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 have installed a fiberglass shower pan & install insulation with a vapor barrier, but i am confused aboutthe correct method to set the backer board . do i go above the shower pan or do i set it on the lip that goes around the entire pan. then do i set the first row even with that lip or go above with a straight edge to
set the second row working my way up the wall.
Hey James,
The backer can either go right to the top of the flange (with a 1/16″ gap between the backer and flange) or you can shim out the studs so the backer can run down over the face of the flange to within about 1/16″ from the horizontal arm on the tub.
I normally begin with the very bottom row with a 1/16″ spacer between the tile and the horizontal arm on the tub and stack the tile up the wall from there. As long as you have the spacers supporting that bottom row you can stack it to the ceiling if you want. The gap between the tile and pan is siliconed when you’re done.
Roger,
I am installing backerboard (BB) in place of drywall on a wall that will be a fully tiled (membrane) shower, but the final floor height is not yet known. Can I run the BB to, say, 1/2″ off the subfloor (slab), or do I have to guess where my preslope mortar base will end up and leave a gap above that?
Thanks.
Craig
Hi Craig,
It depends on what type of membrane you’ll be using. If you’re using a traditional liner on the floor it needs to run up behind the walls, so that will need to be in place first. If you’re using a traditional vapor or moisture barrier behind the walls that needs to run over the face of the liner on the floor – so it still needs to be in place first. If you’re using a topical membrane on the floor and a traditional membrane on the walls you need to rethink your shower construction – that won’t work.
If you are using a topical membrane for everything then you can install the walls down to whatever point you want and build your mud deck right against it.
So yes, you can install your BB as you’ve described provided you are using a topical membrane on the floor. If not, the liner over the preslope needs to be installed first.
The term ‘membrane’ incorporates a lot of different products.
Thanks Roger
I like to enjoy my chocolate milk with sand between my toes, so am planning for a fully tropical, I mean, *topical* membrane install.
Thanks Roger. I hope the elf finds his ostrich.
Craig
Roger, I agree with all the other positive comments about your site and information. You give the most clear and easy to understand instructions and it just so happens exactly what I needed to know. Instead of staring at studs for another week I can progress to moisture barrier, hardibacker board and beyond. Thanks! Gary
You’re very welcome Gary. Now get to work!
Roger…great site…I have already installed most of the backer-board around tub/shower (remodeling existing tile)…did fair amount of reading before starting, but failed to see anything dealing with leaving a 1/8 inch gap between top of curved up lip on tub and first piece of backer board. Of course there will still bel plenty of space for tub caulking under the first row of tile, but I know that the issue is tub “movement” after all is done…Is this situation where I could feel OK about moving forward or should I start all over?…Factor in the wife’s patience…Thanks, Bruce
Hey Bruce,
Go ahead and finish it up. Before you silicone the tile fill the tub with water. This will allow the silicone to be a full, relaxed bead when the tub is being used (most movement) and compressed when not in use. It gives a tighter seal.
If we want to protect the studs behind the moisture barrier and hardibacker board. why not cover them with something like Thompsons Water seal before putting the moisture barrier on?
Hey Gary,
No reason not to if it will help you sleep at night.
JUst a question about the wall to ceiling corners. Do I just silicone the interface or should I mud and tape the corner as well? I’ve not decided yet if I want to tile all the way to the ceiling or only about 7′ up. Am definitely not tiling on the ceiling though.
Thanks for your site, it has been a great help while building my shower.
Hey Dan,
If you are not tiling the ceiling then tape and mud it.
Your writing style and clear, concise instructions are beyond a breath of fresh air. Thank you!!!
Our bathroom remodel is still largely a twinkle in our eyes, but just last week we had some framing done for a small expansion where our tile shower stall will be. There is a portion of one wall where our builder was planing on using plywood to compensate for the deficit between his new framing (with modern 2x4s) and the old framing of a weight-bearing wall (old hand-carved 2x4s that are actually 2″x4″).
Hardieboard is the material I would like to use as a backer for our tile, so what do you recommend that our builder use to level this old+new plane if not plywood?
