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.
Hi Roger, I am reinstalling the shower floor tile on the mortar shower pan 3 by 4 ft. and just the bottom row 6 by 8 inch tile. The shower has 4 inch concrete drop with a 2 by 4 on it where I need to put my 6inch wall tile. I bought Densguard tile backer to put before the tile. I can use a tile backer or deck screw in the 2 by 4 but is it ok to put tapcon screws in the 4 inch concrete part of it? By the way the backer board on the wall looks like wonder board with no plastic or roof felt behind it. It doesn’t look like any water proof paint on the front of the wonder board either. The wonder board was sitting on 3/4 by 4 inch possibly thinset? up against the 4inch concrete wall.
You can use tapcons if you need to but do not screw anything below 3 inches above the top of the curb (or the floor from which it drops). I’m assuming here that you have a waterproof liner in the shower floor? I hope?
Hi Roger,
My husband has been working his butt off redoing my sisters bath. He has all the hardibacker board up and we are going to use the Redgard to waterproof it all. I just found your site today and wow I wish we had found it a week ago. We have 2 questions for you. First, my husband left about 3/8 inch gap between the bottom of the backerboard and the horizontal lip of the tub. How can we fix that problem? 2nd question, how do you waterproof a window in the shower? Can we use hardiboard and then redgard it , then tile it at a slight slant?
You are so amazing… thank you for all this great information.
Please help before my husband kills me for offering him up to redo her bath.
Melinda
Hi Melinda,
Ideally the backer should be taken down and lowered to the proper height. Alternatively you can silicone that gap – but that’s a lot of silicone. The window can have hardi installed to it and silicone between the hardi and window frame, then redgard everything. Make sure the sill is sloped a bit toward the inside of the shower.
Thank you Roger! We will take down the backer and lower it to the proger height. One more question if you don’t mind. My husband used 1/2 “drywall behind the backer on one wall to fir it out. I just read you don’t recomend this. If he seals the backer with Redgard will the drywall still be a bad idea?
Thanks again for your help.
Melinda
What exactly is the “lip “of the tub? Is it the little edge that screws to the studs, or the top of the tub?
Most commonly the lip is the 1 – 1 1/2″ vertical flange at the very top of the tub which is attached to the studs.
Naw, if you have a topical membrane don’t worry about it, it’ll be fine. (don’t tell the tile police I said that
)
Hi Roger, I ussually never ask for suggestions from someone I don’t know but I can tell you really know ur stuff here.
I’m attempting to create a steam shower in my basement. Plumber roughed in the drains and water with 40mil liner, with very good workmanship. I framed a seat with a pitch and did 4mil vapor barrier on walls, had some liner left over so I lined the ceiling with it before durocking ceiling. Almost done with the cement board…planning to siliconing the joints then using the goof proof kit for the mud job. Any suggestions would be greatly appreciated. Thanks
Hi Matty,
Steam showers are completely different animals and EVERY one is different. You can download the basics here: Laticrete steam shower manual. Sounds like you have a good solid base started, though.
Hi Roger, great website!
I have a question about the traditional waterproofing method you describe.
When I put 6 mil poly behind wonderboard and screw it down every 6 inches as per manufacturer’s instructions, what keeps the water that soaks the backer board from penetrating through the screw holes through the poly into the studs?
The only way I could think of was to pre-drill all the holes for the backer board and load them with silicone before driving the screw which seems like a big pain in the ass.
Thanks for your time!
Hey Matt,
Do not pre-drill the holes – it is a pain in the ass. As you screw the fastener in it will cause the poly to pucker around the screw. As you tighten the backer it will cause this pucker to be sandwiched between the backer and stud. This creates a ‘dam’ of sorts which will cause the water to run around it rather than into the penetration.
I plan to use CEG-Lite epoxy grout and the matching color (earth) Polyblend sanded caulk. The grout claims to never need sealing. I love this idea but, is it really realistic? I wanted to avoid sealing if possible.I’m also asking for your personal opinion on whether to use the earth color everywhere caulk is needed or white where tile meets tub? I know it’s a personal preference but wondered which way you prefer. Thanks for helping me along the way, the job turned out nice and I feel good about the waterproofing I’ve done!
