Now that you have your curb built and your pre-slope done (if you haven’t done this yet check out How to create a shower floor, Part 1) you are ready to install your waterproof liner.
Purchasing a waterproof liner
When you order or buy your liner you need to get one large enough for your shower. The liner you get has to be at least one additional foot larger than each of your measurements. For instance, if your shower floor is three feet by five feet your liner needs to be four feet by six feet. This allows enough to run the liner up the wall behind your backerboard six inches each way. You also want to purchase two “outside” corners for your curb. These are pre-formed corner pieces to waterproof the ends of your curb after you cut the liner.
I usually order mine two feet larger in each direction. Six inches is the minimum. Specifications state that your liner must run up the wall at least three inches above your curb. So if your curb is three inches high your liner needs to run at least six inches up each wall. I usually go a foot above the curb – overbuilding your shower is rarely a bad thing.
Preparing your shower floor for a waterproof liner
It's supposed to be sandy!
Before you install your liner I need to say type this: your preslope will be sandy, it’s suppose to be sandy – it’s normal, don’t panic. If you have any high areas in your preslope you may want to scrape or sand it down so it runs in a flat, straight line from the wall to the drain. Notice I said typed “flat, straight” and not level – if it’s level water won’t drain.
You can scrape it down with a regular razor scraper or sandpaper – yes, sandpaper. If there is a significantly large dip in your pre-slope you can fill it with more deck mud. You’ll need to coat the pre-slope with thinset under the patch to ensure it will stay put. Don’t get all OCD about this, it doesn’t have to be perfect. Just make sure there are no major humps or dips and water will run from the wall to the drain without problems.
The next thing to do is take a chisel to your wall studs. You weren’t expecting that, were you? You want to notch out your studs about 1/8″ up to the height of the top of your liner. This is so you can place your backerboard over the front of your liner on the wall without them jutting out at the bottom. It allows your walls to remain flat all the way down to the shower floor. You will create “cavities” in your wall studs for the liner. 1/8″ is a bit larger than the thickness of your liner but it’s better to be larger than smaller.
When you place your liner in the shower you will be folding the corners so you want to allow enough room on one of the corner studs for three layers of the liner. I usually notch my corner studs out 1/4″. This allows enough to keep your corner square after the walls are up.
Placing the liner in your shower
Liner placed over pre-slope
Now it’s time to lay your liner in the shower and get it all lined up. DO NOT cut anything until you have the liner exactly where you want it. Make sure you have the top half of the drain flange removed before you place your liner over it. I’m not talking typing about the round part that unscrews, I mean the top half of the lower part which bolts onto the lower half. After removing the top half of the flange replace the bolts, this will serve as a guide when you cut the liner.
Center your liner in the shower with the ends running up the walls evenly. Also make certain you have enough of the liner draped over your curb so that you can attach it on the outside of the curb. I will usually place it so that the liner drapes up and over the curb all the way to the floor on the outside of the shower.
Cutting the hole for the drain out of your shower liner
Drain hole cut out of liner
After you have it properly positioned you can cut out the hole for your drain. Do this very carefully – there is no second chance. Take your utility knife and poke a hole through the liner directly in the center of the drain. From there cut in a circular motion toward the outside of the drain in a spiral. Only cut it out to the outside of the four bolts which attach the top half of the flange to the bottom.
Silicone under the liner around the drain
Remove the bolts from the flange. Now you need to place a bead of silicone under the liner around the perimeter of the lower flange. The easiest way to do this is to place the nozzle of the tube of silicone into the hole you just cut for the drain. Place a good size bead around the lower flange outside of the bolt holes, don’t get any in the bolt holes. This prevents any minute amount of moisture from getting under you waterproof liner. Press the liner into the bead of silicone all the way around the drain to ensure full contact.
Prepared liner ready for top slope
Now you can bolt the upper half of the flange to the lower. Do not overtighten the bolts. You want to squeeze the liner between the two but not so much as to crack the flange – they are only plastic, after all. That’s it, the drain is finished.