Hiya Kate,
He can use the plywood if he wants, he just needs to cut it into 1 1/2″ strips and attach them to the face of the new studs to bump them out onto the plane with the existing 2×4’s. You do not want a solid layer of plywood behind your backer, but the strips on the face of the studs are fine.
Ok great. Our guy is admittedly inexperienced with tile prep, but his basic framing looks good. I’ll be going over some of your tips and suggestions with him soon.
I have one more question that about glass blocks and backer board.
I’m assuming that backer board should be extended beneath/behind any glass block matrix that I install as a wall of my shower stall?
I’m looking at using glass blocks to build one wall our custom tile shower. The problem is that around 4 feet up from the floor, the wall takes an approximately 45 degree angle on the underside of a staircase. Here (http://www.flickr.com/photos/kate-and-shay/7270139314) is a really bad picture where you can barely see the bottom of the slant. The area where I plan to put a glass block wall would cross over at about the mid length of the old tub depression.
Assuming the angles work out, am I likely to be able find triangular glass blocks like these (http://www.score.com.hk/glass/triangular.htm) in the US? That’s the only site or picture that I could find for them so far. Not that I’m necessarily opposed to ordering something from Hong Kong, but would prefer something a bit more local.
Another concern is how best to make sure that the seam between the long edges of the triangular pieces and the sloped ceiling/wall is solid for wall support and that it won’t allow water from the shower where water shouldn’t be.
I think the angles will be close enough to work with if I can get blocks like those pictured, which will be at least a silver lining to the cloud that is our very steep staircase.
But…if the angle of our staircase slant is not 45 degrees or I can’t find triangular blocks, could I bring a step pattern like this (http://www.lifeofanarchitect.com/wp-content/uploads/2010/03/triangle-bath-glass-block.jpg) as close as possible and fill the gaps with something else? What something else would you suggest?
Thanks in advance!
Sorry, guess that’s more than ‘one more question’
I have never seen those glass blocks. Doesn’t mean you can’t find them here, just means I never have. The architecture photo you linked to is the only viable solution I’ve seen for a 45 degree wall and glass blocks. You could always build a solid wall there (frame, actually) and have the center of it open to accept the blocks in the correct size. The shower side of that wall could be tiled right up to the glass.
Any waterproofing you have in your shower will need to run under the glass as well. The joint is siliconed after the glass is installed. As long as your substrate is properly waterproofed and you have your glass siliconed around the perimeter you’re not going to have any problems with it.
Framing the wall and filling it with glass blocks may work. I’ll play with that a bit too. We’re trying to get some ambient light through that wall as the rest of the shower will be pretty much a dark cave.
Thanks again! Will certainly be picking up some of your publications.
I’m curious about not mudding the corners to allow movement of the walls. Won’t this lead to cracking of the tile grout corners with this movement? Many websites say to mud the corners. It seemsd to me that mudding trhe corners would prevent cracking of the grout along the tile corners. Not sure what to do here, help.
Hi Gary,
First thing first – corners and changes of plane do not get grout – they get silicone. Grout will crack whether you silicone the corners, mud the corners, or fill the corners with epoxy – makes no difference.
When two walls of different orientation meet at the corner it causes a stress area in your substrate. The walls are going to move in different directions, regardless of what you do to prevent it. This movement is going to cause the two different planes to move in different directions, either toward or away from one another to some degree. This causes a stress point at the corner. Any cement-based product, be it mud, grout or anything else, is going to crack. It’s a fact of life.
All layers of your corners should compensate for this movement in some manner. The best is silicone. It will fill the corner, yet allow this movement to take its course without causing this pressure to find a release point. You are creating a place for the stress to dissipate. If you don’t do that, it will find its own place to dissipate – normally somewhere in your tile installation.
If you utilize flexible sealant in the corners you compensate for movement which is going to occur. The more you can control and channel the stresses where you want them, the less they will do so by themselves and cause problems in a visible manner (cracking tile or grout, bond loss on tile, etc.).
