m just not understanding what your shimming or why.

Reply

J B

I am confused. Everything I read about backer-board products says they are water resistant, not water proof; hence the membrane between the backer board and studs…So why is there no barrier required between the edge of the backer board and the sheet rock at the edge of the shower wall? Without some type of barrier, won’t the moisture in the backer board seep into the sheet rock?

Thank you

Reply

Roger

Hi JB,

Not normally. The transition should be outside the wet area, and water doesn’t run sideways, it always runs down.

Reply

Greg

Hi Roger,
Thank you much glad you’re out their helping

Reply

Greg

Hi Roger,

I hang Hardie backer board in the shower walls, cement board seam and drywall seam meet right outside of the entire tub. The two dont meet flush and i plan to tile 3″ past the outside of the tub and down the wall because the shower tile is the same as floor tile. So my question is how do I fix this without removing the cement board and shimming it. Do I just lay a thicker layer of thinset when laying tiles so the tiles will be flush or do I try to make the walls flush with thinset and let dry and then tile. I have taped thinset seams as u have said and waterproof all the shower even beyond where tile will be placed. But since I didn’t see the seams weren’t flush til after hung I figured I can correct this but now secwguessing myself.
Thank you

Reply

Roger

Hi Greg,

You can do either of those – they will both work just fine.

Reply

Joshua Ferris

Hey Greg, how did this work out for you? I have the same problem where I have installed my cement board and coated it with redgard but I am now worried my backer board and sheet rock are not flush! I was hoping the redgard would have kicked it out a bit but that stuff is thin and it didn’t…So, did you end up build out with thinset or did you butter your tiles thicker? Should I just keep rolling on redgard to get it to build…If you did built out with thinset did you reapply redgard on top again? Is this solution even possible or will my walls be no longer flat/flush? I can’t wrap my mind around buttering the tiles thicker since they have to be troweled/grooved to adhere? How thick could I possibly go to flush the overlap for the transition? Man, if only I had flushed the walls to begin with…Perhaps I could just tile right up to the dry wall and try to make the drywall looks nice with the transition and paint..what to do, what to do… thanks in advance…

Reply

Carl

The tub was prepared with cement board an inch below where I would be tiling in order to hide the seam behind the tile. I used modified Versa thinset to mud the seam between the sheetrock and the cement board. I applied spackle in some areas only on the sheetrock. The sheetrock will be painted
Since it appears that I will have a lot of tiles left over, I plan to lay subway tile up to 9 inches higher than I initially planned. With this new plan I will be laying the subway tile above the cement board onto the sheetrock and there are a few spackled areas.
I read you can apply Redgard and in another site they recommended a good primer over the area. I have the primer and the area is not as likely to get that much water.
Question 1
What do you recommend?

Question 2
I read online that many use 4 mil plastic behind the cement board and other places that is not mentioned. What’s the deal on that?
Thanks

Reply

Roger

Hi Carl,

You can install the tile right onto the sheet rock. Above the shower head it doesn’t create an issue at all.

To waterproof a shower you need either a moisture barrier behind the backer (4 mil plastic) or a topical membrane over the face of it – never both.

Reply

Mark

Where my bullnose tile meets the drywall, there is about a 1/8 to 3/16 stand off from the buildup of thin set to compensate for irregularities in the wall. Should this area be grouted, silicone caulk that is color matched, or acrylic color matched caulk since paint will need to go on? With the later, should I paint first and then caulk?

Thanks in advance!!!
Me and my beer(s)

Reply

Roger

Hi Mark,

Ideally siliconed, but against the drywall on the back of bullnose it can usually be grouted without any issues.

Reply

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