I get a LOT of questions from my readers about basic shower construction. I understand that my readers don’t consider this stuff basic and there’s no problem with that. The problem is that I end up answering the same questions over and over and over… So, to save what very little is left of my sanity (which is a number roughly equivalent to absolute zero) I will cover some basic things here so I can simply reply ‘read this’.
If you’ve been channeled to this page by one of my smart-ass comments please take no offense to it, I’m here to help. Please understand that I currently have over 12,000 comments (questions) on this site (seriously) which I’ve answered – every one of them. I’m just trying to make your life (mine) easier. I will continue to answer every question I’m asked, I’m just super cool like that. 
If, after reading through this, you still have questions feel free to ask them in the comments below.
You can also download my shower waterproofing manual which should answer a lot of questions and cover basic techniques and methods you may be confused about. Go ahead, it’s free. So without further ado (doesn’t even look like a word, does it?) let’s get on with it. (For all my readers who feel the need to correct me: I KNOW it’s actually ‘adieu’ – I was being facetious. Thanks. 
)
Leaks
First and foremost – tile is not waterproof. Grout is not waterproof. Adding sealer to your tile or stone will not make it waterproof. Your shower should be completely waterproof before a box of tile is even opened! No matter which waterproofing method you choose, proper substrate preparation is the only thing that will make your shower waterproof.
If you have a leak in your shower – stop using it immediately if at all possible. If that is not possible (it’s your only shower) have the shower repaired – immediately. If you see water leaking it is likely not nearly as much water as you don’t see leaking into your wall cavity and structural framing. By the time you ‘see’ most leaks the framing is normally already considerably compromised.
No, there is nothing you can put over your tile to make your shower waterproof if you have a leak – not even sealer. A tile or stone sealer is made to make your tile and grout stain-resistant, not waterproof. It does this by sealing the pores of the tile and stone to slow (NOT STOP) the absorption of liquid and prevent staining. It only means you have more time to clean up the spilled red wine cherry kool-aid before it stains anything.
Substrates
Drywall is not an acceptable substrate for your shower unless you are using Schluter Kerdi waterproofing membrane – that’s it. Cement backerboards are the standard and there are also other products such as waterproofed, gypsum based boards like Denshield and waterproofed, foam-based sheets like wedi or kerdi board.
Cement backerboards are not waterproof. They are water stable, which simply means that they will not swell or disintegrate when exposed to moisture or water – they won’t change size. But they are just like your driveway, they will soak in water, hold water, and dry out, just like your driveway when it rains. If using backerboards there needs to be a waterproof membrane utilized as well.
Membranes
If you are using a topical waterproofing membrane such as a liquid like redgard or hydroban, or a sheet like kerdi, do not use a moisture or vapor barrier behind your substrate. If you have a vapor or moisture barrier behind your substrate do not use a topical membrane on the front of it. This combination creates two waterproof barriers with your substrate sandwiched between them. any vapor or moisture trapped between them has absolutely no way to dissipate. This is lovingly referred to as a ‘mold sandwich’. It is not tasty. Use either a moisture or vapor barrier behind your substrate or a topical membrane on the face of it. One or the other – never both.
With that said, if you want to use a topical liquid such as redgard on the seams of your backerboard, after you tape and mud them, you can do so without problems. If your moisture barrier and backerboards are properly installed there is no real reason to do so – but if it will help you sleep at night go ahead and do it.
If you are using a topical membrane and you have an exterior wall with either plastic facing or kraft paper facing you need to cut slits into that facing before installing your substrate. If you do not it will create the aforementioned mold sandwich. Give moisture or vapor somewhere to dissipate.
Shower-tub transitions
There should be a gap between your tub or acrylic shower base and the bottom of your backerboard. If you are using a traditional barrier waterproofing method you do not need to do anything with this gap. Do not fill it with silicone! This will trap moisture running down your barrier and it will have nowhere to go. If you are using a topical method you can fill it with silicone if you want. If you are using liquid you should fill it with silicone. This creates a waterproof plane between your membrane and the tub or base so water or moisture ends up in the drain rather than in your wall.