That said, there are always more ways to do something than mine – I know that. I recommend, to the best of my ability, approved methods set forth by the TCNA. It doesn’t mean other ways don’t or won’t work, it just means that it’s an approved method and the one I normally utilize.
Thanks for the quick reply and being such a great resource.
Roger,
My Americast tub instructions call for the cement board to overlap the tub flange and hang an 1/8th of an inch off the tub deck. You seem to suggest hanging the cbu above the flange all together. Did I miss something? I have the cbu over the flange now and have shimmed walls out enough to provide for a flat surface… Should I pull it all all off and redo? Or is it a matter of ease/preference? Lemme know. Want to tile Saturday.
Hi Bill,
WHOA!!!
I only suggest the backer above the flange as one option. The other, and technically correct, option is exactly what you have there. Provided your walls are flat that means you’ve done it correctly and you’re good to go. Now get to work!
Thanks Roger… I’m on it boss!
Great article! I have a few (ok, many) questions though….
1. I just finished putting silicone caulking in between all my cement board gaps…I was afraid water was going to get in where the gaps were rather larger (about 1/4″), and I hadn’t found your article yet. The paragraph on “allow for movement” makes me worried, because some of our cement boards are right up against each other, and the others are now filled in with silicone. I put alkali resistant mesh tape on all the seams and was going to cover them with tile adhesive when the silicone dried to further fill in the gaps – or should I just leave the silicone? If I should fill in the seams, is it ok to use tile adhesive or should I get thinset mortar? I was going to use tile adhesive for the tiles rather than mortar. If you recommend thinset for the seams, what kind? There are so many at Lowe’s that it is really confusing.
2. There is a bit of a gap (maybe 1/2″) between the bottom most cement board and the shower floor. Should I fill it in with something?
Thanks so much!!
Hi Candace,
First thing first – get rid of the adhesive. What you have there is mastic and has no place whatsoever in a shower. You need to use thinset for anything inside your shower.
As far as your seams – The gaps in the corners (changes of plane) need to be filled with silicone. Any gaps on the same wall between sheets need to be filled with thinset, taped, and skim-coated with thinset. If you have silicone in any of those you need to remove it. If you have any changes of plane without gaps you need to get a gap in there by either cutting it out or removing and replacing the board in the proper position.
If you have a tiled shower floor you need to tape and mud that seam. If you have a pre-formed base you can either fill it with silicone or just leave it (provided your waterproofing membrane is installed and lapped correctly.
Roger,
Thank you for sharing your expertise!
I have a question about the final step – filling in the gaps with thinset and tape. I filled the gaps with thinset this morning and it set. Now that I’m looking I see I didn’t include the tape with the thinset. Can I sand and do this step again? Adding the tape now seems like it will make the surface bumpy. Can I proceed without taping?
Thanks, again!
Hi Karen,
Yes, you can sand it down to the surface and apply the tape and more thinset. The tape should have been done at the same time, but you can still do it. You CAN proceed without taping, entirely up to you. Your shower won’t blow up
but taping and thinsetting the seams creates a monolithic surface.
Thanks! Now that the weekend is here – it’s back to work on the shower project. I will go ahead and sand it down and redo the final step before I begin installing tile. Better to do it right – even if it takes 2 tries!
Thanks again.
what would be the max gap I should try to fill in my NOT so square shower between cement board?
P.S. I love your site!
Hey Bryant,
I’m not sure I understand whether you mean fill with more backerboard, fill with thinset and tape, or fill with silicone. Any gap over 1″ or so should be cut back to the next stud and a piece filled in large enough so that gap no longer exists. Any gap under 1″ can be thinsetted and taped if the pieces are on the same wall (plane), although it should be under 1/2″ ideally. Any gap in the corners should be less than 1/4″, if more than that see the first solution.
Thanks roger! I was meaning with thinset and tape. The problem is between two pieces of backerboard on the same plane. Do to a mistake on my part, I have a 3/4″ gap on one end and a 1/4″ gap on the other. As with most projects the budget is tight and I didn’t want to cut another piece. (Wife might burst into flames)
Aaah, you can tape and mud that. Wife’s gonna burst into flames about something, may as well give her a reason, eh?
