Installing cement backerboard is one of the more popular choices for a shower wall substrate. Cement backerboards include Hardiebacker, Durock, Fiberboard, wonderboard, and similar products. These materials bridge the gap between expense and effectiveness. When installed properly they will give you many, many years of durable shower construction.
The advantage of cement backerboards is that, while not waterproof, they are dimensionally stable when wet. That just means that when they get wet they do not swell up. Any swelling behind tile is a bad thing. It will lead to cracking grout, tile, and all sorts of bad things.
Waterproofing your studs
To install the backerboard you must have a vapor barrier between it and the wooden wall studs. While the backerboard will not swell when wet, your wall studs will. You must prevent any moisture from reaching them. The preferred material for a vapor barrier would be 4 mil or thicker plastic sheeting which can be purchased at places like Home Depot or any hardware store. You can also use tar paper or roofing paper, the thick black paper used under shingles. Although I personally do not use that, it is an acceptable barrier.
Starting with your bare wall studs on your shower walls simply take your plastic sheeting and staple it to the wall studs completely covering the entire surface which will be inside your shower. You can also use silicone instead of staples to adhere it to the studs. Make sure you overlap all the edges. Just hang it all up there like you’re hanging wallpaper. You want it covering the framing enough that if you were to spray the walls with a hose the wall studs and framing would not get wet.
At the bottom of the barrier you will want it to overlap on the shower side of the tub or shower base. That is you want it so that any water that runs down the plastic sheeting will roll off into the tub rather than behind the tub. Overlap the lip of the tub or base and silicone the back of the barrier to keep it in place.
Installing the backerboard
Now for the backerboard. Lay out your backerboards for the best fit on the walls. They can go up vertically or horizontally, it makes no difference. With a regular tub surround with a five foot back wall it is usually easier to use two horizontal sheets along the back wall and one vertical on each of the sides. (This assumes 3 X 5 foot backerboard sheets.)
All backerboards are cut by scoring and snapping. You do not need a saw for them. While there are special scoring tools specifically for this you can easily do it with a regular utility knife. While all these backerboards are essentially identical in their effectiveness as a substrate, some are more easily cut. Durock, in my opinion, is the most difficult. I personally prefer hardiebacker or fiberboard. Make sure you check the website for whichever you choose for specific instructions.
To fasten the backerboard to the framing you have a couple of choices. A lot of professionals simply use galvanized roofing nails. While this is perfectly acceptable, I prefer screws over nails when possible. Hardi makes specific screws for their backerboard which can also be used for all backerboards. These are manufactured with ribs beneath the head of the screw which help it cut into the backerboard and countersink so the head is flush. If your local big box or hardware store carries them, they will be in the tile section. You can also use just about any type of corrosion resistant screw. Anything that can be used for an outside deck can be used for your backerboard.
Fasten your backerboard to your shower framing with a screw or nail about every 8 – 12 inches. I would also suggest using a straight-edge along your wall while doing this so that you can shim out any areas where the wall studs may not be straight. The flatter your backerboard is installed, the easier your tile installation will be. Take your time, the beer isn’t going anywhere.
Allow for movement!
You do not want to butt the backerboards against one another. You need to leave a small gap at every change of plane. That includes corners, walls to ceilings, and walls to tubs or floors. There needs to be room for expansion and contraction.
Wood moves – always. It’s just a fact of life. The secret to dealing with the movement is to ensure the movement will not interfere with the tile. Leaving this small gap will allow for movement of the sheets enough so that they do not force against one another and push out. While the backerboard itself is very stable, you are still attaching it to wood.
If you have a tub or shower base you will also want to stop the backerboard about 1/8 inch above the lip. You do not want to run the board over the edge of the lip because it will cause the backerboard to bow out and your wall will not be flat. It will also allow the tub or shower base to move a bit – it’s attached to the wooden studs as well. Tubs also move when they are filled with water. You need to allow for that movement.
I usually leave about a 1/16 to 1/8 inch gap between the sheets of backerboard. This allows for thinset to lock into the entire thickness of your backerboard when you tape and mud your seams. We’ll cover that part in a minute.
Don’t allow for movement! (Confused yet?)