When you tile you can tile right over that gap. You should not fill this gap with thinset behind the tile – it will crack due to movement. Your wall and tub or base will expand and contract at different rates – it will crack any cement-based product you place between the two. This includes thinset as well as grout. You do not need a solid backing behind your tile over this gap – it should be less than 1″ wide. You shouldn’t normally be walking on that tile in that particular spot. Yes, it can just hang there.
Grout
If your grout is cracking it is due to movement 99.9% of the time. Type ‘cracking’ into the search box up there and you’ll find in-depth explanations for your viewing pleasure.
If you have white, or lighter than normal grout when you’re finished grouting it may be efflorescence. This is mainly due to minerals in the water being left on the surface of the grout when the water evaporates. It is usually indicative of either incorrectly mixed grout or using too much water while cleaning the grout – not wringing out your sponge enough. This is normally only on the surface of your grout. Scratch the very top layer of your grout in an inconspicuous spot with your fingernail. If you have the correct, or at least a darker, color beneath the surface that is the likely cause. The easiest, quickest fix, provided it is only the very top layer, is to get some drywall sanding sponges and go over the grout lines very lightly. Just like burnt toast – scrape it to the color you like.
Corners and changes-of-plane
Caulk.
Disagree with me?
Like any other website I get my fair share of people who disagree with my methods or techniques – it really doesn’t bother me. I am more than willing to have a civilized, intelligent conversation about anything tile related. If, however, you simply attack me personally and act like an uncivilized ass I will call you on it – and not in a nice way. I write this blog in a particular manner, it does not mean that I take my profession lightly – I most certainly do not. If I wanted to be a pompous bastard I currently have 19 letters I can place after my name – all tile related. But I’m not a pompous bastard – you can just call me Roger.
If you are a contractor with a customer who has come here for information and I’ve told them you’re wrong – realize that the extent of my knowledge of that particular project is limited to what I’m told by your customer. It does not mean that I am ‘out to get you’ or anything of the sort. I normally limit my replies to those situations by stating the current TCNA and/or ANSI standards pertaining to what I’m told. If you disagree – please let me know in a civil manner, If you’re correct I’ll back it up – I do this everyday, too! If you’re an asshole about it expect the same in return (It’s the comment by ‘Kanela’ with the bold print before it) – and please have a thesaurus handy to interpret my reply – I’m a very well educated asshole.
That’s it for now. I will likely add to this post on a regular basis. If there is anything I’ve caused confusion with please, for the love of God, let me know. I can change this page since, you know, it’s my website and all. If you have any questions at all please ask them below – I’ll answer, really.
Can you use polyethylene as a vapor barrier (instead of tar paper i.e. roofing paper) between a mud deck and plywood subfloor when building the shower base?
Hi Conrad,
Yes you can.
Hi Roger,
I recently purchased a new home with a tile shower with a bench/seat in it. The grout at the 90 degree angle from seat to floor is cracked. Sometimes water leaks to the basement below the shower after using it. I’m not sure how the shower was constructed before I bought this house. How can I fix this leak? Should I use grout, silicone caulking, or something else? I sent you an email with pictures titled “shower tile bench question” I believe. Thank you
Hi Todd,
The bench is likely the source of your leak. There is nothing you can do over the tile to prevent it, you’ll need to do some exploratory surgery in your shower to determine the root cause, then takes steps to fix that. It may or may not be the crack you mentioned, any change of plane should be siliconed, not grouted, because it cracks just as you’ve described. It should not, however, compromise the waterproofing if it was done correctly.
