mca330

Can I use my concrete slab as my shower floor?

mca330
August 18, 2019

In our new construction home I’m having stained concrete floors throughout the entire house. They will be sealed. I’m wondering, in my master shower, could I just leave that as my shower floor? I’d really like to do that there’s no lip going into the shower. If so, around the edges of the floor where it meets the wall (walls will be tiled) how can I seal the space there to make things waterproof? My sheetrock guy used the rock that is waterproof but there’s a small gap at the bottom. I’d really like to tile the walls and leave the floors as the stained/sealed concrete but I just don’t know how to keep the water from getting under the edges of the walls. Anyone know a solution?? Thank you. Melissa

Comments (59)

  • mca330

    With some of the comments I’m thinking I may not have explained my house very well. This was something I wanted to do from the beginning so I had the original slab slopped towards the drain. The shower area is huge. It’s 7 1/2 feet wide by 9 1/2 feet deep. The far end is where the freestanding tub will sit. The shower comes out of the wall on the left after you walking inside. The front part will have glass with a door. Seems like water proofing the slab shouldn’t be too hard. When I say the walls will be waterproof or that I’ve used “waterproof rock”, I’m referring to the fact that the sheetrock in the shower area is the type that’s meant for shower areas. It will then, of course, be sealed and tiled like any other shower. My only concern is that space between the floor and walls and the room is so big it’s really only an issue in the general area where the shower part is. Wondering if there’s some sort of “L” shaped trim or metal that could be used around the perimeter and sealed the floor. I don’t know what I’m thinking just trying to think outside the box. BTW, if you can’t tell by now... we don’t have a builder / contractor. We’re it. Does that description help spark any new ideas?

  • GreenDesigns

    Get an expert. It’s not that you are t describing it well, it’s that there is so much wrongness here. You don’t know what you’re doing.

    There is exactly 0 amount of any Sheetrock that belongs in a shower. To do a shower like you want, you wouldn’t slope the slab. You’d recess it 4“-6”. Your wet area is way way too large, so deeper would be better. Because, 1/4”/1’. Then your tile pro builds a proper preslope to the 2-3 drains that this will require, which I bet wasn’t done, and waterproofs it and the walls, with a topical membrane. Then you apply your final finish material. It will have a capillary break between it and the adjacent concrete, so nothing wicks anywhere.

    This huge oversized 63 foot shower thing is a 25K-30K shower. It’s 4x larger than a nice sized 48”x48” shower, which would run you +-7K. Especially by the time your tile pro corrects what has been done incorrectly and starts over, and manages the slope correctly to work with a tub not molding to death underneath. You’ll need to cut the whole slab out and run new pipes. That redoing the rough ins by a licensed plumber is not included in that figure.

    Theres a heck of a lot more technical knowledge to be able to design or GC a house than picking out pretty paint colors and worrying about it’s decor. You need an GC if this is symptomatic of the rest of the build. There’s a lot of things to double check now.

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  • functionthenlook

    My dad built a concrete curb around the shower. Then extended the tile down the wall and the concrete curb.

  • smileythecat

    Don't do anything more until you get some eyes on this project that knows the process, that's what you should take from this thread.

  • M

    You absolutely can have a huge shower. In fact, you can have a "whole room" shower if you want to. Those are common in Asia. They do wet bathrooms all the time. In a way, it's just a glorified zero-threshold shower that extends into the room; and American contractors do know how to build those.


    But it's more complicated than just having a concrete slab and some magic transition piece at the walls. You actually need a contiguous membrane that covers the entire floor and then goes up the walls. In some situations, you can get away with not going up all the way to the ceiling. But you still need to make the membrane from one piece between floor and (lower part of the) walls. The connection to the drain is also an issue. But various manufactures have good answers for that. Schluter, in particular, has a pretty solid solution.


    If you then want everything to look as if it was the same concrete that you use in the rest of the house, you could of course put a thin layer of concrete on top of the membrane. But, as others have repeatedly told you, that's something you must plan ahead of time. You can't really do this with the existing slab. You either have to already have recessed the slab, or you have to build up -- and that gives you the traditional threshold into the shower.

  • live_wire_oak

    The situation that you describe is a design that was built to use a curbed shower with a waterproofing membrane and tile. There are many concrete looking tiles out there. Find one that has a mosaic.