Hi Roger,
I am redoing my shower using a swan stone shower base. My question is, if I want to use tile on the walls, how much of a gap I need to leave between the cement board and the lip of the shower? Instructions from sawn stone say to leave a gap of 1/2″ between cement board and the lip of the shower, if using swans tone wall, but I’m thinking that this gap will be too large if I’m using ceramic tile . Could you please advise about it?
Thanks
Hi Myriam,
1/8″ is fine. I don’t know why they recommend that much, it’s a LOT. Dunno what they expect you to do with a 1/2″ gap.
Hi. I have a 3 wall stand up shower and the hardiback up. There is a small gap from the cement boards along the top and sides where it meets the sheetrock. Can I silicone it? I’ll be tiling and the tiles will slightly overlap the sheetrock. Can I use the thin set over the silicone when tiling? Thanks so much!!
Hi Sara,
Yes, you can silicone all the corners. The transition from the backer to the drywall should be taped and mudded with alkali-resistant mesh tape and thinset. The thinset will not stick to the silicone, but it doesn’t need to.
Hi Roger,
Do I silicone the corners and also where the hardie meets tub before I tile or at the very end?
Thanks,
Gwen
Hi Gwen,
Yes, silicone all changes of plane and where the wall meets the tub to prevent thinset from entering those areas.
I am installing a shower stall where one of the walls is an existing outside wall
that is covered with plywood. The plywood cannot be removed. In a previous post
you indicated that placing hardibacker on top of plywood creates a problem.
I have the option of not covering the other two walls with plywood. Are there any
additional precaution I can take beside not using plywood on the other walls?
Thanks RR
Hey Ron,
Nope, that’s about the only thing you can do. If you could make some relief cuts in the plywood on the wall before installing the hardi over it that would go a long way toward compensating for movement and eliminating problems.
Hey Mori,
You can use either.
Does the plastic sheet have to be one piece? I ended up cutting 6 additional inches of drywall so the plastic sheet doesn’t go all the way down to the tub.
Hey Mori,
As long as the sheets on top overlap the sheets on the bottom it’s fine. Just overlap them like roof shingles.
Thanks
Roger, thanks again for the quick reply. It’s too late for us to correct what we’ve done wrong but we do have a second bath we’re going to do so maybe we’ll get the process correct next time
If I’m dissecting all the instructions and comments here correctly I would surmise that When using Hardi backer board around a tub surround : 1. Do not use a vapor barrier behind it IF you are smearing it with a waterproofing coat (ie Red Guard) 2. When screwing up the boards they are going to be independent on each wall. They are not going to be tapped together and mudded. 3. BEFORE tiling, caulk the corners (changes of plane) everywhere and at the gap between the tub and the Hardi. You do not even have the Hardi going over the indented lip in the cast iron tub, you have it suspended above it – then you caulk it and Red Guard it.
Hopefully with our 50 year old house the settling is about done (at least for the next 10 years we’re here).
Did I get all that right?
Of course the way we did it is a bit off from this
Thanks,
Susan
Hey Susan,
You got it all right! Whaddya need me for?
Hi Roger,
I’m trying to re do my shower. I removed 1/2 in. drywall from two of my three shower walls. On the third wall I removed 1/2 in. drywall and some kind of fibrous board that also 1/2 in. I’m going to add 1/2 in. plywood strips to these studs to because I only plan to put up the 1/2 in. cement board. Should I put a 1/2 in. strip in the corner where the second and this third wall met? Also, how much of a gap should I leave between the cement board and the drywall?
Hey Mori,
Yes, you should shim out the stud in the corner as well. You need about a 1/8″ gap between the backer and drywall. Tape and mud it with thinset. You can paint over thinset if you need to when you’re done.
Thanks for the reply. One more question. Do I need to put up any additional framing at the top of my shower? I only tore out the tiles and a little of the drywall at the top of the shower but the frame is at the top of the wall.
Nope, no need for additional framing as long as you have 16″ o.c. studs it’ll be fine. You can add more if you feel uncertain about it, though, it never hurts.