After a couple battles with a leaking shower, we relented and tore the whole thing out. The problem seems to have been a 3″x 1″ notch cut nearly to the floor of our shower pan liner…presumably to make the transition from a half wall to the entry easier?!?! At any rate, we plan to reinstall a new tiled shower and currently have the shower gutted to the studs and cement underlay. We are ready to put in the shower pan liner, but have a concern about the original cement underlay. It is a 4’x5′ base…the cement pad doesn’t start it’s slope until about a foot in and then it slopes quite quickly. Also, in each corner of the cement underlay, there is a golfball size indent…basically like you’d see in a pool que chalk…no idea why it’s there in each corner. Our question is…can we compensate for these low spots in the cement underlay and the improper slope when we make the shower pan, or do we have to chisel out the whole cement underlay…which would be a HUGE undertaking! …or is it possible to fill these indents with cement before we install the liner. Would these corner indents cause the pan to drain improperly and cause us long term problems? THANK YOU SO MUCH FOR YOUR ADVISE!
Hi Ipo,
You can fill in those indentations and fix your slope by putting thinset and more deck mud over the areas that need to be fixed. They may cause problems, you don’t want anywhere in your liner for water to pool.
Hi Roger,
I have a floor to wall shower and having problems keeping silicone at the floor/wall joint. I have redone 3 times in in about as many years. Am I using wrong products? Was told to use sand caulk by one and non sand caulk by another sales rep. Any help on this would be great thanks.
Bill
Hi Bill,
Use silicone. The two products you are using are acrylic caulks, not silicone.
Hi Roger,
I uploaded some pictures and need your advise the pictures are uploaded under the subject GAP.
I messed up
and asking for what to cover the 1/2″ gap – please take and look at the pictures and let me know what the best option is.
Grout – caulking – strip of 3/8″ porcelain? Or maybe some other alternatives?
Thanks and very much appreciated
Tony Mazz
Hi Tony,
With an outside corner like that you can actually grout it. It will normally be fine. If you don’t want to do that get a backer rod (it’s just cylindrical foam) and stuff it in there, then silicone over it. But grout should work just fine.
I have a question regarding the use of the felted waterproof barrier system for a bathroom floor. One video said to us latex along with the thunder to apply to the subfloor and then lay the barrier on top of it. What kind of latex and how much should’ve mixed with thunder?
Thanks
Susan Bushinski
Hi Susan,
Not sure where you got that information but a couple things:
1. I have no idea what a ‘felted waterproof barrier system’ may be. Never heard of such a thing unless you’re speaking of a mud bed – in which case you really need to reevaluate your installation method – that’s a highly specialized installation.
You don’t need to mix latex with thinset any more, we’ve had modified thinset with the latex polymers in the powder for about thirty years now.
2. I assume your phone changed the work ‘thinset’ to the word ‘thunder’.
What you’re speaking of is a typical installation method from the mid-60’s. It’s no longer needed and there a LOT of more modern methods available which are much easier.
My shower is done and really beautiful. I used Kerdi throughout and impervious 12 x 12 porcelain wall tiles and 2 x 2 porcelain floor tiles. I grouted with Spectraloc Pro Premium. My wall to floor perimeter is caulked with silicone.
In one of your recent posts the homeowner was concerned about water trapped behind the wall. This raised concerns for me. With spectralock grout everywhere and waterproof silicone at the floor/wall junction, am I not going to have water behind my tile also that can’t drain through the silicone?
Also, water that makes its way to the pan: How does that drain through the mortar and the Kerdi plastic drain parts that are inserted at the time you tile the shower floor? It seems to me that the plastic insert for the Kerdi metal drain would block water from flowing into the drain pipe.
Please help me understand how all of this works. I know I have a waterproof shower and an effective drain because the pan passed the flood test before tiling. However, now that I have tiled the floor I can’t see how water UNDER the tile can get down the drain easily.
Thank you so much for your help throughout this project.
Hi Jeff,
Gravity.
The water will run behind the tile through the mortar over the surface of the kerdi. Your silicone line should not touch the kerdi in the corners, that would be a hell of a lot of silicone if it did. Like 1/2″ deep. The plastic insert into which the drain top snaps is held in with mortar. The bottom of that tube does not fully contact the bowl in the drain, allowing water to seep beneath it into the drain.