    To do anything else requires cutting out the slab for a repour. You can not make what you have be both curbless and concrete appearing. Not without building up the rest of the bathroom height with a microtopping over that waterproofing, (tied into the waterproofing NOT drywall on the walls) and then sloping down to the drain. That creates eight at the threshold instead of the shower curb.

    What size are your drains and how many are there? Your shower will need at least 2 2” drains. If that doesn’t exist, it all has to be cut out and redone anyway. You can not have one drain for that size space. Plus the tub drain needs to be located far enough from any wall so as to allow cleaning. Unless you are doing a drop in or under mount tub. That would be the better choice.

    What are your plans for additional room heating? Ventilation? Both will be needed, and act at cross purposes to each other because of the extra large space. Smaller showers hold in the heat and steam. That keeps you warm. The size you are doing can’t do that. It’s too much volume of air. Air moving across wet skin chills you. Adding heat will get a lot of it exhausted. You can’t not have ventilation though. Not with that much wet area. Underfloor radiant heat would be ideal in this situation. There are ways to be able to do it in a wet area, but again, it would to have been designed into the overall plan.

  • PRO
    RES 3d Sketches

    "the sheetrock in the shower area is the type that’s meant for shower areas"

    "Sheetrock" is USG's tradename for its gypsum board products. USG and other manufacturers might still make a moisture-resistant gypsum board (often called green board) but it was responsible for so many failures that they no longer recommend it for showers and the International Residential Code prohibits its use in a shower:



    I stopped using it in the 80's.

    This kind of gypsum board must be covered with a waterproof membrane in order to be used in a shower.

    Get a knowledgable person to assist you before you go any further.

  • mca330

    I’m definitely going to get a local contractor involved after reading all of your comments... more than just my “tile guy.” Sounds like I may have to give in and have a little bit of a lip going into the wet area by way of pouring another topper on top of my slab... something that transitions up the wall or over a membrane that does. I’ll let you all know how it goes... thank you for the advice.

  • robin0919

    GD......where in the WORLD do you get pricing from 25-30k for a SHOWER????????? That's 'insane'!!!! Sounds like you might be in LA or SF where house prices are 'insane'!!


    OP......ck out these web sites. It looks like the concrete base of the shower edges are raised.


    https://www.bing.com/search?q=concrete+floor+for+shower&qs=SC&pq=concrete+floor+for+showers&sc=1-26&cvid=D0DB7BFB51164188A9A3DB9C27C9D01D&FORM=QBLH&sp=1

  • BT

    GD......where in the WORLD do you get pricing from 25-30k for a SHOWER


    The 20k -25k range here is pretty common. The worse about that many custom showers failed few years later... When we were building couple of contractors gave me references ... called them and showers really failed few years later. I did not trust any contractor with the water proofing...



    Here the typical detail. It you already have similar detail, in slab membrane extending out and the two stage drain may be.


  • arcy_gw

    If you planned from the beginning then yes the end result is possible. You need to have a contractor who knows what all is needed involved. If you had this planned and told your builders and they have't prepped for it then you have issues, and a reason to have them start over. The cement will be slippery...have you researched the success of this by others?

  • millworkman

    "GD......where in the WORLD do you get pricing from 25-30k for a SHOWER????????? That's 'insane'!!!!"


    Yep, definitely insanity.......................

  • deb s

    This is THE guy to contact re decorative concrete etc maybe he can refer you to local source - his working is stunning and does showers https://concreterevolutionllc.com/our-team

    https://concreterevolutionllc.com/showers/

  • GreenDesigns

    I know I shouldn’t even respond to our resident exclamation point!!!!!!! But. When the typical shower size is 10-16 square feet, and costs 5-7K, and the proposed shower is 4-6X as large as that? 30K would be on the bargain side. It requires multiple pre-slopes to multiple drains. It requires engineering a microtopping on top of the waterproofing system that will have the appearance of the surrounding concrete. Just the waterproofing materials alone on this will be 10K. The plumbing fixtures themselves will also be 10-15K when you include the tub and all the valves from a quality brand. If anyone would do the labor for 10K? That’s so low as to be suspect of their abilities. I think I need to revise the estimate upwards. 30K would be too close to the bone to do this. And it doesn’t include a dime of the ancillary costs to do this.

    Something like this is in the ultra luxury category. It requires involvement from top end trades. It isn’t DIYable from someone looking to save money and be a GC for a day. This whole build is immediately suspect as to the important behind the scenes details that keep a house standing and waterproof.