Now take your liner and place it up the walls into the notches you cut out of the studs. You can nail or tape the top of them to hold them in place. Only place one nail into the very top of the liner, never lower. In the corner you will fold the liner over on itself, never cut it. Place the folded part into the larger notches. There should be enough room in the notches so your backerboard will set flush onto the studs.
In my next post I will cover how to cut the liner for your curb and make sure it’s waterproofed properly.
Hi Roger. Thanks very much for all the good info.
Could you generally comment on your thoughts on the hot tar membrane method? It is very popular here in CA and our homeowners association requires a hot mop (whether I choose to comply or not). Also, what if anything does it change in your 3-part series about shower installs?
Thanks!
Hi Robert,
You are in one of the very few places that still do hotmop. Provided there is a pre-slope installed they work fine, there are simply much better, cleaner and more efficient systems out there. Nothing would change except the type of liner.
Thanks Roger. Have a Happy Friday and a good weekend.
what tile do u recommend for shower floor?
Hi Mike,
Whatever the wife want.
Porcelain is normally the best choice.
Hi Roger,
I used fortified thinset for my preslope. It has cured for about 5 days and developed cracks. On checking it this morning, I find that about half the bed sounds hollow. it hasn’t bonded to the concrete floor. is this going to eventually crumble and break down or am I safe to put the membrane over it and procede? Thank you.
Hi carla,
You need to remove that floor. Mud decks are made with deck mud, not thinset. The thinset will not last.
Love the comedy and clarity you give
Quick question: When installing a shower in the basement on a cement floor, is there a process for the curb (yes, used cement bricks. corrected after initially installing 2x4s) to lathe and mud before laying the liquid waterproofing on the deck mud? Also, what state should the deck mud be to roll the hydro ban on it?
Thanks much in advance!
Hi Jody,
Process is the same whether you are going over 2×4’s or bricks. Just fold the lath over the bricks and use wet mud to form your curb. Your wet mud, and deck mud, must be cured for three days before using hydroban to waterproof them. If you want a skinny curb you can simply skim-coat the bricks with thinset, let it cure, then hydroban it. You don’t necessarily need the lath and mud.
Hi Roger,
Could you tell me a little more about how to cut, secure, and finish the membrane when you are using concrete bricks for the curb?
Thanks,
Charles
Hi Charles,
It’s exactly like a wooden curb. Cut your liner over it at the ends, install dam corners, install bent wire lath over it to hold it in place and cover it with wet mud to form the tile substrate for your curb.
Regarding cutting out a relatively large hole in the liner which is larger than the bolt circle of the flange nuts so the silicon can be put under it…my drain has a groove that inches the liner between the floor mounted section and the top half. Seems like putting silicon into this groove would do the sealing job and be more consistent. I suppose putting the silicon here would protect against the bolts loosening over the life of the shower?
Hi Ron,
Yes, you can fill that groove with silicone to seal your drain. The bolts aren’t going anywhere.
Im sorry if I have missed it, but when installing a liner on a rectangular shower in the corner of a bathroom with dual curbs, how do you prepare the outside corner of the liner where the curbs come together? All the illustrations I have seen are showers between walls, my shower glass and curbs will come to an outside right angle, and I want to get the liner tucked in right. Thanks
Hi Reilly,
The best way to do it is to cut the liner at the corner and weld (with the oatey adhesive) an outside corner to the inside (upside down) and an inside corner to the outside of the curb (upside down).
Cut the liner on a total diagonal? Splitting the corner on a 45*? The situate the corners like your saying, my curbs are three 2×4’s stacked. Will those. Order pieces overlap in the center covering the whole cut? Or should I leave and overlap of the liner and glue the seam then put the pre made corners? Sorry for so many questions, I refrained from as many as possible… Thanks Reilly
also I went by the siouxchief installation info, and the said to cut a 4.5″ hole, which I have. Now with the drain sitting flush before lathe, there is only a 1/4″ of preslope. I’m tempted to re-drill the hole in some 3/4″ flooring 4″ so the drain rests on the flange bolt holes and raises the drain up for your recommended >3/4″ preslope, what is your opinion?
The 1/4″ at the drain is fine for a pre-slope beneath the liner.
Yes, split the corner on a 45 then overlap and glue them. Then install the corner pieces as I described over the corners, they should cover the cut.
