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.
I am tiling my shower 4 inches past the tub. Using cement backerboard. Is it better to run cement board past my tile or stay short and run waterproof drywall up to it. Wondering the best place to seam it. Thanks, Dave
Hey Dave,
The best place is always an inch from where the tile will end. It is always best to have cement board everywhere you’re installing tile around a shower. Not imperative, but better.
Thanks Roger, So the cement board will go an inch farther than the tile if I am reading this right? Grreat help, Dave
I meant the tile will go an inch past the backer so the tile will cover the edge. You can do it whichever way though, you’ll just need to finish the seam if it’s outside the tile.
Hi Roger,
We have spent literally days (I’ve lost count) putting up the hardiebacker. The walls are not at all even so we’ve had to shim almost every 2×4 and of course we had to install several more to have a place to attach the backer board. The good news is that the kids’ bath is the place to be in a tornado. The bad news is that we’ve finally gotten it almost all up only to see that it’s not level with the drywall at the last section. You may suggest attaching backer board over the drywall on the last few feet, but as luck would have it, it’s the same wall as the door so there is door trim to contend with. The tile once it’s installed — if we ever get to that point — would be flush with the door trim if we did that. Furthermore, we had 1/2 inch between the edge of the tub so we decided just to run the drywall under the backer board. It’s at the end of the tub opposite the shower head and it’s about 4 inches outside the tub so there shouldn’t be a big issue with water, but I’m wondering if that will make for instability in the tiling. We’re at our wits end and are open to just about any suggestions. A vertical line of quarter rounds wasn’t in our design plan, but if you tell us that’s the best thing to do, OK. Any advice would be welcome. I hope this makes sense and can send a picture if necessary. Thank you.
Hi Deborah,
I hate that.
There are a couple of options. You can use the 1/4 round if you have to. A better option might be one of schluter’s metal edge trims. They are made to have the lip out toward the face of the tile and, once the tile is installed, the tile is flush with the edge of the trim piece. Install it backwards over the edge of the hardi so it would be essentially a trim piece for your backerboard. It will leave a clean aluminum edge all the way down the side of the backer and you can finish that edge of the tiled wall the same as the opposite edge. you can install the tile right over the leg of the trim piece just like it was part of the backer.
Thanks Roger. Hopefully we can find the trim at the local HD or Lowe’s.
anyone knows the perm. rate for any of the cement boards mentioned in the articles above?
By the way, this forum is a cornucopia of knowledge!!!
Hi Doroteo,
Cement backerboards do not have a perm rating because they are not waterproof. They are water stable, which means they do not deform when wet. Water does not compromise the structural integrity of cement backerboards. But steam, water vapor, and water will go right through them.
Hello,
Need Help!. My Tub is 60″ long….Opening for tub (between studs) is 60-3/4. So 3/8 inch space between tub and studs …front and back. Existing drywall is (2) sheets of 3/8 in. drywall or 3/4 thick. From the edge of the stud to the edge of the tub flange (where the tile overlaps) is 5/8. Currently I have the tub up against the 5 ft backwall….should I move that away from the wall 3/8 as well?……What do you suggest I do
Hey Steve,
I would center the tub between the studs on opposite walls and either use 1/2″ drywall or shim out the 3/8″ drywall by 1/8″ to bump it out over the flange lip.
Not sure if your following me: But if the tub is centered between the studs….my measurement
from the studs to the tub flange (where the tiles overlap) is 5/8. Now if I use the thick hardibacker that is actually 7/16″ and figure 1/8″ for mortar and 1/4″ for tile that’s 13/16 or .81 thick. and the existing drywall is 3/4 or .75….will that be alright?
Now for the 5 ft backwall….I should probably pull it away from the wall also… so it’s tub flange is 5/8 from the stud also….yes?
Oh, I gotcha. Sorry, long day. Yes, you are correct. I was thinking you had it placed against the studs on one side. Yes, that transition will be fine. And yes, if you want a uniform look on all three walls then you should pull the back away as well.