Hi Roger I installed a kbrs base in my shower. I also built out the walls with plywood to allow for the i/8 gap away from the flange for the durock. Should I put a vapor barrier over the plywod and the install the durock and the kbrs also has shower seal and tape for the joint at the base and roll the remaining waterproof on the rest of the walls of the shower. just to be clear I shoud not thinset any corner just silicone them
Hi Nick,
If you bump out your walls with plywood it needs to only be along the face of the studs – not behind the entire wall. In other words you should not cover the entire wall with plywood then go over that with backer. That will create a lot of stress on your substrate because the entire wall will expand and contract with normal seasonal movements as well as being affected by the humidity changes in a shower. It will create problems. You can rip strips of plywood and install them onto the face of the studs and go over them, but not the entire wall.
You should install the pan first, then run the backer down to the top of the pan. This way the backer hangs over the pan. No thinset in the corners – just silicone.
Hi Roger I removed the ply wood and cut it into 4 inch strips and installed them horizontal across the studs leaving 10 to 12 inches between. Should I install a vapor barrier before I install the durock and on the outside wall that has insulation should I replace it with non faced if I install a vapor barrier on the outside wall as well
Hey Nick,
Sorry, I meant down the face of the studs – no big deal, though. Just make sure you mark where your shims are so you don’t miss them with your fasteners.
You can leave the insulation as it is. The cavity between the two barriers will be open and not sealed up so vapor can dissipate – it won’t be a problem.
Hi Roger thanks for the information. The wall with the faced insulation is not being furred out so the plastic will be right on it, I was going to remove the paper so only the plastic would be there or should I bother.
I wouldn’t even bother. It’s not going to hurt anything or cause any problems with the plastic right against the paper.
Roger,
Thanks for all the help you provide. One comment I have is that I find it slightly confusing to leave a gap “for expansion” around the backer board and yet you mud and tape it to make a “monolith”. Seems to me you can’t have it both ways.
Andrew S.
Hi Andrew,
You’re correct, and I’ve been meaning to change this. The gaps at the changes of plane are not taped and mudded, they are filled with silicone or simply left open to allow for movement in different planes. The gaps in the same plane (between sheets on the same wall) are taped and mudded so the individual sheets do not move independently.
Thank you!
Hi Roger,
I am getting ready to mud and tape my seams on my tub surround. It makes sense to me to not mud and tape the corners, but use silicone instead. I have read for hours on the interwebs what to do with the corners. I swear, the only place that does not advocate mudding and taping corners is right here. Siliconing the corner joints in between the tile allows for the movement of the intersecting planes, but isn’t mudding and taping the backer board corners a waste of time?
Hi Matt,
The reason for mudding and taping the seams is so the entire wall will move the same amount in the same direction. If you don’t the individual boards may move separately and cause undue stress on the tile installed over it. You want the entire wall to move as one.
Hi Roger!
Thanks for this website, it’s really helpful. I have a two-part question:
1) If I’m using Redgard as my moisture barrier, I don’t need to use any kind of backing between the studs and the cement board, correct?
and
2) What do I do for blocking moisture in the gap I am supposed to leave between the lip of the tub and the cement board? Silicone caulk?
Thanks so much!
Hi Dashel,
1. Correct
2. Yes, use silicone between the backer and base, then paint redgard right over it.
Roger,
We are re doing our shower, put the cement board up and taped all seams with thin set and then waterproofed it with a liquid don’t remember the name. anyway now it is a bit uneven and am wondering if it will be ok to tile over. Do we just adjust this with the thin set when tiling?
Hi Marie,
Yes, you can compensate for out-of-flat walls with thinset up to 1/4″ if necessary, if it’s less than 1/8″ or so it’ll be easy.
I have a small leak around my shower valve after installing the hardibacker …it’s also been taped and mortared. I have access to the leak but can’t get a wrench in there to tighten it. Is there something I can use to stop the leak.
There may be a tool for that, I simply don’t know Steve. You may want to ask the fine folks over at Terry Love’s plumbing forum. They may tell you to just take out a tile, if that’s the case come on back here with any questions you may have.