    Someone didn’t understand that they didn’t know what they don’t know before they bit off way more than they could chew here. It goes beyond an incorrectly built and underpriced shower.

  • PRO
    Patricia Colwell Consulting

    I agree get someone in there now to do this right before all the money you spend will be for nothing. These things need to be planned from the beginning

  • PRO
    Jeffrey R. Grenz, General Contractor

    Reinventing the wheel on a DIY project is like jumping out of a perfectly good airplane without a parachute so you can check if your shirt creates lift.

  • PRO
    Virgil Carter Fine Art

    Seems the answer is pretty clear...


    Looks like the OP left the building.

  • mca330

    Virgil, I’m still here. I didn’t leave the building. I asked a question and you guys kindly answered. There is no such product to do what I was hoping to do. So I sought out a licensed professional today (as also recommended) and he is going to give me a price on 2 different options. One is to basically build a shower pan/floor on top of the slab and tile it. It would have all the appropriate layers and whatever runs up the wall under the durarock. It would mean having to forego the zero entry I wanted and have about a 4 1/2” step up / curb going into the shower. The other option is to basically do the same thing but to grind the hell out of the current slab and lower it so that when the shower floor is done correctly it will be zero entry.

    I asked... you recommended and I’m taking your advice. I’ll stay in touch to let everyone know the option I choose, the price and I’ll show the results.

  • PRO
    RES 3d Sketches

    Now it’s Durock instead of Sheetrock?

  • just_janni

    It appears the OP made a fair benign misstatement about "sheetrock" as a generic name for wall board (as a tile substrate or as gypsum board...) I am sure that this innocent error isn't enough to decide he's a walking disaster area.

  • PRO
    RES 3d Sketches

    Sheetrock is USG's gypsum board line. I was concerned that the OP was using a gypsum board substrate which is not suitable in a shower without a waterproof membrane added. Durock is USG's cement backer board which is suitable in a shower. Why use these terms if you don't know what they mean? The thread is a waste of time.

  • PRO
    Jeffrey R. Grenz, General Contractor

    @mca330 My apologies for the snark, but typically a DIY OP will shop for the answer they want for days if necessary. Applauding your decision and listening ability.

  • robin0919

    Mill.......you're definitely insanity. Sounds like you love to get ripped off or......... make ALLOT of money!!!!!!! Probably the money. That's what it's all about.

  • mca330

    RES... because I’m NOT a Pro such as yourself. I came here for advice. I think I said it’s “like” sheetrock but it’s the stuff that goes in a shower.

    Here’s the thing, I realize I could have paid a builder to build this house, but I wanted to do it myself (sub it). Have I made some mistakes along the way? Sure I have. I know that’s part of it. But, I’m learning. I came here to ask the Pros their advice on how to remedy a problem. Once I found the sub I was comfortable with he told me the same thing. I just had not gotten that far and was trying to wrap my head around things.

    BTW.... I’m a she... :-)

  • M

    That's pretty cool that you are doing this as your own general contractor. It's also a little intimidating. I am always impressed with how much domain knowledge is required to do a good job in construction.


    The good thing is that there are so many excellent resources online these days. I find Youtube is invaluable in learning new skills. And so are forums such as this one.

  • mca330

    The product my contractor is using is called the Schluter system. He said he’s used it many times and not his most favorite but considering my situation, it’s the best choice.

  • M

    My contractors always said that they believe Schluter is one of the best systems out there. It's a very comprehensive system with different components for pretty much everything you could need when building a shower.


    But it's not cheap, and it takes a little longer to install. It also is possible to mess things up, if you haven't been trained to install it properly. Look on Youtube. You'll find good videos explaining how all the parts fit together and how you have to make the transitions so that they are guaranteed water proof.


    It's a positive sign, if your contractor recommends something like Schluter instead of brush-on products. While there is nothing wrong with the latter, if used in the appropriate scenarios, Schluter sounds like a better fit for your more complex situation.

  • mca330

    He said he’s installed it several times and has been to their training seminars. However, he has a buddy with extensive experience using that product and he is going to bring him into the job and have him do it. He really sounds like he’s knowledgeable. I’ll take photos afterwards and post them. He started working this morning.

  • North Texan

    Take photos NOW, and keep taking pictures for every stage!