Been about 22hrs. Droplet still hasn’t fallen under its own weight.
I’m doing the flood test. One of the bolt cavities that hold the ring on has a very tiny pinhole on the extreme bottom where it is flat. Manufacture defect. In the last 4 hours the water droplet hasn’t gotten big enough to drop under its own weight. Is it safe to replace the bolt for a shorter one and fill the cavity with silicone , or start over with a new one?
Go ahead and silicone it if you want.
Hi Roger. Just a question. I’m a farm boy, and as most farm boys are, we overbuild. Whether it be with iron or wood. With so much emphasis on pre-slope, waterproof liner,weep holes,pea gravel,final slope,vapor barrier, why are the weep holes so tiny in the drains? If the water is supposed to get out, I say let it out. Why tease it. I so wanted to take my dremel and make the slots bigger. I thought of this as I put a tad to much silicone under the liner and squeezed some out into the clamp ring and plug one slot. Maybe I’m thinking all wrong, if they make a slot make it worthwhile. Thanks for your past help and information!
Because it’s only a very small amount of water that will be draining into it.
Hey, just checking, if I do 1/4″ per foot slope on the sub deck, I should also do 1/4″ slope on the second, the tile deck, which in total gives me 1/2″ per foot slope from wall to drain?
Hi Michael,
It would be a consistent thickness on your top mud deck, but it will end up being 1/4″ / foot because it follows the preslope.
Originally, I was thinking about installing a traditional floor with a traditional wall (vapor barrier behind the backer board). I have already installed the pre-slope with a conventional drain. After reading your website and purchasing the Kerdi shower proofing for walls, I have decided to go with kerdi sheets for the walls as I think it is a better solution. My question is how do I join the kerdi wall to the traditional floor without ending up with the infamous mold sandwich? I was thinking about putting a folded two inch band of kedi which would seal the wall to the 2nd layer of mud above the plastic liner. Thanks.
Hey Jim,
You nailed it. You can either use kerdi-band or just run your sheets from the wall 2″ onto the top mud deck.
Hi Roger,
Thanks for the reply… I did install a membrane on top of the first mud bed, which is 1 1/2″ thick at the drain, going to 3″ thickness to the walls.
Then I applied the second mud mix, but did the thickness less than 3/4″ at the drain and the rest of the base. The second mix, which went on top of the membrane, is about 1/4″ at the drain, then not more than 1/2″ over the rest.
To be clear, when doing the pan, I first installed roofing paper, then mesh, then 1 1/2″ decking mud, at drain, graduating to 3″ at walls. When this dried, I installed the membrane, then a 2nd mud deck mix, with the mix being 1/4″ at drain, graduating to 1/2″ at walls.
The drain, in total, has mud mix thickness to 1 3/4 inch, then at the walls, to 3 1/2″. MY WORRY is whether or not the second layer would be strong and durable enough. What do you think?
If second layer isn’t strong enough, should I remove it, and the rubber membrane, then coat the thick, 1st pour with a topical waterproofer, then tile on top of that?
Thanks again..
It won’t be strong enough to serve as a top mud deck with tile bonded to it. Absolute minimum is 3/4″. You can take out the top bed and install another with a 3/4″ thickness, or you can use a topical membrane after removing the membrane, but you’ll need to figure out how to tie it into the drain, it doesn’t work the same way with topical membranes. You can only use a topical membrane on your floor if you have the same on your walls.
Quick Question…I read, then tried to remember, wrongly as it turns out, the creation of the mud pan. How can I correct the error of my ways?
What I did…I took the proposed total measurements for the finished deck mud, 1 1/4″ from drain to 3″ to shower wall. In the first application, I essentially poured, what should have been done in two steps. So, to be clear, the finished depth in 1 pour with no waterproof membrane. I did, before the pour, install the felt paper, then the mesh, then the concrete with your deck mud recipe.
When I realised I should have halved the amount, I was gutted. Since, I put the waterproof membrane on top of the thick decking, but to avoid a huge dam, I then put a 2nd concrete coat on top of the installed membrane. I would estimate the 2nd thickness to be 1/4″ at drain, to not more than 1/2″ at points furthest from the drain.