If your shower framing is such that you cannot place the edges of all the backerboards directly over a stud you will need to add more studs. You may do this with regular 2 X 4’s screwed to the present framing vertically or horizontally as needed. You must make sure that every edge of the backerboard is supported so if the wall is pushed or leaned on in that spot it does not move. You want solid walls.
Final step
The last thing you must do is mud and tape your seams. Similar to regular drywall all of your in-plane joints must be taped. To do this you just use regular thinset and alkali-resistant fiberglass mesh tape. You can find the tape in the tile section – it’s similar to regular fiberglass drywall tape, but it specifically manufactured to be alkali resistant. Make sure it is alkali-resistant because your thinset contains alkali which will gradually erode regular tape thus defeating the purpose.
There are two ways to address the corners. The industry standard, and the way you should do it, is to tape and mud the corner joint as well. Most backerboard manufacturers recommend this, as do the handbook standards. I only do that about half the time – I’m a rebel like that. 
*The other half of the time I only tape and mud the in-plane joints – the gaps in the same wall, not the corners. With the corners I fill the gap with silicone. I do this to allow the different planes of the walls to move in different directions, which they will do whether you like it or not. Allowing this movement in the substrate compensates for excess stress in certain applications. This is something that I do, it is not industry standard and you will likely not find anyone else recommending doing this. So when you get the conflicting information about this – that’s why. 
Fill all the gaps in your seams with thinset (you left gaps there, right?) then embed the tape into it. Then go over the tape with more thinset to smooth everything out. This will lock everything together and give you a continuous, solid substrate for your tile. That’s what you’re looking for.
When properly installed cement backerboards will create a rock solid, extremely durable substrate for your tile installation. Taking time and care to solidify what is behind or beneath your tile is the only way to guarantee a lasting installation. Your tile is only as durable as what it is installed upon.
As always if you have any questions at all please feel free to leave a comment.
Need More Information?
I now have manuals describing the complete process for you from bare wall studs all the way up to a completely waterproof shower substrate for your tile. If you are tiling your walls and floor you can find that one here: Waterproof shower floor and wall manual.
If you have a tub or pre-formed shower base and are only tiling the walls you can find that one here: Waterproof shower walls manual.
Roger,
I am really trying to get this right, but having trouble understanding. You said, “If you have a tub or shower base you will also want to stop the backerboard about 1/8 inch above the lip. You do not want to run the board over the edge of the lip because it will cause the backerboard to bow out and your wall will not be flat. ” I noticed that now the backerboard does come out a bit, so i took it off. Your instructions then say that I need to leave a 1/8 in. gap between the tub lip and the bottome of the backer board. I understand that, BUT that will mean that there is a gap between the bottom of the backerboard and the top of the tub lip (using redgard as a waterproof barrier). Do I fill this small gap with the thin set I am using to tape and mud my joints? Also, if this gap is there, btwn the BB and tub lip, do I start the first row of tile 1/4 in. from the actual tub, then use caulk to seal that? And lastly, in this gap that you speak of leaving, I have installed the metal and plastic clips that came with my tub. They are screwed to the studs. They apparently help secure the tub to the stubs. The directions to the tub also said to set the tub in a cement base. I have done all this. These clips are also helping the backerboard to bow out at the bottom. Do I need them? Need to get this right and get this show on the road because my wife is having a baby in 20 weeks and there is way more to do besides this bathroom. Thanks for the great info and guidance to have provided.
Hey Aaron,
I think I haven’t been clear about the two different types of tubs in this scenario. Since yours is an after-market (remodel) the tub flange – the part that is vertical that is attached to the studs – will sit proud of the studs. If the tub flange is flush with the studs you can run your backer over them almost to the top of the tub rail – the horizontal part of the tub at the wall. I sometimes use the term ‘lip’ to describe either of these without realizing that it can confuse people who don’t stand in showers all day long.
If you are using redgard you need to have the backer about 1/8″ above the tub rail. This means that it should be placed down over the flange. To get the backer to sit flat from top to bottom and not bow out over that flange or those fasteners you need to shim out your backer from the wall studs. You can do this with regular drywall shims or furring strips, either of which is available at big box and hardware stores. Measure the thickness of either the flange or the clips to determine how much you need to shim them out.