  • PRO
    RES 3d Sketches

    Yesterday, I advised you to "Use a Schluter or equivalent membrane system for the floor and turn it up the walls. " It can be installed over gypsum board.

  • robin0919

    mill.....I might have taken your response in the wrong way, if I did, I apologize.


    GD....those price are INSANE!!!!!! You must be in CA or NE where they are UNION!!!!!! The prices you are insinuating are for a 'kitchen' NOT a SHOWER!!!!!!!

  • mca330

    Here is a “before” photo. As far as price... my contractor is charging me $4000 in labor to do everything... fix shower floor, all the tile in the shower and entire bathroom plus the tile in the tub/shower surround in the guest bath. I am purchasing all material all the way down to the particular blades he needed for grinding down the slab... Schlueter system (expensive), tile, grout, mud, etc. The tile I purchased was porcelain from Southeastern Salvage and it was $.88 cents/sf for the tile for the shower walls and $1.99 for the tile for the floor. Then in the guest bath I just did a white subway which was $2.19 sf for the regular ones and the bullnose trim ones were $2.19 each. Crazy for those being that much compared to the nicer ones I bought for the master bath. I guess, since they’re popular, the price is more. Overall I think I’ll be just under $2000 for material. So to fix my problem and have tile complete in both bathrooms for $6000, not too bad. I know my contractor should be charging me double. I am friends with his mother so he’s going easy on me. I’ll post more pics as we go...

  • eelh

    following

  • PRO
    Jeffrey R. Grenz, General Contractor

    @robin0919 @mca330


    Large showers will break the bank if you aren't careful. I build in No CA, where my costs are expensive but still less than the bay area.


    Client just doubled the cost of a shower (smaller than yours) to about $20K with slab sides and not to be named designer tile. Slab materials at over $40, designer tile at over $50 per foot. I'm sure someone could figure out how to spend more.

  • mca330

    Wow!!! Well, I live in a small town in Alabama. I’m sure my exact shower and entire bath could and should be costing more, but I have bargain shopped for tile, light fixtures, faucets, etc. But, thankfully, still no where near that kind of expense. I’m hoping to keep my whole 2200 sf house to a budget of $220,000.

  • PRO
    Jeffrey R. Grenz, General Contractor

    At this point you should know within a few % the minimum total so you can make decisions.

  • GreenDesigns

    4K in labor plus Alabama equals water damage and a waste of 4K of Schluter used incorrectly. Especially around the tub penetrations. If he isn’t doing the whole bath floor, plus 6” up those walls, and all of the shower walls, he isn’t doing it correctly. The penetrations and the drains are going to be the problem areas.

    Contact your local rep for Schluter and take a zillion pictures. Send them to him. Especially the seams, corners, and penetrations. And the drains.

    Im assuming you already have a copy of his contractors license and insurance policy? And the plumber’s who he will have to work with closely in this? And have called the insurance companies for verification?

  • millworkman

    What is the tiler contractor putting over that purple drywall for waterproofing?

  • M

    I purchased was porcelain from Southeastern Salvage and it was $.88 cents/sf for the tile for the shower walls and $1.99 for the tile for the floor.



    Make sure that the floor for the tile is extra grippy. They make tile that is suitable for showers, and it usually says so in the spec sheet. But if you just pick generic floor tile, you might be disappointed in the slip hazard that you created.

  • mca330

    Millworkman,

    He grinded the slab down lower and is installing the schleuter system. It’s a waterproof membrane made for that very thing.

  • millworkman

    I mean over the purple drywall on the walls..................

  • M

    Yes, Schlueter is great for this. I think what everybody is telling you is that you are much better off running a continuous membrane all the way from the floor to the top of the walls. You can sometimes cheat and run it up for just about a foot or two, and contractors like that option because it's cheaper. But wherever you stop having a membrane, you now solely rely on your tile and on substrate to be sufficiently water resistant.


    That might just be good enough. After all, a shower wall gets some moisture but it doesn't get standing water. And there is rock material that is more water resistant than mere gypsum board. But you are taking chances. And a potential future repair is essential a full gut job. So, over-engineering a little bit right now is money spent wisely.


    Also, Schlueter is awesome. But it only is awesome as long as it is installed correctly. In particular, this means that you must treat seams properly. And they must have sufficient overlap.