Hi on the shower walls the studs edge are approx. 1/2 inch from the outside edge of the tub. The tub also has an approx 1/2 inch think lip. I am guessing that I need the edge of the backer board to line up sttyraight over the inside edge of the lip (about 1 inch from the studs) so i will have a straight vertical edge to tile over the tub lip.. What should I use for a shim on this?
Thanks Paul
Hi Paul,
You can use strips of 1/2 plywood or even strips of 1/2″ drywall to shim out the drywall. As long as your waterproofing goes over it you can use anything that will add up to 1″ with the thickness of your substrate.
Roger . A follow on question. If I shim out the shower wall the extra 1/2 inch to make it flush – how do I handle the transition where the non-shimmed sheetrocked wall meets the tile edge over the backer board which is now thicker because of the shim I added?
Thanks you so much. Paul
Roger, I didn’t complete my last reply and maybe this should be in the transition part of your website, but since I started it here.. In addition to tiling around the tub/shower alcove, we have been planning on tiling up the wall about 42 inches. So this problem of uneven walls becomes even more complicated. I understand how to make a transition if the tile is stopping at just beyond the edge of the tub/shower, but ALL THE WALLS have to match up if we are tiling around the room. My fingers are crossed that you are not going to tell me I have to take down the backer board that’s already up just to shim it. Thanks again.
Sorry, didn’t see this one before I replied to your last one. Same answer applies, though. Sorry, I’m full of good news, huh?
And you probably already knew that too.
So you’re saying the tub sits inside the drywall – not to the studs? If that’s the case, and you plan on tiling all the way around, you can either shim out all the walls (outside the shower as well), push the tub against the studs on one wall and shim out the other enough, or have a 1/2″ jog in the tile installation at the edge of the tub back to the tile outside the tub. The tub should set directly against the wall studs (but you already knew that) and isn’t normally a problem if your walls are not in the same plane with the rest of the bathroom (they end at a corner right outside the tub). But tiling the entire bathroom and having the tub sit incorrectly against the wall is going to create problems which require a significant amount of work to be unnoticeable. Is the tub not five feet long or is the space larger than five feet? One of them is incorrect.
But you already knew that too.
I’ll bet this is a FAQ: So, if I pay for your plane fare and lodging, would you PLEASE do my tiled shower floor and walls????!!!! Please say yes. Thanks. It’s so overwhelming. I know you’ll do it properly and I can then shower in peace. It’s only a little trip to California.
Hi Wendy,
Sure – that is a FAQ. But food would have to be included (you ever see a Marine eat?). I’m never a cheap date.
Of course food is included in the deal!! I’ll get back to you on this.
Oh- and no, actually, I have never seen a Marine eat!
Another question roger if you don’t mind. So a add a moisture barrier enough that I can spray it with a hose but what about the hole for the mixing valve and shower head? I doubt I can get the plastic behind that.
You don’t need plastic behind it. You want a bead of silicone all the way around them between the plastic and the backerboard. That way any water running down the wall along your moisture barrier will run around that bead and down into the shower. You don’t need to worry about water going directly into the hole – water doesn’t run sideways through the air.
It will hit the backer and wick back down into the tub.
Hi rodger
Great site I have a few questions
Fist my project I am installing a 36. Inch single threshold shower basin. For the walls I am using 1/2 inch hardi backer board and 1 inch glass tiles on mesh backing.
1st I dident install a moisture barrer I know I am taking it down to add one. But my question is can I reuse the hardi or do I need to start over I used hardi screws?
2nd the basin fits nice and snug against the studs my friend stopped the hardi at the top of the lip of the basin I feel that he should have continued it at least part way over the lip? I believe he intends to have the tile continue over the lip but this seems unlikely since we are using 1 inch glass tiles. So my question is should we pad out the studs or bend the hardi an 8th of an inch so its inside the shower basin lip?.