If your flange turns up the wall about 1″ (which it should) you should be able to get rid of the clips and carefully drill holes through that flange to attach it directly to the studs. Just two along the back wall and one in the center of each side wall is plenty. As long as you set the tub in cement that will be plenty. Do not overtighten those screws! You may crack the acrylic. If installed properly you actually shouldn’t need fasteners along the flange anyway, the bottom of the backer will hold it in place just fine. It does need to be solid and fully supported (the cement bed) if you choose to eliminate the side fasteners.
You can then shim out the backers enough to cover the flange and run them to about 1/8″ above the tub rail and silicone that gap all the way around the bottom.
Do not fill anything right next to the tub with thinset. Acrylic tubs flex as they are filled and used, it will crack out all that thinset.
Did I just confuse you more?
Hi Roger,
Great site. Apologies if these are overly basic questions, just want to make sure I’m following the direction on the gap between tub flange/BB and tile/tub deck.
I’m installing Hardibacker and leaving 1/8″ gap between the tub flange and the BB, and 1/8″ between tile and tub deck. Should I caulk the gap between the flange and the BB, and also caulk between the tile and the bathtub deck? Would I leave a weep hole in both locations (between flange and BB, and between tile and deck)? Or just a weep hole at the tile/tub deck?
Background: I’m using Aquabar B paper for my moisture barrier (running it down the studs, flange and attaching with a bead of caulk at the tub deck). Any downside to using Aquabar B paper?
Thanks in advance!
Hey Greg,
Aquabar is good stuff. You’ll be fine with that. You do not need to caulk between the tub flange and BB. The barrier will prevent any problems there provided it is properly lapped over and attached to the flange. You can if you want, but if you do then yes, you should leave weep holes to moisture can run out from behind the BB as it travels down the aquabar. You don’t want to trap it above that line. It would be best just to forego a bead of caulk there and simply caulk the bottom of the tile leaving weep holes.
OK, I am feeling a little stupid now. I was planning to put 4′ x 8′ 1/4″ plywood under 4′ x 8′ 1/4″ HBB with 4-6 mil poly or plastic sheeting behind the backer board for our corner shower. If I eliminate the plywood will 1/4″ HBB provide the strength needed for the tile?or should I use 1/2″ wonderboard. If so do i need to place horizontal blocks between the studs at the seams? Thanks, John
Hey John,
1/2″ wonderboard would be fine on 16″ studs, once you get your board and tile on there it isn’t going anywhere. The 1/4″ tends to flex a bit too much between the studs. No need for blocks with the 1/2″
The 1/4″ is not likely to be strong enough for your shower walls unless you have studs closer than 16″ apart. Like 8″ apart, for instance.
Thanks, I am building this 3′ x 4′ corner shower over an acrylic /fiberglass shower pan. Do I apply furring strips on the studs down to the pan nailing flange and overlap the flange with the backer board of just put the backer just above the flange and fill in the gap over the flange with thin set ? I think I understand about the weep holes and the plastic barrier. Thanks for all the great info- might help me from f-ing things up
You can do either. If you leave the backer above the flange do not fill that gap with thinset – the tile can just hang there. If you fill it with thinset the movement from the pan tends to crack it. Then your shower sounds crunchy. Either way works fine. I do both – if the backer meets a wall on the same plane I’ll not usually fur it out – that leaves the backer further out than the drywall. If they both meet corners I’ll normally fur out the backers.
Hi Roger,
We gutted the bathroom in a 100+ year old balloon framed house in preparation for installing ceramic tile on the floor and shower/tub enclosure, new fixtures, etc. When the plaster and lathe were removed, it exposed the studs with no insulation and only thick horizontal plank siding on the exterior of the house (no exterior sheathing). The end of the tub alcove is on an outside corner. We were going to stabillize the exterior corner on the inside with some plywood before applying the hardibacker. I just read on your site that this is a no-no. Do you think the exterior corner walls will be stable enough with just the 1/2″ hardibacker attached to the studs with a vapor barrier in between? What kind of insulation do you recommend on the exterior walls? We are also debating tubs…what is your opinion on Vikrell, Americast, or acrylic?