I have a shower that was tiled directly on the drywall. Should I be concerned about this? With everything I have been reading here and elsewhere, it sounds as if I should be. I am ready to rip down all the tile and have it redone. What do you recommend?
Hi Anna,
I recommend having it redone. It may be fine, it likely won’t. Tile and grout are not waterproof, water will always get to your substrate. You need to have a waterproof substrate of some type behind your tile.
My shower floor is a preformed stone composite that has developed almost invisible hairline cracks,causing seepage. The shower walls and the rest of the bathroom are tiled with 8-1/2″ terra cotta color tiles that don’t seem to be a standard sizes since I have not been able to find them. My handyman tells me that he would have to replace the bottom three or four feet of tile if he replaces the shower floor, which would result in an unsightly mismatch.I was hoping I could just waterproof the shower floor. If not, what are my least costly options?
Hi Edward,
There is no product I know of that you can waterproof that shower floor with. Your contractor is correct, you’ll need to remove at least the bottom 2′ of the shower walls to incorporate a new shower floor. That is your least costly option. Maybe find a tile that goes with what you have and do the two feet at the top and bottom of the wall? So it looks like it was done on purpose. Or just replace all the tile.
Hi Roger,
Over the weekend I re-grouted our stall shower (there were large sections of grout missing). Prior to fixing this shower we had to use it a few times because of problems with our other shower. That was over a week ago. After applying the grout to the stall shower everything seems to be drying ok except for some of the bottom seams, where the bottom tiles meet the wall tiles. There are some 1″-2″ sections where the grout is darker and if you put your finger against them, your finger will look a tiny bit moist, so there is definitely moisture present. We put a fan in the shower to try and help the grout dry and it has worked in some sections but not all. Could water have gotten behind the tiles before re-grouting it and it just needs more time to dry out? Also we live in an apartment with people above us, but we don’t see any water damage on the outside walls or any other areas in the shower, like the walls or ceiling tile.
Thanks so much for any insight you can provide.
Hi Allison,
It sounds to me like the water is not draining into the floor membrane from the wall and getting trapped at the bottom of the wall. The space between the wall tile and floor tile should be siliconed, but only to the depth of the tile to allow water to run behind it into the floor membrane. If you’ve grouted it the grout is trapping the water at the base of the wall. It will still drain, but it’ll take forever.
I need to build a fireplace hearth with a tile or granite top and sides (wood burning fireplace).
What do you recommend regarding the relative finished height between the top of the hearth tile (or granite) and the top of the fire brick?
I was thinking of putting the tile slightly (1/2″ or so) above the fire brick, but am wondering if there is a heat damage issue. i.e. will the heat crack or damage the tile or granite on the hearth?
The reason I want the hearth slightly higher is to maybe help contain spillage of coals or ashes from the firebox onto the hearth.
What’s the norm? What do you normally do?
Hi John,
I normally have it even, but you can raise it some if you want. The heat isn’t going to affect anything at all.
So my contractor did a lot of crap things on our house but our current (only working) shower/tub takes the cake. We’ve spent hundreds on a plumbing fixing all his issues that he did incorrectly. Anyway, all the plumbing is fixed but there’s still a very slow leak coming for the outside of the tub and only when we take a shower. We caulked around the plane changes (which he didn’t do) it slowed it down but didn’t stop it. I know he used hardy backer, but what else could be it? We also filled all the grouts spots that he didn’t do.
You don’t happen to live in the San Antonio area, ha?
Hi Janelle,
Although he may have used hardibacker there is likely no waterproofing in your shower. Cement board is not waterproof, it still requires a waterproofing membrane of some sort.
I need a pro tip…if one exists. I purchased your design guide and it helped a great deal to get me started. I’m installing my shower tile on point. In fact it’s a 6 tile pattern on point. The first wall is finished and it looks great! Now I need to continue on the next wall and I need to make the turn on that inside corner. Unfortunately my angle is not a perfect 45 degrees. The tip I’m looking for is how to figure out what angle to cut the tiles on the next wall so that grout line wraps perfectly to the next wall. I made one attempt already and got about 4 tiles up and could tell I was beginning to miss my grout line more and more with each tile. I pulled them off and decided to start again.