3rd how much is to much of a gap between boards or in corners we will be muding and taping.
Thanks a million alex
Hey Alex,
It depends on what kind of shape your hardi is in once you remove it. Hardibacker can normally be reused whereas products such as durock cannot – they tend to crumble and leave giant gaps where the screws were.
If you are using 1″ glass tile you need to have that hardi down to at most about 1/4″ from where you will stop the tile so at least 3/4 of the bottom row is supported. Ideally it should run all the way down to your stopping point. It would be better to shim out the studs rather than bend the hardi. With glass tile the bend at the bottom is gonna look like a neon sign.
You don’t want those gaps to be much larger than about 3/16″, 1/8″ is ideal.
roger,
i’m about to install a tiled shower with a fiberglass shower pan. i’m installing 1/2 in. hardiebacker. the problem is, the bathroom wall transition to the shower is 1 in. from the studs. that leaves me with another 1/2 in. after i put up the hardiebacker. what should i use so that i get the hardiebacker flush with the rest of the bathroom walls. hopefully, that makes sense.
Hi Binh,
Put an additional 1/2″ of wood over your wall studs before installing your hardi. You can use strips of hardi as your shims or 1/2″ drywall strips as long as your waterproofing goes between it and the tile.
just to be clear,
i could screw 1/2″ drywall strips to wall studs, then waterproof with 4mil plastic sheeting, and then put hardiebacker.
thanks brotha
Yup, that’s correct.
once i put up the hardiebacker, there is going to be a gap(a little less than 1/2″) between the shower flange and the back of the hardiebacker at the bottom due to the 1/2″ drywall strips. do i just fill in that gap with silicone caulk?
also, i am putting in an aquatic shower pan and the instructions say casting plaster/plaster of paris is MANDATORY as foundation. I’ve read reviews from people saying to steer away from plaster because it dries too fast. Can i use quickrete or mortar? If mortar, what kind?
i have wooden shims under the pan right now to make it level. once i put the mortar/plaster/quickrete down, will that help level it or will i still need to put wooden shims in.
thanks in advance roger!
Hey Binh,
Yes, seal up the bottom of your backer so no moisture can get up in there at all.
You need something beneath your shower pan to fully support all areas of it – it does not have to be plaster. I use cheap thinset. You can use cement, mortar, nearly anything really. Using a 50lb. bag of the cheapest thinset HD carries ($5 customblend) will work just fine. Once you get it poured and get your pan in there set some boxes of tile in it to weigh it down a bit and wait until the next day so the thinset is cured. You can level and move it around all you want before that to get everything where it needs to be. You can leave the shims in there, pull them out, whatever is easier for you.
I had my tub removed and someone came in tile the bathroom with a shower. For some reason the grout came up along the seams. Then it started leking into my bedroom under to floor. I found out it was backing up into the room. It did not do that anymore when I a towel down there it quit. Is it possible that because of grout missing. I am trying to figure out what to fix it. It was like a year half after it was installed.
Please help me. It put backer board down along with a shower pan.
Hi Angelique,
Not too sure what you mean by ‘along the seams’. Are you speaking of the grout lines, the corners, or…what? Offhand it sounds as if there was either no waterproofing (moisture barrier) placed behind the backerboard and the cumulative build-up of collected water finally overcame the ability of the board to retain the water and it began leaking. Or, depending on how your shower floor was constructed, there may just be a small leak which eventually built up and began leaking more significantly. Without very specific information about the construction of your shower I really can’t give you a more specific answer as to why your shower is leaking.
Hello,
Gota say your site is awesome… Finally someone that actually gives good advise without skipping any necessary steps. One question though. I’ve gotten all of my backerboad up and I’m just about ready to start taping… I’ve looked in a few stores and noticed there’s about 10 different options for mortars with a bunch of different additives etc for it. Any advise for what I need to tape the seams, then install 16 x 16 wall tiles in the shower?