Thanks again,
Deb
i just visualized the corners at the tub and pictured earth colored grout meeting white…not good huh?
Deb
Hi Debra,
Yes, the urethane grout does what it says. It does require extra curing time before water exposure, so just keep that in mind.
I prefer the colored silicone against the white tub. Reason being that putting white there, the white tends to not have a nice clean line – goes into the grout lines, etc. If you use the colored you’ll still have the color change (which you’ll have anyway) but you can get a nice clean line against the tub.
Hi Roger,
I’m getting ready to tile a stand-alone shower in my basement. My contractor already installed a cast iron shower pan and Durock 1/4 inch cement board, and everything looks ready to go. However, upon reading USG’s cement board installation manual, USG stated that 1/4 inch cement board was not to be used for wall applications, but instead only for floor and countertop use. My contractor did a very thorough and professional job throughout my entire basement, so I can’t understand them making an error like this. Will the 1/4 inch backerboard not support the weight of the tiles?
Hey Brian,
It will support the weight of the tile just fine (unless it’s on the ceiling). The problem is with the sturdiness of the board between 16″ o.c. studs, it simply isn’t very stable. That said, it may be just fine. I would bring up your concerns with your contractor and find out why he chose the 1/4″. There may very well be a reason for it (likely to help the backer meet flush with another wall). I have done it a few times for various reasons, it will be fine provided it is constructed properly.
Hi Roger,
I have my hardiboard up, seams taped and mudded and now I’m ready to apply redgard. But I have two questions: first, when we were mudding the drywall and spraying texture, despite my best efforts, some drywall mud got on the hardiboard. I scrubbed the hell out it with water and most of it came off, but will this be an issue with the redgard sticking? Secondly, the tile we selected for the tub surround is 8″ x 12″ Brazilian slate porcelain floor and wall tile with a rough texture meant to emulate the look of natural stone. Is that a good idea to use a rough texture for tub tile? I’m starting to have second thoughts.. thinking it will be hard to keep clean. Do you have any experience using rough textured tile in this setting? Thanks so much for your help.
Jeremy
Hey Jeremy,
The residue from the wall texture won’t be a problem provided it’s not ‘dusty’ and the amount left is ‘in’ the backer or wall rather than ‘on’ it.
I have installed rough textured tile in showers. It is a bit more difficult to keep clean, but not considerably so. Being a porcelain it shouldn’t be a problem since anything on the tile itself will not penetrate the tile. To stain or permanently discolor or dirty the tile, a substance must penetrate the surface. That isn’t gonna happen with porcelain. It does depend on the specific texture, though. If it has small pits and crevices which stuff can get stuck in then you may want to rethink it.
Hello Roger, I’m almost ready to tile. Time to put down my beer and get started. A couple of questions though. Where the cement board meets the drywall do you sillicone the joint or thinset the joint? You use the notched trowel for applying the thinset to the tile, do you spread it on the cement board smooth or use the notch side also? Should I start with my border, I am coming off a corner for one edge.Thanks for your adviise.
Dave
Hey Dave,
You want to thinset the backer / drywall joint and use the mesh tape there as well. Always use the notched side on the wall, if you need more adjustment depth use the notch on the back of the tile as well, but the flat side on the back of the tile is usually fine.
I usually measure my border and mark it out on the wall then install the field tile. You can make adjustments to the border as needed – installing your border first leaves very exact measurements you need to meet without the ability for much adjustment.
LOL! Tried to learn as much as I could by reading endlessly on all the topics, but you still end up with a million questions when you don’t do this for a living.
Sorry I’ve been so inactive these days, I did not fall off the face of this earth, but the wall texture is finally done and I pick up primer and paint tomorrow in anticipation of starting the tile job. As soon as it’s sanded and then painted tomorrow, I will submit more pix. David did a wonderful job with the sheetrock/texture throughout the house. It’s been such a long haul.