Thanks,
Carolyn
Hey Carolyn,
Hardi will add no significant structural strength to your house in that corner. If you need additional shoring you can do whatever you need to between the studs – including adding more studs.
The problem with plywood is it will expand and contract significantly with humidity and temperature differences, never a good thing behind tile.
To be honest, to me a tub is a tub. If you can get something other than acrylic I would do that – it’s just more sturdy. Make sure whichever you choose is installed correctly with concrete or thinset beneath the base if it is not cast iron. This supports it completely and eliminates the creaks and groans often associated with stepping into an unsupported tub.
I am redoing my bathroom and installing a L-shaped framless glass door. There is one outside cover in which i ran the wonderboard all the way to cover the drywall return. My question is:
How do i finish the corner. I wasnt planning on using a bullnose as i wanted to have the boarder tile end flush on the corner. Can I use cornerbead? If so how do intall to the wonderboard without cracking it?
Hey Joe,
Yes you can use a corner bead. Nail it as usual on the drywall side and you can use thinset on the shower side – it’ll stick.
I’m planning on tiling my shower walls above the tub with 1″ tile mosaic and after reading this I am a little confused about the hardibacker install. The flange on the tub is ~3/4″ if I hold the backer 1/4″ above the flange as the hardiback site sugggests, or even 1/8″ as you metioned I am going to have an entire row of tile with no backer behind them. What is done in this situation?
I’m thinking Ill have to pull the backer down over the flange and live with the slight bow, or maybe try and cut some of the material off the back side of the backer so it stays level.
Hi Jacob,
Shim out your backerboards from the wall studs the width of your tub flange. Use either strips of wood or regular drywall shims (behind your moisture barrier) to bump it out enough to not have that bow at the bottom. Then you can leave your backer 1/8″ above the tub rail and still have solid coverage behind your tile. And caulk that transition – not grout.
Home depot’s yard sticks are great 1/4″ uniform shims. They’re about $.60 each I started using wood lathe which is cheap but varies in thickness and quality so the yard sticks are much better. Their paint stirers are also great if you need 1/8″ (they’re actually a hair thicker than 1/8″) and they’re free (so what if you go up to the paint desk and grap two handfuls without buying any paint?). Lowe’s yard sticks cost more and their paint stirers are made of a weaker wood (like balsa).
Great ideas Tom! Thanks.
I went to look and my friends install. He has some old guy doing his remodle of bathroom. He kocked out walls and reframed them. He used an acyrlic pan so save $$ and he wasn’t sure if they would do a mud one right. The previous one leaked. My question is the guy 2×4 framed the shower. Did all the plumbin. But covered the walls with plywood. He said it makes it stronger?? Over kill I thought . He’s using Tyvek house barrior as a moisture barrier then 1/2 cement board.He said the Tyvek will keep moisture out butif any vapors get pass it will go back through so no mold. Tryong to say plastic will create mold cuz it doesn’t breathe? I was looking at it and mentiod it’s not flush with the wall now. But he said he was using a bullnose or something to blend it. Kinda wierd?? But my question is will he have problems with leaks later?? He doesn’t have the project done but I would wonder?? I’ve never read anything about that methiod. More like wire and lathe stuff?
Hey Mike,
Tyvek is an air infiltration barrier, not a moisture barrier. He needs 4-6 mil poly or plastic sheating behind the backerboard. And the plywood should be done away with. It does make the wall stronger – no doubt. But if the wall is properly framed with 16″ oc studs and backer properly fastened it isn’t gonna go anywhere.
IF any vapor gets through the tyvek it will be soaked into the plywood! It will not ‘go back through. Once the vapor gets through the tyvek it will soak straight into the plywood, it will swell, it will begin to grow and crack grout and tile. And there will be considerable mold and mildew between the tyvek and ply. Moisture is there and mold loves wood – it’s a no-win situation. There should never be plywood behind a shower wall substrate. There should never be tyvek behind there, either.
He’s probably talking about a mudcap bullnose, they have a 90 degree angle and are used to hide the thickness of a mud wall. Handymen use it to hide plywood behind the shower wall.