Thanks
Hey Scot,
Any good modified mortar will work just fine. As a general rule the more expensive a mortar is the more flexibility it will have once cured. There are also some with aspects such as non-sag or sound control (for use on a floor over another living space) but generally just a good modified mortar such as versabond by custom (Home Depot) or any of the modified laticrete thinsets will work fine. I normally use Laticrete 253 Gold as my goto thinset. No need to get the liquid additives you include in unmodified when you can buy the kind with powdered polymers already added.
Sounds good… thanks for the help. One more question. I’m planning to install some glass accent tile along with the 16 X16 big tiles… Will the same stuff work as long as it’s in white?
Yes.
Shortest. Answer. Ever.
OK…. One more question. Getting ready to install the wall tile in the shower. What size trowel should I use for 16X16 tile? I’ve also heard about the 5-Spot method… is one more preferred?
Thanks a bunch!
Hey Scot,
The five-spot method should only be used on exterior vertical applications – not in a shower where an extreme amount of water would be able to penetrate the open cavities between the ‘spots’. So you want full coverage. I use a 3/8″ square-notch trowel for most of my installations.
I am working on 2 bathrooms have a shared wall with plumbing corner outside wall runs down long wall side of a tub and plumbing for that one shares corner outside wall where plumbing is for other bath tub shares side of tub inside wall.I had to rebuild shared wall and tub for master bathe is plumbing in outside wall and in corner of tha twall and center shared wall is plumbing for hall bath should i run vaper barrier along bouth outside bathroom walls and on bouth sides of center shared wall i have build in nook in that wall also it serves the master bath with jakusie tub shower and in the hall bath will be a slipper clawe foot tubshower.I have to shim abit in master bath backof bath area more than any where i am using hardie 1/2 ” backerboard would it be easier to do red gard verses vapier plastic due to having to shim what would you do?
Thank you
carol dawson
Hi Carol,
With that situation the redgard would definitely be a better choice.
Roger could I get away with using in the 6 “wall between two baths with nitch could i just use 6mi lvaper barrior onhall bath and master with nitch use also redgardjust for nitch area sticker shock is bad .butif thats whatihave to do i will .besure i understand you are talking obout redgaurd on boouth outside walls and bouth bath walls 6″shared also i was reading other post and one guy said his was behind studson outside wall on outside of studes is thick black tar bord and brick myhousebuilt in 70’s .Main goal is not have to do this again
Thank yo
Carol Dawson
jazzya@suddenlink.net
Hi Carol,
Yes, you can use either one or a combination – whichever you choose. The black ‘tar board’ is not going to make any difference on that outside wall, that is to shed water away from the wooden substrate of the outside of the house.
Roger, ok my nitch is made of 2x 6’s an question is doing wall board should wall board on back side of ittch could be the wall for other bathe .nitche will open faceing master inside wall board should it come out even over the wall board that comes from bottom of tub wall ,or even with wall board inside edge or outer edge hope i am making sence to you.also should the gap between the backand sides be 1 16th,3 16th or ?
Thanks again
carol dawson
Hi Carol,
Yes, the back of the niche can be the wall of the adjacent shower. The inside board should be flush with the plane of the wall in the shower it is on (the board that comes from the bottom of the tub wall. The gaps should be between 1/16″ and 1/8″.
Hello Mr. Elf,
We are installing the Hardie backerboard to tile our shower. We have a transition where the HBB and drywall meet. The gap is going to be about 1/16″ but there are going to be some gaps that are more than that. Do we just use the thinset and tape it up? We thinset, then tape, then thinset over that again, correct? This is in the shower, and the edge of the tile will go over the transition. Is this correct? I heard we should use a non hardening caulk (butyl rubber) or something like that for the gaps between the drywall and HBB.
thanks for everything.
Hey Lefty,
Everything you’ve stated is correct except the caulk. Just fill it with thinset, tape over it, then skim it smooth with more thinset. Yes, tile can go over that transition. You can also paint over any of the area if you need to.