Hello Roger. Because of the distance I need to come out from the wall in order to tile to the top of my tub, I need to use 1/2 drywall (or greenboard) and 1/4 hardi board on top of that. Do I need to line a plastic vapor barrier on top of the drywall, then screw the cement board right on top? How do you finish the plastic barrier around the shower head and valve? And lastly, I need build a ledge under the window (which will get very wet). Can I use wood, then plastic, then cement board and tile? Thanks.
Hey Matt,
You don’t want cement board over drywall – plastic or not. If you need your 1/4″ cement board bumped out 1/2″ either use 1/2″ strips of wood down along the face of your studs or use 1/4″ strips of wood along your studs and use 1/2″ backerboard.
Around the valves the plastic gets siliconed to the back of the backerboard around the back of the opening. This creates a dam that water will run around as it goes down your barrier.
Yes, you can use the wood / plastic / backer on the window, just fill your screw holes with silicone as you screw in the fasteners. Just squirt a dab of silicone and place your screw in the middle of it – it will seal the hole as you drive it in.
Roger
I wonder if Matt is thinking he needs to cover the tub flange with the hardibaker?
I dunno – let’s ask him:
HEY MATT! Are you thinking you need to cover the flange with the hardibacker?
He should be by shortly since we just bombarded him with replies.
I didn’t even think of that.
Roger,
I’m using backerboard and redgard. For the change of planes do I tape and thinset or just use silicone?
thanks!
-Dave
Hey Dave,
Just use silicone and paint the redgard right over it.
To save me from using a whole sheet of hardibacker I used three seperate pieces on the valve side wall. Now that there up…. the transition between the two is uneven…(BTW the seam between the two is vertical…if that means anything) anyway is there a way to tie the two together somehow or should I just take them down and install a new sheet? TIA
Hey Steve,
When you tape and mud the seam (with alkali-resistant mesh tape and thinset) it will tie them together to create a monolithic wall substrate.
I’m doing a standup shower using a vapor barrier and Hardiebacker board. Do I still have to use sealer on the Hardiebacker before tiling? Your instructions in the beginning don’t say.
Thanks for the info,
Steve
Hey Steve,
You should never use sealer on the hardi – that’s why it doesn’t say.
Unless by ‘sealer’ you mean a liquid waterproofing product such as redgard or hydroban. In which case you want one or the other – vapor barrier or liquid waterproofing membrane – not both. If you are just doing the vapor barrier that’s all you need – bond your tile directly to the hardi.
Roger,
I have a concern…I was reading back through some of you directions and tips and noticed something that I’ve overlooked. When I butted (minus the 1/8″) the backerboard up to my existing textured and latex painted drywall. I used silicone to seal the gap as recommended and rolled on the redgard over this transition about 3/4″ in which I taped off so that I could tile up right up to tape. Once tiling is complete, remove the tape and use latisil silicone to finish up. What I overlooked was that you recommended sanding the dry wall to accomplish a rough texture so that the redgard would adhere better. I applied the redgard on to the latex paint drywall. I hope this does not need to be re- done, but I will if it is certain to fail.
Any help is appreciated,
~Debra
Hey Debra,
You’ll be fine with just the 3/4″ overlap. That is mostly just a problem with whole walls that have been painted.
Roger,
Yeah! I love good news!
I was reading over a discussion between you and one of your followers. He was asking how to water proof around the control valve and you answered his question. I just couldn’t get the grasp. You said something about (something) being sandwiched between substrate and tile. I hate to ask you to repeat something that you’ve already explained, i just did’t get it. Also, will this technique apply for shower and tub plumbing. FYI- I cut a 4 1/2″ hole around the control valve as recommended by Moen for future access if needed and the holes around the plumbing for the shower and tub are only slightly larger than the pipe.
Thanks again,
Deb
As you are setting the tile place a bead of silicone around the opening. Then when you install the tile this bead is sandwiched between the tile and redgard creating a dam of sorts so when water runs down your wall behind the tile it will run around the bead of silicone and down into the drain rather than into the opening.
ok, that makes sense to me, thanks. I just read your post to Steve about using vapor barrier and redgard, not both. Is using both over kill or a bad idea?
It’s a bad idea. It creates two impervious barriers that will no allow any moisture to dissipate. This will lead to mold between the two barriers.