I honestly don’t know if he will have problems with leaks – I don’t know how everything is lapped. I do know that he is currently cultivating a mold factory in my opinion. The wire and lath stuff you’ve mentioned is a mud wall – nothing to do with what he has going on. He is probably thinking that he is simply substituting the backerboard in lieu of the mud – it doesn’t work that way.
Roger
I am getting close to tiling but I am getting nervous about getting the moisture out from behind the backerboard. I used plastic sheeting on the studs but now I am wondering if a topical product, the paint on kind, should have been used. Besides pissing my wife off for another delay, is there any harm in using both methods. I know it is overkill but I fear failure.
Thanks
Hey John,
If you install a topical waterproofing you will trap the backerboard between two waterproof layers with no way to dissipate. This may lead to mold, mildew, and all sorts of nasty stuff you don’t want in your shower wall. You need either the barrier behind the backer (which you have) or a topical over it, one or the other – never both. Why exactly are you nervous about getting moisture out from behind it? As long as it properly overlaps your tub flange and you put weep holes in the tub-wall joint then your shower is fine. It will last. Really.
Now stop pissing your wife off and get to work.
Hi, iv read alot about this on other websites and iv got to tell you i really like the site you have here, good info. Im going to silicon the back of the moisture barrier to the tiling flang on the tub then when i run the cement board down ill leave a small gap above the flange where the barrier comes out and over the flang. My question is when I tile what do I do between the gap of where the tile comes down over the flang and meets the tub? I know ill leave a gap there, but I wouldn’t think I would want to Silicone that due to the fact the water wouldn’t be able to get to the tub from the moisture barrier. Thanks again for the site
Hey Tyrel,
You need to leave weep holes in your silicone around the tub. Read through this and it will show you how: Weep holes in tub tile installations
Ha, Thanks and man ur fast on replys, wich is awsome, but right after I posted this question I was browsing through your wealth of information here and ran across that page. Answering my own question
Sweet! Glad I could help! (And by that I mean I’m glad you found what you needed)
Hey Roger,
Thanks for all the great info. This will be my first tile job. i bought an old house and put in a new shower stall in and I have an old tub and i want to tile the walls around both. The problem is there is no lip on the tub. What should i do? Do i need a lip? Can i buy some sort of flashing and silcone it to the edge for a lip? Thanks for your help.
Hi Sandy,
Depends on the type of barrier you’re using. If it is a vapor barrier you can fold it out horizontally on the tub rail and silicone the back of it. This way all water will run into the tub and not behind it. If you are using kerdi you can do the same, the fold will be smaller since it will only be beneath the tile rather than the backer and the tile.
Hi Roger,
Thank you for your advise. I am using tar paper then hardibacker. Forgot to tell you that part. i will do the silicone under the paper. Sounds good. Thanks again.
Roger
Don’t know if I have screwed up or not but here goes. I installed the hardie backerboard over heavy plastic sheeting for a vapor barrier. I left the HBB 1/4″ above the tub then caulked between the tub and HBB. (I read to do that somewhere) Also a tub liner is going to be installed over the old tub prior to tiling. Not sure where any moisture is going to go with this tub caulking in place. Should weep holes be cut in the caulking that is in place now and again after the tile is installed and caulked? I am not really sure how the tub liner is going to affect drainage. The good news is if this tile job lasts as long as the original one did, 45 years, I won’t really care as I will be worm food and the next tile job won’t be my problem. The bad news is ,if it falls apart in 5 years I’m screwed. What are my chances of success?
Hey John,
Yes, you should dig out some weep holes for drainage. Do that as well after you install the tile. As long as the bottom of your barrier overlaps your tub flange and you have the weep holes you should be just fine for the next 45 years or so.
Roger
Me again. I just need clairification on joint taping. You stress leaving a gap between panels for expansion but then say to fill the gaps with thinset and tape over them to make a soild substrate. Am I missing something?
Thanks
John
Hi John,
You’re not missing anything – I’m failing to explain it correctly.
The movement I’m speaking of is pressure against the boards. When not taped the seam creates a weak point in the installation. If expansion presses the boards against one another it will bow out along that seam. When filled with thinset, taped and floated over it essentially creates a monolithic wall. If you do not leave that space in there you cannot get thinset between them to tie them together. Here’s what’s probably confusing: I would say 70% of people will not tape and mud the seams – they’ll only leave the gap and tile right over it. If they do that the gap needs to be there or it will bow out as I’ve mentioned before.