Now, I’m simply nervous about the 2nd layer being strong enough. I have been thinking about applying a bonding agent, then another layer of mud on top, say another 1/4″ at drain, then another 1/2″ to point furthest…after which a 1/4″ thin-set bed for mosaics going down on the shower floor.
Or, can I leave all as is, and then just install the tile, with 1/4″ thin-set?
OR, can I put down, with a bonding agent, an independent layer of thin set, let it go off, then again, more thin set plus tile? HELP!
Hi Bonce,
You need to either put your membrane on it and another mud deck with a MINIMUM of 3/4″ at the drain, or remove it and begin again. You can also switch to a topical waterproof membrane which would go directly over the top of what you currently have then tile directly to it. You would need to use it on the walls as well.
DO NOT put tile directly to what you currently have with no waterproofing! Seriously. Thinset is not waterproof (but you already know that).
Roger,
Thank you for the outstanding web site. Can you comment on why you prefer to cut out a relatively large hole in the liner which is larger than the bolt circle of the flange nuts? Other sites I see only recommend cutting a small X in the liner around each pre-installed bolt. After the flange is installed and bolted down, a hole is cut out for the drain itself.
The method of cutting small X’s seems like there would be less chance for water to go where it shouldn’t. But I guess the liner will tend to “bunch up” a little bit when the screws of the flange are tightened down.
I’m sure that there must be some method to your madness which I would like to understand.
Hi Jim,
It is required to place a bead of silicone around the outside perimeter of the flange bolts between the liner and bottom flange. You can’t do that if you only have x’s cut out for the bolts. It could also hinder the drainage of the weep holes depending on where they are placed in your particular drain.
What do you do when you have a shower pan that is not at all square. One of those artsy-fartsy things, you know. Do you use a topical, or piece together the pvc one with glue or a combination or what? Thanks, Roger.
Hey Ken,
You can do either but a liquid topical membrane like hydroban or redgard is MUCH easier and quicker than trying to do it with a pvc membrane or even kerdi.
What goes on top of your liner
Deck mud.
In your drawings you show the bottom flange of your drain about 3/4 in above your subfloor, what should I do if my drain flange is sitting just about flush with my subfloor.
Thanks in advance
He Vinny,
Raise it.
Normally the drain flange rests on the subfloor so you’ll only have about 3/8″ of mud up to it – that’s fine.
Ro
ger,
I bought your eBook “Creating a traditionally waterproof shower” and it gave me all the knowledge I need to build my shower however it didn’t give me any of the skill to actually do it right. When I finished my pre-slope yesterday I thought everything was sloped flat to drain but today when I put a level to it I found a significant dip. You said typed:
“If there is a significantly large dip in your pre-slope you can fill it with more deck mud. You’ll need to coat the pre-slope with thinset under the patch to ensure it will stay put.”
I would have thought to let the thinset dry before putting the mud on but I saw another comment about putting the mud on when the thinset is still wet. Does this mean that I make both the thinset and mud at the same time and lay the mud right after the thinset or should I wait to let it cure a little while? Can I use the thinset alone to fill the dip?
Please help me out with a little more explanation. My wife is looking cross and my dog is starting to smolder.
Thanks,
Sam
Hey Sam,
Always set anything into wet thinset – not cured. Yes, mix both and install the mud right after the thinset. If your dips are less than 3/16″ then you can just float it out with thinset.
My liner came folded up, so it has some creases in it… it will probably flatten out once the mud is on it, but is there a way to flatten it out? I tried a hair dryer, didn’t seem to do much. Thx!
Yup – pack mud into it.
The creases aren’t going to hurt anything. Just make sure it isn’t folded over anywhere.
Thx! I have blocking to the top of the shower pan (built a 4″ curb all the way around), is there any reason I need to put in more?
Nope, that’ll support it just fine.