Any tips to help me keep those wrapping grout lines straight?
Thanks a ton,
Mike
Hi Mike,
You can draw a level line whatever distance the corner of the bottom tile is from the wall you’re wrapping all the way up the wall. For instance, if, when you wrap the first tile, the corner of it is 6″ from the wall, draw that line level all the way up from that point. (It should be 6″ all the way up if your wall is level). When you cut each successive tile measure from that line to the CORNERS of the grout line of the tile you’re matching. For each tile you’ll have two measurements, one to the bottom corner grout line and one to the top. The cut WILL NOT be a 45, but once that row is up your pattern should be.
Did I just confuse the hell out of you?
Thank you SO much for trying to explain! Even though I don’t get it (yet), I’m so relieved to know there is a method!
Yep, to your final point, I’m confused. I’m reading the tip over and over trying to picture it, but it’s not coming to me. I also made a mistake in my explanation, but I don’t think it matters. My tile pattern is a 4-tile pattern on point, not 6-tile. I’ll explain the layout at the bottom if it matters.
My confusion:
1. In your example when I draw the 6″ line ‘up’ the wall, I think I figured out you meant plumb (vertical) not level (horizontal) correct?
2. Do I draw that 6″ plumb line on the new wall or the old wall? I think it’s the new wall.
3. The big one…I don’t think I understand how I measure for the tiles on the new wall. If my first tile on the original wall is 75% whole and only a small corner of that tile should wrap onto the new wall, how do I measure for that little piece that belongs on the new wall? What I pictured from your example would put my plumb line way out beyond where the new piece would start.
Is it possible to sketch something on a napkin and email me a snapshot of that?
The pattern: I start with an 8×8″ tile on point. Then I put two 4×8″ tiles on each of the bottom diagonal edges. Finally, I put a 4×4″ tile on point directly below the 8″ tile and between the two 4×8″. That makes the 4-tile pattern a 12×12″ pattern in total.
Thanks a ton! I feel a huge weight lifted knowing it’s possible.
Mike
My wife and I discussed your explanation and I think we figured out you are talking about a slightly different pattern than we are talking about. I think you are talking about creating a mirror image on the next wall. For example, if I have a large tile on the first wall with just 2″ of the right point cut off, the matching tile on the next wall will be the exact same size with 2″ cut off its left edge. Is that what your technique accomplishes?
If that is the case, and you follow a grout line down my original wall to the point it connects with the next wall, the grout line stops the downward angle and now goes back up the next wall. The grout lines connect, but it is not the look I’m trying to accomplish. What I’m trying to do is continue that downward angle of the grout line onto the next wall.
Is there a way I can attach a picture? I could explain it better if I can.
Thanks,
Mike
No, I hate mirrored patterns.
You can upload a photo here.
1. Yes, I meant plumb.
2. Yes, the new wall.
3. It doesn’t need to be 6″, I only used that as an example. If your tile on the original wall is 75% and your tile, point to point, is 12″ (example), rather than measuring 6″ onto the new wall you would measure 4″ for the line. 12″ – 75%. That 4″ line would give you the guide to place the corner of the 25% portion of that tile. You should only need one line, everything else will line up with the grout lines, I’m assuming. If needed you can draw several of those plumb lines depending on what size the remainder of your tile is for each size.
Hi,
I recently purchased a “new” townhouse (no one has lived there before me),
I’ve noticed that when I take a shower my grout looks as if it is running & it becomes like a gummy substance that it looks as if the tub has not been cleaned in years… Did the installers use the wrong grout?
Hi Lisa,
Not too sure if what they used was actually grout. That doesn’t sound like anything grout-related (no grout would do that). It’s apparently incorrect, but I have no idea what it may be.
Hi, do I need to waterproof the cement backerboard before tiling? And what do I néed vapor barrier behind backerboard?
Hi Craig,
You need either a waterproof membrane over the face of the cement board or a vapor barrier behind it. One or the other, never both.