Roger,
So I ended up taking out all the walls of the stand up shower. I kept the ceiling intact.
Do I need to waterproof the hardibacker? There is a product _ i think its called mastek – that is painted on a dries like a plastic liner. Do I need this?
Finally, my biggst concern. Is there a best practice for measuring?
If the distance between my wall is X inches, what should by hardibacker be?
I am a bit scared, since these might be long cuts along the lenght of the board, don’t want to mess this up!
Thanks for your time.
Fazil
Hey Fazil,
Yes, you need to waterproof the hardi in some manner. There are several products which can be painted over the surface to waterproof it. Never heard of ‘mastek’ but I hope you aren’t referring to mastic, which is a pre-mixed tile adhesive which doesn’t belong anywhere near a shower. You can use redgard, hydroban, aquadefense, etc. They all work well.
You want all your boards about 1/8″ shorter than the distance in the area they are being placed.
In fact I was referring to mastic – this is what he home depot recommended. So do I paint the entire surface with the redgard etc?
Yup, the redgard will waterproof everything. Mastic doesn’t waterproof anything and isn’t even suitable to bond tile in the shower.
Hi Roger,
I’m getting to the point of installing the tub in my bathroom remodel and feel I’m at the point where I need to keep in mind a lot of different areas (plumbing, backer board, tiling, framing etc.). I’m a bit confused about the correct way to transition the cement board down to the tub. You mentioned and I’ve seen it on tv where the substrate rests just above the nailing flange of the tub. And not at all into the tub correct? I’ve also heard nailing the cement board a 1/4″ off the deck of the tub, which means the wall will bow a little. The manual for my acrylic tub suggests nail a 1/4″ furring strip to the studs and run the substrate 1/4″ off the deck. Thus the cement board runs into the tub and keeps it plumb with the wall. Makes sense to me, but haven’t seen or heard of that method anywhere else. Have you? Is there a reason other than bowing the wall not to have it run over the nailing flange? I guess my concern with leaving the substrate slightly above the lip is how do you transition the waterproofing membrane (kerdi) from the bottom of the backer board to the top of the tub? I was planning on using cement board and kerdi, but just read that you don’t recommend doing that so I’ll have to read into that a little more as well.
Thanks again,
Grant
Hi Grant,
Never once did I state that using kerdi with backerboard was something I don’t recommend – where did you read that? I have said that if you have backerboard with a vapor barrier behind it you don’t want to use kerdi over the front. I’ve also said that if you choose kerdi you do not need to use backerboard – you can use drywall. If I did write that I was likely drunk and misstated something – I need to fix it.
You can do it either way with the backer – above the flange or over it. If you go over it you will need to shim out the backer so it doesn’t bow. The kerdi is siliconed to the tub with either method. If you go above it silicone it to the flange, if you go over it silicone it at the very bottom to the horizontal tub rail.
Hey there,
I’m a DIY’er all the way. I have a fiberglass neo angle shower pan I plan to make a tile wall for. How do I transition from backer board to drywall?
Thanks,
Jason
Hi Jason,
Just like I’ve described in this post:
Drywall to backerboard transitions in showers
Thank you! One more question. Is it out of the question to just use sheet rock and kerdi to tile the walls of my shower? I really appreciate your help Roger!
Nope, it’s one of the recommended substrates for kerdi.
That 8 pointed star entry way is beautiful!
I have an outside corner where bath tub surround tile will meet textured dry wall. I’m not sure if I should use the paper-faced metel bead (no nail) type and if so, am not sure what type of adhesion to use on this paper-faced corner beneath the bullnose tile? Will use joint compound on soon to be textured dry wall.
Thanks again Roger,
Debra
Hey Debra,
Thanks, I really liked that entryway. I normally use a plastic corner bead there and float it out with thinset on the shower side and drywall mud on the drywall side. You can texture and paint over the thinset if your tile isn’t going all the way to the corner. The paper-faced will end up failing behind the tile – the paper gets wet and disintegrates.
I was reading a little more on your site and see where you prefer spectralock grout by laticrete . Do you also prefer latisil caulk?