Thanks Elf! I have an older Makita power drill, and might be on the outs. What cordless drill do you recommend? I am hoping I don’t have to buy a new one, but I probably will have to. I’m an average homeowner, with average projects. Budget is no more than $300 on the very high end. The less money on a good drill I can spend, the better.
Thanks!
Hey Lefty,
I’m a DeWalt whore!
I absolutely love their cordless drills and the new XRP series keeps going for quite a while during my day. Average projects shouldn’t even make it blink. You can usually pick one up around 200 – 225 during one of Amazon’s specials or check Home Depot’s clearance items. I usually see at least one or two a month there under a couple hundred dollars.
Hey roger, I’m putting up the backerboard now was wondering about countersinking the scews. I got the special screws by hardi, and either my drill needs to do some pushups or the studs need some muscle relaxers, cause I’m def not countersinking all the way. Do I need to keep at it and make sure they are or will it be ok? …and you recommend silicone over all screw holes right? every time I go get materials for the next step, I enjoy questioning the workers on what I’m doing. I’ve found one outta probably 10 that follow what you say. Kinda scary…thanks for your help.
Kreston
Hi Kreston,
One out of ten – that’s pretty good actually.
The more you can countersink those screws the better. You don’t want one that is going to cause any of the tile to not set flush with the ones next to it. I only recommend silicone over screws if you are using a topically waterproofed board such as denshield. If it’s just a vapor barrier with backer over it or you are using a different topical membrane such as kerdi or redgard you don’t need to silicone the screws.
Ok so this probably is a really stupid question, but if the backer board stops just above the lip of the tub and there is nothing behind the tile, won’t that allow the grout to potentially break apart between the tiles?
Hi ML,
Not a stupid question at all. The grout will not crack or break apart unless there is undue movement. And you don’t walk on that part of the shower.
It’ll be fine.
Had a plumber visit today to replace a busted pipe from the kitchen sink. Supposedly a good plumber, whatever that means. Yes, he saw my butt naked bathroom so chimed in that he also does that kind of work. Well, since you know how I like to pick everyone’s brain so asked him how he puts up the dang hardiebacker boards and yesssssssssss, Roger, he butts them against eachother. Why the heck does Hardiebacker even bother to put out those nice in color pamphlets, bilingual, in which it says on their in black and white to leave a gap if no one even bothers to read them. Disgusting. Even more disgusting than what the plumber is charging to replace the pipe. Well, maybe not as disgusting because the quote was quite disgusting. I want a niece or nephew of mine to become a plumber. Don’t need anymore teachers or doctors or nurses. We need a plumber in the family. Yes, I know, all off topic. Here, I’ll do it to myself
Ceci
Hey Roger,
The mud bed is in and, in most places, the backerboard packed in good and tight. But in 2 corners where the studs were notched for the pan liner, the backerboard has a little (1/16″) give at the bottom when you push on it. Is this something to be concerned about?
And if I have some low spots in the mud bed, can I just fill them with some thinset to make the floor flat, (not level!)?
Thanks for all your help.
Ed
Hey Ed,
Nothing to worry about at all. Once the tile is in it will stiffen the entire wall more than enough. Yes, you can use thinset to fill in low spots.
Hi, question regarding installing the tile over the backerboard. Im concerned over the bottom row since you stated to (stop the backerboard about 1/8 inch above the lip) so does the first row of tile go partially over the lip of the shower pan and part on the backerboard? If so wont there be a 1/8 ” gap behind the tile that will have no water proofing ?
Hey Terry,
Yes, the bottom portion of the tile (maybe 1″) will not be attached to anything. Your waterproofing, however, needs to either run down behind the backer and over the front of the tub lip (traditional method) or a bead of silicone is placed between the bottom of the backer and the tub and your topical membrane (liquid or sheet) is placed all the way down to the tub. There should be absolutely no gap in your waterproofing from the wall to the tub.