Had a whole bathroom tear out , the tile hasn’t gone so great.Had beige grout on floor and walls turned out white Had a dark grout on showerfloor unsanded with 2 x 2 tiles. Turned white, contractor came regrouted grout I sealed with 511 miracle 2 weeks after grout done and then 3 more times with 3 to 4 days in between each application until grout didn’t turn dark when wet. Showered for the first time a week later. Well now I have an area that turned very dark around drain with a trail to one wall. We haven’t showered for 2 weeks in that shower and have had a fan in shower trying to dry it. The grout is VERY slowly lightening up. Thought I would try to reseal when dry or can I have too much sealer. My contractor will not return my calls. Do you know possibly what’s going on and what I can do to fix the black grout that doesn’t dry.
Thank you, Michelle
Hi Michelle,
What brand of grout was it? If it was polyblend then your problem is likely efflorescence, which causes the grout to turn lighter or white. It’s minerals on the surface of the grout once the water has dissipated. Sealer WILL NOT prevent your grout from getting wet, or turning darker when it is wet. It will ALWAYS do that. Take a drywall sanding sponge, or some sandpaper, and sand down the grout a little bit to see if the correct color is beneath the lighter portions. If so, you can get rid of that with an efflorescence cleaner.
As far as the darker areas, that is where water is draining behind the tile, it’s normal to a point. It just depends on where that point is in your particular shower. It should dry out within a day, if not there may be an underlying drainage issue.
Thank you Roger,
Not sure what kind of blend grout is, but the rest of shower floor dried fine. I’m going to have the drain pulled up to see if it’s a weep hole clogged bc it’s only around drain and up one 8 inch section to wall and it’s over 2 weeks and still not dried completely. I hope this is the right route to take.
Michelle
Roger, I was wondering is there a possibility of too much 511 sealer in the areas that aren’t drying. I do recall pouring sealer on tile and wiping around, waiting 10 min then wiping with a dry cloth.
Thank you, Michelle
Hi Michelle,
The sealer isn’t curing? It’s difficult to get too much sealer on it, any excess would easily buff off.
That would be the right place to start.
Thank you
Hi Roger
Pulled some tiles out around the drain, grout and set were damp after 3 weeks of no water on shower floor. There was also some black on outer drain and set( mold I think) . Weep holes are working so contractor letting dry for a couple days then removing some of discolored grout then going to retile and grout. Should I have him take out the bad grout and I can kill mold with bleach…let it dry out then have him tile and grout? Will mold spread if he tiles and grouts over it? Is it necessary to get rid of mold?
Thank you again Michelle
Hi Michelle,
Yes, it is necessary to get rid of mold. All bleach will do is make it white, it won’t kill it. The only way to kill mold is to completely dry it out, it kills the spores. If you have moisture after three weeks it sounds to me like there is no preslope under your liner.
Thanks again for all your help…
Hi Roger trying to send you a picture of shower floor without tile, not letting me send. Can you send me your email or a way to send the picture to you. Thank you
Hi Michelle,
Roger@FloorElf.com
I recently installed a one piece rubber membrane 7ft high along entire 3 sides of shower and 6 inches beyond the shower door location. I fastened it at the top and extended the membrane 1/2 inch into the top edge of the shower pan. I covered the membrane with concrete board & taped & seamed down to within 1in of the bottom of the shower pan. Water between the membrane and tile/concrete board surface is not restricted from draining into the pan provided the bottom 1 inch above the base is not filled in with tile adhesive. During construction I was very carefull to maintain the sqareness off all walls.My question is Will leaving out adhesive behind the bottom 1 inch of the tile for drainage and not installing grout between the bottom tile and top of the pan cause any problems. If so can I build up the adhesive on the bottom 1 inch of my tile and leave small vertical weep hole at the vertical tile joint location and grout the bottom tile/shower pan joint. Is it necessary to grout the above tile/pan joint.