If I explain it as leaving a gap for expansion people will do it. If I tell them a gap needs to be left to tape and mud they won’t do it because they don’t plan on taping and mudding it.
Hi Roger,
I think I am going to use Wonderboard for the shower project. I read on Home Depot’s website that this product “installs without tape for ease of use.” I am getting confused. To tape or not to tape……We built this house 22 years ago, the builder used regular drywall, All is well, never a problem. Now we want to retile and all the various materials and methods to use in lieu of drywall are overwhelming. I used to be smart, now I feel really, really dumb. I need a dose of smart juice… and a little handholding..maybe.
Hey Michael,
Wonderboard is covered under ANSI A118.9 which are the specification for cementitious backer units – even says so right there on custom’s web site. If that is the applicable standard (which it is) you must tape and mud the board after installation. Not too sure what HD is using to reference that or for which application but if the manufacturer states that is the ANSI standard for successful installation of their product then I would take their word over HD’S.
You’re still smart – it’s all the people throwing too many different things at you. Just have fun.
Roger,
Many thanks for all your help. You really know your subject matter So I am ready to get on with this now. By the way, what do you know about fuel injection, how about income taxes, nosey neighbors, and gall bladders????
Hey Michael,
Fuel injection – if you get oil on one of the injectors your truck will run like shit. Income taxes – Too high, too many, and too useless. Nosy neighbors – Rent a circus elephant to shit on their lawn. Gall bladders – I hear they’re fairly useless, unless they begin hurling stones.
Roger,
Wow!! You do know everything, and you’ve got a sense of humor. You should rent yourself out for parties!!
Roger
Is there a prefered method of taping in the corners of the backerboard or is just 1 – 2″ wide length of tape adequate?
John
Hey John,
You need to get some alkali-resistant mesh tape sold in the tile section. Use thinset to fill the seams and corners, place the tape over it, then smooth it out with thinset and the flat side of your trowel. The 2″ wide tape is adequate in most installations.
We are DIYer’s doing a Kerdi Shower. We installed the backerboard but did not put vapor barrier between backerboard and wall studs. We will be using the Kerdi membrane. Do we need to take down all the backerboard and put up a vapor barrier?
Hey Kris,
Nope – no barrier behind a kerdi shower. You need either a vapor barrier or a topical membrane (kerdi), one or the other, never both.
Thanks. Second question: we removed a 40 year old shower that was tile on cement on wire mesh and therefore very thick. We kept the original studs and replaced the shower pipes exactly where they were. Now that we’ve put up the backerboard the black, plastic, round piece on the hot/cold spout (I hope I explained that well) is not flush with the backerboard. It sticks out about 3/4 inch. In the installation pictures with the hot/cold faucet that black, round, plastic piece is flush with the backerboard. Are we in trouble if we continue as is or should we do something to bring the wall further out to make it all flush?
Hey Kris,
It depends on your particular plumbing fixture. If the handle(s) can be installed and placed against the tile then it’s fine. If not either move the backerboard or move the plumbing back. Figure about 3/8″ – 1/2″ for the depth of your installed tile. Just place your handles on there and see how far towards the wall you can install them. If they’re 1/2″ or closer you should be fine.
Roger
This is probably the same problem that Dustin had but my problem is the difference in the elevation of the existing wall and the Hardie backerboard at the top of the shower. I shimmed the studs to accept a 1/2″ backerboard but found out later that the HBB is not a half inch thick. The difference at the match is 1/8″. Can I just shim out this area with thinset while taping the joint? Also this joint is about 1/2″ thick do I fill that with thinset also prior to taping?
Thanks John
Hey John,
Yes, you can float that out with thinset. No need to fill that gap with thinset, just tape over it and float it all out as flat as you can get it and you may want to use a larger notched trowel for your tile installation to keep the tile all on the same plane from top to bottom. The larger notches will give you more play to adjust things as you go.