If i install 4 ml plastic on the studs and use redguard over the cement board will moisture be traped between tme them. If so which one is better to use.
Hi David,
Yes, that will trap moisture. The redgard (or any topical membrane) is always the better option for a shower since the waterproofing is directly beneath your tile rather than behind a substrate. It keeps all the water out of the substrate.
Oh, Roger, I just looked at the date of David’s post. Hmmmmmmmmmmmmm, that is today. So are my questions that complicated that they get thrown to the bottom of the pile? (Insert big smiley face)
Ceci
Yes, more questions and since you and Sparky are practically saints expect the usual cheery response. I know you say to inbed thinset between those gaps of the Hardiebacker boards that are on the same plane and then inbed tape and then more thinset over it, but I just can’t see how all that stuff(the tape is 2 inches wide) will fit in a gap of 1/8 to 1/16 inches wide. Does one cut the tape to let’s say 1 inch to squish it in?
Ceci
The tape is not imbedded into the gap itself. The thinset fills the gaps then the tape is laid flat bridging the gap of the boards, then thinset is layered over it to flatten it out.
Well, I am glad that got cleared up. Would have looked kind of silly if I insisted on something that isn’t physical possible.
Thanks for clarifying,
Ceci
Roger,
I hope to do a better job constructing my bath renovation than I did my question. Or perhaps I should try to ensure that my future questions arrive so that you might stumble upon them before stumbling upon your third beer or maybe compound questions should be reserved for cross examinations on TV attorney shows.
To an old dru–, er, pro such as yourself, it must have seemed like the” the inane question of the day”. Let’s see, lay the board in wet thinset OR just wait till the thinset hardens and then lay the board?
A no-brainer, maybe so but to a novice, still a question.
My concern is, after setting the board in the “wet” thinset, do I screw it down while wet and risk changing its attitude relevant to its neighboring pieces or wait until set and then install screws.
DUH!!!!!
Thanks, Ron
Hey Ron,
Actually I’ve answered that exact question – the way you asked it earlier, at least four times that I can remember off the top of my head. So no, I didn’t even give it a second though.
It depends on how bad your subfloor is. If it is extremely off – not flat at all – you can wait until the thinset cures before screwing it down. Either way works fine and I’ve done it both. If the board will be pushed toward the floor while screwing it down it would be best to wait and let the thinset cure first.
Hello Roger,
I have two different installations to ask about:
1. Am about to install cement board on a plywood substrate, will set with mastic(thinset) and then screw to plywood avoiding the joists that the plywood is screwed to as you previously advised. Do I wait until the mastic/thinset cures before screwing the cement board to the plywood or set screws as I install? This is a non wet area.
2. Will remove existing tile from tub surround and retile same. It appears that the existing tile is adhered to sheetrock. I intend to install cement board as described above, studs, vapor barrier, cement board with gaped and taped joints. Do I now need to waterproof the cement board or rely on the plastic vapor barrier between cement board and studs, keeping in mind screws mounting cement board will penetrate the plastic.
Thanks, Ron
Hey Ron,
1. Nope, lay the board in the thinset while it is wet. This will allow the thinset to conform to the bottom of the board and the floor and, once cured, will fully support the board.
2. The vapor barrier is your waterproofing. Yes, the screws go through it, but the screw also creates a ‘pucker’ of the plastic around it. when water runs down the wall, behind the tile, it will run around the screw rather than getting into your wall cavity.
Hi Roger,
so I’m going to start cutting tile to install today.. this is a shower/bath installation where I’m also tiling a tub apron, and a narrow section of the wall up from the floor next to the shower (the new tiles will meet some other tiles that I left on the wall, since I was only interested in making a waterproof shower installation, not in re-tiling the entire bathroom).