Hi Bill,
If you are using thinset (which you NEED to use) it allows water to flow through it. It does not block water drainage. So you can fill the bottom portion with it, and it won’t be a problem. Do not grout between the wall tile and base (it’ll crack). You need to silicone that, but you don’t need to ‘fill’ the gap, it can be as thin as the depth of the tile, which still will not hinder drainage. And yes, you can also leave weep holes in that if you want.
What type of shower base do you recommend when tiling a shower? Any specific brand or store? Thank you.
Hi Barb,
There are a LOT of shower bases, and a lot of different types as well. Are you tiling the shower floor or using a pre-formed base. If preformed then they are all nearly identical when installed properly. If you’re tiling I prefer to fabricate my own from deck mud, but most all of them work well.
I am laying out the tile for the wall with the fixtures. Should my valve and diverter line up vertically with a grout line? If not, should they be centered in that particular row of tile? I am using 12×12 porcelain tiles and the width of the wall is 47″. I have a 16 x 20 niche on the side wall with a vertical cascade of mosaics which contain glass and travertine tiles. Should I consider another vertical cascade through the valves and shower head? I could send pictures if that would help.
Hi Jeff,
It doesn’t need to be any of those. Unless you are installing any type of accent that depends on it being lined up with the fixtures, the fixtures can simply fall wherever they fall. It doesn’t look unusual if they aren’t centered or lined up with anything. Lay it out based on the size and layout of your walls, not your fixtures.
I just finished a 48″ wide shower wall of drywall, Kerdi membrane and porcelain tile. AFTER I finished I saw your article about tearing out the plastic vapor barrier which was behind the drywall. I did not do that. However, since I put a 16 x 20 niche in that exterior wall I did cut an area of vapor barrier that large to fit in the niche. Is that opening in the vapor barrier going to be large enough to prevent the “mold sandwich” to which you refer?
Hi Jeff,
You should be fine.
Hi Roger,
I have a basement shower that is tiled with grout. Outside of the bathroom up against where the shower would be, it is drywall on the other side. Sometimes when we shower, we can see it leaking on the floor from the other side of the shower wall. It puddles up on the floor. It doesn’t happen all of the time. The length of the shower doesn’t matter. I have run it for a half an hour with no one in it and no water shows up on the other side. I guess my question is how can I found out where the leak is coming from myself and who could I call to help fix the problem. A plumber? A contractor.? It is such a strange problem, so I am at a loss. Any guidance would be appreciated. Thanks.
George
Hi George,
Your shower wall is likely installed with just backerboard (or worse – drywall) with no waterproofing on it. Backerboard is not waterproof, it still needs a barrier. Or your shower floor is improperly waterproofed. Leaks aren’t always consistent, they can be irregular. You need to contact a qualified tile contractor. A plumber can test the pipes and drainage, but it’s more likely in the tile substrate somewhere, especially if it’s inconsistent.
Roger,
I have a small window in a shower (inset 5″ & near the top of a 9′ outside wall to be covered with Hardi). It’s inoperable and has a 1″ wide fiberglass frame. The sill is 8″ above the shower head, & the shower doesn’t have a header. My plan is to tile the shower walls up to within 4″ of the window, & then trim out the window (& narrow strip of wall around it) with tile.
So, my questions are:
1) a) Should I seal the window sill, & part way up the jambs, & a few inches out onto the wall with Kerdi? My concern is that condensate will form on the glass & sill and make its way into the wall.
b) Or, should I seal all around the entire window (sill, jambs, & header)?
2) In any case, I plan to frame-out the 5″ deep inset with 1/4″ Hardi (frame is too narrow for 1/2″) and then tile it (with 1/4″ thick tile).
a) The sill is covered with a factory polypropylene sill pan (Marvin SillGuard) that’s intended to drain to the ouside. That’s great for outward drainage, but I now need to deal with inward drainage (from condensate). Note that the inward/outward drainage boundary is already well sealed. Also, note that this sill pan has ridges & a lap & is generally not a consistently flat surface. So, my plan was to put a 1/8″ plastic shim along the sill by the window frame, then cover (like a full-coverage smear) all over the sill pan with polyurethane caulk. then set the 1/4 Hardi into that while it’s still wet and screw it down. This gives an inward tilt to the Hardi, & fills the void between Hardi and sill pan—–which hopefully will eliminate a potential water pocket under the Hardi. Do you think this will work OK?
b) If I now cover the Hardi with Kerdi, do I have a mold sandwich issue with the Hardi (sealed on both sides)?
c) Is there a better way to do this?