Roger: I am replacing the walls and tile in the shower stall. Noticed after removing the first row of tiles on the wall at the shower floor level that they were applied to a morter or cement made foundation that ran the length of the shower floor around all three walls with the original green board resting on top. The top of this supporting foundation to the shower floor is around 3″ and all but falling apart. Question: If I take it out and just set the backerboard down as far as it will go (it that void) with the original water proofing material under and behind it and enforce with more plastic underneath and behind, will that be good enough to start the tiling work – or should I re-build those ledges.
Hey Mike,
As long as your waterproofing membrane is intact and working correctly then it will be fine as long as you rebuild the ledges. If you want to pack mud (dry pack mortar) into the voids which would be created behind the backer if you took it all the way to the floor that would also work fine – again, as long as your membrane is intact. Not sure what type of waterproofing material you’re speaking of so I’m assuming a normal 40 mil pan liner here. If that is not what you have then those method may or may not work. I would need more specific information about the original waterproofing to let you know.
How does one fill the small gap left by the drilled holes in the backerboard for shower head arm and valve body?? Silicone or thinset?
Hey Andre,
Silicone is best. It does depend on your waterproofing method, however. With a normal moisture barrier use silicone. With a liquid waterproofing membrane use silicone. With sheet membranes like kerdi use the proper gasket.
I’m afraid to ask my question, but here it goes. I found your site after I installed my backerboard. After the fact I have realized that i probably needed to shim my studs a bit more than I already did. I had my BB hang over my tub flange quite a bit and now there is a bit of a slant at the bottom. I have already taped and mudded my seams as well. At this point I am ready to put up my 12″ porcelain tiles, but I’m worried that the slight slant at the bottom will make the finished product look bad. I don’t think I will any issues with waterproofing, I think I might have a cosmetic issue. Will the final product have a noticeable flaw? If so, is there anyway of fixing this without starting all over?
Hey Dustin,
You can simply use a larger trowel like a 1/2″ x 1/2″ and install it with just enough thinset at the bottom of the wall to make sure it sticks and build out all the tiles above that row to be plumb with the very bottom. In other words the tile above the bottom row will be a bit further out from the wall.
I will be stopping my backerboard an 1/8″ above my shower pan due to the offset. When I install my tile, I assume that I will overlap my tile down into my shower pan area? Also do I want to install a caulking under this gap or should I just leave it open?
Hey Trevor,
Yes, install your tile over that gap all the way down to about 1/16″ above the tub then caulk that (1/16″) gap. No need to fill the entire thing with caulk or silicone – it’s not going anywhere.
Ok, that sounds good. Now here is a silly question. Where my tile is overhanging below my backerboard, how do you grout that bottom area of the tile. Where it is below the backerboard and nothing is directly up against the tile behind it. Does that question make sense?
It makes complete sense. Grout it just like you do the rest of the shower. You may need to pack a little more into that joint but the grout actually adheres to the sides of the tile – not the substrate beneath it. It’ll stay – I promise.
Sounds good. I didn’t realize that the grout would attach to the tile sides instead of whats behind it.
On a second note. I have an outside corner where my shower wall divides itself from the jacuzzi tub. On the shower side, it will be all tile. On the tub side it will be a combination of drywall and tile. I am going to tile the entire face of the dividing wall. I will be putting cement board on the entire face. This is going to give me a corner on half of that dividing wall that is drywall butting up against cement board. Below the drywall section it will be cement board butting against cement board.
Do I just install corner bead the height of the wall and finish the corner with mud for the drywall portion and thinset for the cement board portion?
Hope that I did not confuse you.
Hey Trevor,
I’m not confused. A bit dizzy, maybe, but not confused.
You can use a corner bead provided you use the plastic ones – not the metal ones. They’ll rust. Use thinset as your ‘mud’ on all of it, water won’t affect it. You can paint right over it wherever you need to.
In the house that we bought, has a showder, on the wall is plywood and he has it covered with some thing, , how do we put glass tile on the wall
W
Hi Patricia,
Plywood is not an approved substrate for anything in a shower – ever. Doesn’t matter what he put on it. That needs to be taken out and a proper substrate put in it’s place.