Roger,
My basement has a 4′ tall cement foundation wall that is one side of the shower I’m building. After installing the pre-slope deck mud how would you attach the membrane to the concrete? I planned on tiling directly on the foundation wall inside the shower and throughout the rest of the bathroom, would you recommend this? Any help would be great. Thanks
Hi Ben,
Unless you are installing a substrate of some sort on the wall, such as a bumped out wall or cement board with tapcons, you’ll need to use a topical membrane for the floor. The tile will not stick to the membrane, whether it’s bonded to the wall or not. If you don’t cover it with a substrate you cannot cut it off any lower than three inches above your curb.
Roger,
Thanks so much! You can add marriage counselor to your list of expertise. I was going about this shower the wrong way from the beginning. I have torn down everything I did and started over. I just have two more questions for you about the existing cement in my soon to be new bathroom. Would you recommend putting plastic behind the cement backer board overtop of the foundation wall in the shower, Also would I use backer board across the floor which is the cement pad to my home?
Hi Roger,
I applied thinset over my deck mud and planned on floating some low spots with more mud. Problem is that I let the thinset cure. Can I reapply thinset and then apply mud when it’s wet?
Thank you, Chad
Yes.
Roger, here’s another silly question, when you fold the liner at the corners, can you use PVC liner glue to hold the folds together instead of notching the studs 1/4″? Would that work?
Yes, the glue will hold the folds in place. The notches, however, are not to hold the liner in place – they are to create space for the extra liner material which is folded over. The folds have three layers of liner in a small area whereas the rest of the wall will only have one layer. Without either notching the studs or shimming out the rest of the wall your wall substrate will bow out at the bottom where it goes over the liner. It will not be flat at the bottom – notching the studs prevents that.
Thanks for the clarification, the installer had never heard of this—he said that he always nailed the liner to the studs on the corners. When I told him that was a complete NO-NO unless it’s above 6″, he answered, “…how else do you hold it in place?” I’ll tell him this when he shows up on Monday. Is there any other way to hold the bulge at the bottom other than the notching? Yikes, I’m getting real nervous……
You can shim out the studs above the liner to the thickness of the liner with drywall shims.
I’m cruising the videos in preparation and trepidation of building a curbless shower. One video had the corner two bys a little apart so you could tuck the folds in between. Interesting.
Here it is I had to find it again.
http://www.youtube.com/watch?NR=1&feature=endscreen&v=JNB8bs5VYoI
Yup, I do that whenever I run across the corner studs like that. It’s really handy. Rarely happens, though, unless I’m replacing studs.
hey jackass, I really need the next post! (and the next and the next!!!) that liner is thick and a pain in the butt… especially for a neo angle curb… any advice on how to fold it and make it stay without killing something in the process??
Hey Geodans,
You’re in luck – it’s been right here: Create a shower floor – part 3 for about a year and a half.
right here? where?…. did I miss something?
Crap, sorry. I fixed it. Musta had a beer or two when I answered you.
I have a vinyl shower pan that is collecting water and over flowing to the floor below. I think the weep holes in the drain must be blocked. Is there any way to fix this other then ripping it all out?
Hey Jack,
Unfortunately no, the only viable way to ensure it is correct is to remove it and replace it with a properly waterproofed base.
Hi Roger,
I purchased your manual on liquid waterproofing shower floors and walls. It is very helpful! One thing I’m not clear on is the gap between the mud pan floor and the cb walls. I will leave a gap there of 1/8. But how do I seal that gap? I know the traditional liner would go up the wall. Will the hydro ban seal the gap? Or do I need fabric or silicone in the gap then hydroban?
Thanks!
Hi MJ,
It sounds like you are trying to do a liquid topical pan with traditional walls – is that the case? If so you can not do that. The barrier behind the walls sits behind the waterproofing on the floor – no way to get that water into the pan. You can do topical walls with a traditional pan, but not the other way around.
If you are doing all topical you would install your walls first down to within 1/8″ or so of the floor substrate, then install your deck mud right up against the backerboard. The membrane is just painted across the floor and onto the wall without a gap. If you want to leave, or have, a gap there you can fill it with silicone and paint right over that or use a solid fabric like kerdi or nobleseal – not mesh – and paint over it.
If you are trying to mix the methods and that is the way you were going to do it let me know how you would like to build it – topical everything, traditional everything, or traditional floor topical walls, and I’ll get the correct manual to you.