    No one accuses your guy of messing things up. But all of us have seen what happens if things go wrong. And it isn't pretty. So, everybody is extra paranoid. That's a good thing.

  • mca330

    I went by yesterday to check on my workers. They had the Schlueter system up and it went all the way from down in the floor to way up the wall. They had extra layers over the corners and seams that were on top of the other layer. I really feel good about it. They were covering it with the Schlueter mud in a pretty thick layer as they were starting the tile on the wall. On top of the membrane on the floor is another layer called Schlueter Detra (?). It’s thicker waffle looking stuff.

    I should have taken more photos but will do that today.

  • AJCN

    Take pictures everyday if you can. From all angles. Close ups and further back. Also take pictures of all The buckets of materials (like thin set), tools, rolls of Kerdi band, etc. etc.

  • PRO
    Creative Tile Eastern CT

    Quite the thread. Unfortunately some important basic information seems to have been overlooked.

    I) Gypsum board has not been allowed in wet areas since 2006.

    2) Schluter Kerdi membrane is not recommended over moisture resistant dry wall due to the waxy finish. They are ok with regular drywall.

    3) Adhering membrane to taping compound and paint. Big no no.

    4) Most Important - Drywall manufacturers do not want their products in a wet area period. USG makes drywall and a waterproof membrane far superior to Schluter Kerdi and they will not allow it installed over drywall in a wet area. Schluter and others say it's Ok. (Actually they are only saying they can adhere to it.) Funny how they think they can over ride what another product manufacturer states their products limitations are and consider it a acceptable substrate. What is getting overlooked here is possible condensation in the wall cavity itself. This can destroy the gypsum board from behind where cement board or a foam panel would not be affected. Perhaps a drip in the control valve, poor seal on the gasket or elsewhere will break that gypsum board down. Now you have no recourse as Schluter and others will say the shower system worked fine it's the wall which it is attached to that failed. mca330 I do hope none of these issues will occur on your project and all goes well. There are some such as myself that would have walked away or insisted all manufacturer instructions and proper methods involved in the shower assembly were followed. Best

  • AJCN

    OP, you should read the manufacturer’s instructions for yourself. You can also contact schluter directly and get the phone number for the area rep and call to see if they can visit the site or answer questions for you by phone. I did this in my Dad’s remodel when they were installing Denshild. I talked to the area rep because I thought tile pro was skipping a step. Tile pro disagreed; area rep agreed with me and had a “talk” with GC. I did the same thing when my tile pro was using Hydroban boards. I had a question and wanted to verify pro’s answer with the rep, which he did. The manufacturer’s don’t want their products used incorrectly; that’s not good for their business. I found the reps to be friendly, informative and responsive.

  • PRO
    Creative Tile Eastern CT

    We know the fastener schedule for drywall is 12" - 16" with added weight of taping compound and paint. Quite minimal.

    Fastener schedule for most cement board & foam boards is 8" with added weight of setting mortar, tile or stone and grout.

    How often was the drywall fastened? Do you have a photo? Is it fastened enough to support the weight of a tile installation?

    mca330 - Please don't take this as criticism. Simply pointing out facts. It's your home. Do as you please.

    If fasteners were not added prior to waterproofing membrane and tile there is a problem. The tough part is how will you know at this stage. Hopefully photos.

    Drywall screws can NOT be used as fasteners as the alkali in the setting mortar (which is used for the waterproof membrane) will rust them. Therefore the initial fasteners are useless. Is the problem getting clearer? The result would be a board held up on pins as there will no longer be any screwheads. It makes for a very easy rip out. Seen it many times.

  • AJCN

    mca330,

    I am not posting this link because I think your project has gone completely south, or it’s going to go completely south. I’m posting it because there might be some information in here that can prevent your project from going down the tubes; or if it does there’s some information in here that might help you to protect yourself.

    And the “going south” phrase is not meant to be insulting. I live in the south. It’s just a phrase people use.

    https://www.gardenweb.com/discussions/5725013/what-to-do-when-a-project-goes-completely-south#n=13

  • robin0919

    Jeff.........at $50/sf.......your client has more money than common sense!!!!!!!! Sounds like they won the lottery.......... or just plain stupid.

  • PRO
    Jeffrey R. Grenz, General Contractor

    One could say the same about almost anything as the US average home is about double world size and prefab showers are a few hundred bucks.

    I do show clients the numbers, but they want what they want. That's why there are custom home builders.

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