Glass tile installation is a very specialized skill, at least if you want it to last. It requires a proper substrate, proper thinset, and proper installation technique. It is not the same as just sticking ceramic tile to the wall. Contact the manufacturer of your particular glass tile and ask them what they’re recommendations are for each one of those – that will give you a base starting point.
Roger,
Thank you for your site, I would not be successfully doing anything in my bathroom without your assistance. With tha being said, how does one seal the area around the shower control and the shower head?
Thanks in advance!
Hey Jordan,
Depends on your waterproofing method. I’m assuming that since you left this question on this particular post you’re using backerboard with a moisture barrier?
(Friggin’ quick, aren’t I?)
When you cut the holes in the barrier for your valves cut them as close as you can to the valve body and you can either silicone the barrier to the fixed body of the valve OR … You can silicone the barrier to the BACK of the backerboard around your valve. This creates a ‘dam’ or barrier so when water runs down the barrier it will run around the siliconed area. You should cut the hole for the pipe (shower head) after you have the barrier up, that way you can simply poke it through the barrier and it will be exactly the same size and tight against the pipe. Then either silicone the pipe or the barrier to the backer.
I have a question with your traditional metoid of install. If you use the plastic on the wall framing. And put BB with screws to attach to the 2×4. You are breaking the seal which is protecting the wood???
Hey Mike,
Yes, it does break the surface of the barrier, but it doesn’t compromise the barrier. Think about it like this: Take a piece of plastic and screw it to a 2×4. Now if you take a close look at the plastic around the head of the screw you will see how it ‘puckers’ out all the way around the head of it. If you lay a piece of backerboard over the plastic it will lay on top of the pucker all the way around the head of the screw. In other words the backerboard is in direct contact with the plastic around the head of the screw and the plastic puckers in, away from the backerboard, toward the screw. Now if that is on a wall the water will run down the plastic barrier and around that pucker, not over the top of it and toward the screw.
I understand it’s a bit difficult to visualize but if you actually, physically do that with the screw, plastic and 2×4 and look at it you will see how it works.
Hello Roger,
I just finished install in my backer board and was sure to leave a 1/4″ gap between my BB and the shower pan. I am planning on using thin set and redguard and I am wondering if I should be filling that gap with thin set or will that allow moisture to wick up to the backer board?
Thanks Scott
Hi Scott,
I usually won’t fill that with thinset – I’ll stop the thinset at the bottom of the backerboard due to the possibility of wicking as well as the different expansion and contraction of the different materials (the acrylic and backerboard/tile). Provided your shower is properly waterproofed you can leave that space open and it shouldn’t be a problem.
If you stop the backerboard above the pan and use redguard. You don’t need to worry about the water going into the pan because with the redguard no water is getting into the BB to drain?So you don’t need weep holes there? The tradition metiod with the 6mill it goes into the pan and is silicone no weep holes then the bboard and tile which needs weep hole because the bb is wet and need to drain? I’m trying to fully understand.
Thanks
Hey Mike,
If you are using redgard you need to silicone that gap between the BB and pan flange if it’s a tub or acrylic base. If it’s a mud bed then you don’t. You always need weep holes in the silicone joint at the bottom of your tile installation on a tub or base. Water will get behind the tile. Whether it hits redgard immediately or saturates BB then hits a barrier it still needs a way to get into the base or tub and down the drain.
Hello Roger,
I am remodeling my walk-in shower and attempting to use Hardiebacker 500 cement board to replace my existing drywall material along with culture marble.
For culture marble installation using Hardiebacker 500, tape joint using Type 1 mastic instead of thinset is acceptable? What type of sealant should I use to seal the bottom of the board that meets the shower pan and should I use the same sealant on the 3 joints on the cultural marble?
Since I am using Hardiebacker 500 and cultural marble, would I still need to use a plastic barrier behind the Hardiebacker 500 board?
Regards,
Jose
Hey Jose,
Cultured marble is not actually marble – it’s a dust infused acrylic or plastic product. It is waterproof so long as you use 100% silicone (or the manufacturer’s approved sealant) at all the seams. No need to use the plastic or seal the board at the shower pan – the product is waterproof. It also, in turn, happens to be air-proof, meaning you probably shouldn’t use mastic behind it as it requires air to cure. You should not tape the joints with mastic – it won’t do any good.