I prefer latasil silicone. The caulk is good – the silicone is better.
Thanks a million, you’re the best!
THanks Roger,
THe last unknown for me, at least I hope, is what to do with the transition from textured dry wall to the backer board on my tub surround. As far as water proofing this seam. Can I redgard this 1/8″ gap and then apply thinset to float it out in order to make the two areas flush? Then overlap the tile , say 1/2″ or so. My gut feeling says this probably wont work as a good water proof?? I just know if I sand back the dry wall enough to apply Alk. free tape and then thin set this transition and then apply redgard, I will not be able to re-texture the dry wall and have it look like no work has been done there. I may have to live with that….the priority is water proofing.
Thanks as always,
Debra
You can fill the gap with silicone then redgard over where the tile will be. As long as everything inside the shower is redgarded it’ll be fine. Put a piece of masking tape where you’ll have the door and redgard right up to it. It doesn’t technically need to be taped and mudded, those two planes can move independently.
These articles make me more confident in installing my own vapor barrier, HardieBacker, and tile. But I do have a question for you needing clarification. When you say “Overlap the lip of the tub or base and silicone the back of the barrier to keep it in place.” – my installation is for a stand up shower stall, no bath tub. So does that mean my vapor barrier needs to overlap the lip (top) of the shower pan liner coming up the walls from the final slope? (i.e., the area near the “bottom” of the HardieBacker boards)?
Roger,
Thanks for the tip! Would I need to go out any farther than one foot or so from the tub with redgard? Should I be a little concerned about the silicone seal failing at some point, right?Question? This idea came to me last night after a bahama breeze. Would glueing a strip of hardie backer under the tub edge and keeping it flush then taping off the tub below tile line (preventing redgard tub) and then painting a little redgard down that strip and continueing out however far you deem acceptable be a good move? Then coming back with tile as you mentioned? I was just wondering if building, for a better lack of terms, a redgard dam from the tub bottom out on to the floor a little. You’re a pro and I certainly respect your opinion. If this is a bad idea…I’ll blame it on the bahama’s! I’m not a chocolate milk girl…
Hi Debra,
Nope, not a bad idea at all. That should work provided you get good coverage from the tub to the floor. You can paint it out onto the floor as far as you want – whatever makes you comfortable. You do not need to worry about the silicone, it will be covered up and the seal will not be subjected to abrasion of any sort – that is what breaks the bead.
Roger,
I am need of your expertise once again. I am now looking ahead to tiling my bathroom floor and notice there is a gap between the tub and floor. My tile is 3/8″ thick leaving roughly an 1/8″ gap. I should be able to float/ramp that difference with thin set, correct? I’ve read all your material about shower/tub waterproofing and it leaves me with my second question. How do you waterproof the tub and floor tile seam? What prevents splash out from penetrating the grout line at the bottom of the tub and in my case, sitting under the tub because its slighly lower than the floor? How can I ensure water will not leak through this transition thus causing spontaneous combustion of my little puppy??
Thanks again,
Debra
Debra
Hey Debra,
Yes, you can build that up with thinset. You need to waterproof your floor in front of your tub with redgard or something similar, then silicone the gap between the tub and floor – then tile. That will ensure water doesn’t go anywhere it shouldn’t.
Roger:
Should you always Redgard the floor at the tub before you lay tile even if there’s no gap?
Nope, that’s simply one way to waterproof the floor in front of it should you choose to do so.
I’m redoing a tile tub surround and am using redguard. I’ve already taped seems and covered with unmodified thinset and made sure all the niches were without gaps. What I don’t know how to do is seal the bottom of the hardibacker to the tub. At one point I was going to use Kerdi, but I decided against it so I thought I could still use Kerdi band on the bottom and glue it to the small lip on the cast iron tub and then reduard over that to get a complete water seal for the whole tub all the way around.
This doesn’t seem quite right, but I can’t get any other advice on how to do it.
Hey Brian,
You can do it that way but it’s much easier just to silicone that gap and paint the redgard right over it. While the redgard won’t adhere to the entire bead very well, the silicone is waterproof and painting over it will simply ensure all the open gaps or spaces are fully filled and waterproof.