1. I would seal all the way around the window – it’s still IN a shower.
2. Yes, it should work. No mold sandwich. Probably, but I don’t know what it is.
Thanks Roger. I’ll give it a try.
How should I handle the outside corners of the Hardi around the window? Do you still need a 1/8″ gap, then silicone in the gap, then alkali resistant mesh tape, then thinset——similar to inside corners?
That would be best, but not absolutely necessary. You can butt the backer on outside corners without problems.
1) Thanks, Roger. I will seal all the way around the window.
2) Regarding the mold sandwich (applies to bottom sill only):
The Hardi will be sandwiched between two impermeable layers. i.e. polypropylene pan (with caulk smeared continuously over it), then Hardi, then Kerdi.
Is this of no worry because the Hardi isn’t mold food, or because it’s unlikely that moisture will ever get there, or am I misinterpreting something?
3) How should I seal the Kerdi to the fiberglass window frame? Should I screed the Kerdi down on top of the Hardi, then leave the Kerdi flapping at the corner where it meets the fiberglass window frame, and then silicone the Kerdi flap to the window frame? Sounds tedious, and it won’t be in shingle fashion, but I don’t know how else to terminate that corner. (I’m assuming that thinset won’t stick to fiberglass—- it’s actually fiberglass with a factory coat of finished paint.)
2. It is not in a wall cavity, it is a small, single layer without an open cavity directly behind it.
3. Kerdi-fix the kerdi to the window frame. No, the thinset will not bond.
Hey Roger- Great website, and your explanations are easy to understand and thorough. My question is: Everyone talks about using roofing felt underneath the mortar bed in a shower pan. With a Kerdi drain and a topical waterproofer, wouldn’t this create the aforementioned mold sandwich? I’m thinking of stapling the metal lathe directly to the subfloor and pouring the pan without felt paper to allow airflow into the backside of the mortar bed. What say u, tile god?
thanks for your time.
Hi Brian,
You don’t need airflow on the backside of the mortar.
The tar paper is not there for waterproofing, and doesn’t need to go completely to the edges nor be sealed up. It is only there to prevent the plywood from prematurely sucking moisture out of your deck mud, which would weaken it. That’s all it’s there for. It will not create a mold sandwich unless you completely seal it like you’re waterproofing it.
Hi Roger, I plan to do liquid topical waterproofing of my shower walls. If grout is not waterproof, what happens to the water that gets between the tile and the membrane? In reading that I will need to silicone seal the gap between the bottom tile and edge of prefab shower pan. If you can direct me to where you might explain this. I bought the Liquid Wall Waterproofing Bundle. Thanks
Hi Bryan,
It runs down the wall behind the tile and into the base. When using a prefab you need to leave weep holes in the silicone line.
Regarding my shower: I have a concrete floor in which a type of membrane was put down and then tile was installed. My question : after removing the tile the floor is very damp. Its been about five hours since removal and no change. I guess eventually it will dry but what should I do to stop this from happening again? I don’t want a shower pan. I want to be able to lay tile on the concrete. Any help is appreciated.
Hi Jennifer,
That’s really vague. You don’t want a shower floor? What do you mean by that, are you replacing the shower floor with just a regular tile floor (that will not be inside a shower)? And what type of membrane? What color is it? If it will continue to be a shower floor you NEED a membrane in it. If it is a shower floor your membrane will always be wet – that’s why you need a membrane. You can not just bond tile to bare concrete in a shower floor, the water will soak into the concrete rather than go down the drain and will cause problems with your floor in the shower and around it.