The problem is that the short section of wall coming up from the floor next to the bath is not exactly one subway tile wide (its around 4″ wide and the tiles are 6″). Although I’m “staggering” the tiles for the rest of the installation, I’m planning to fill the gap up from the floor with 5 tiles cut to 4″ (with no staggering pattern); do you think this will look weird?
second problem… is it better to start placing full tiles around the top of the bath , then work down to the floor and place a cut tile at the floor, or would you start tiling at the floor and move up, with the risk of having to have cut tiles all around the wall/bath join? I’m inclined towards option 1 since part of the tile around the bath will not be supported by cement board (there is a gap there of around 1/2 inch), but I wondered what your take was.
There is another option which is to optimize placement of all the tiles by installing a row of thinner highlight tiles at a point close to the edge of the tub apron, to space out the subway tiles correctly.. I guess my question is which option sounds the most professional!!
Dont know if I’ve described the situation clearly.. anyway let me know what you think and thanks again for all your help!
Hey Colin,
If your tiles are 3×6 subway I would turn them 90 degrees and run them up the wall in that direction – going out 3″ rather than 4″. The offset grout lines on every other tile finish off the wall better than running all the grout line all the way through to the edge and just stopping – that tends to look unfinished. Start with a full tile at the tub then work down to the floor, make your cut down below the tub where it meets whatever you have down there.
hey roger,
just to be clear, so you are suggesting running a row of tiles vertically up the wall at the edge of the installation, to make a border essentially? sounds like a good idea if so. I was planning to install a border tile (a rounded pencil) up the edge, but I could do that as well.
BTW much enjoying your tweets – righteous stuff!
cheers – colin
Didn’t know you had the pencil rail, that will work also. I’ve done the vertical subway tiles for an edge and it does give it a nice framed, finished look and keeps all the tile the same. Whichever you like is the right one.
My twitter feed is fairly mild, actually. If you want the one where I rant about politics with no holds barred just DM me on twitter and I’ll send it to you. If you like my latest tweets @FloorElf you’ll probably love the other one.
Great site! I just bought all my supplies and was planning on getting started tonight. At Home Depot, the guy told me that I don’t need thinset for the joints (which I was THRILLED to hear). He said to apply the redguard on the joints, then use the mesh tape over them. Once dried, then I can apply a coating of redguard on the entire cement boards. I did ask about thinset, but he insisted it wasn’t necessary. While the whole waterproofing thing scares me, I live in Las Vegas, and we don’t have many mold problems. Was this horrible advice or should it work ok?? Thanks in advance.
Hey Scott,
Unfortunately that was incorrect advice. He is confusing two entirely different aspects of the substrate. The tape and thinset on the seams has nothing to do with the waterproofing. What it does is create one large monolithic structure (wall) which will all move in the same direction at the same rate. Not taping and thinsetting the seams allows each individual board to expand and contract in different directions independently. It needs to be done. Really.
Sorry.
Thanks Roger… it sounded a bit too good (and to easy) to be true. Bigger problems though… our existing shower pan cracked when I was installing my first cement backerboard…. I quit that night and ordered a pizza instead…
Roger I have three questions: 1) once I install the cement board on the shower walls will that be level enough to install porcelain tile? and 2) I will be installing 12×12 porcelain tiles in my shower so do I need to use the 4×4 curved base tiles before tiling the rest of the shower? 3) will the laying of cement board on the entire bathroom floor save me some leveling headaches before I install the tile?
Hey Anthony,
1. If you shim out the cement board to level as you install it then yes, it will be level enough.
2. You don’t need to use the curved base tiles at all. If you are going to use them then yes, you need to install them first then stack the larger wall tile up from them.
3. Only if you install the thinset beneath the cement boards so that the floor is level.
Cement board will follow the contour of whatever you install it to – wall studs or the floor. You need to fully support any areas that need to be either higher or away from the studs. You need to compensate for the substrate to make your cement board level and flat. The flatter your cement board the easier your tile will be to install. It’s all in the prep work.