Is Your Shower Tile Really Waterproof?

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Subject: Florida Recessed Shower, Odor, Builder Did Not Use a Liner

Just wanted to get thoughts about a Florida recessed shower. I have odor, not moisture or mold. The odor is seeping through to the closet which abuts the shower. Could this be due to the fact that in Florida builders are not required to use liners on showers that are recessed below the slab. If so, does anyone know of the correct way to install a recessed shower????

Jerry Fish

Subject: waterproofing grout

Great article. I was waiting for the magic solution to making the grout waterproof. My new shower has one single slab granite wall and the rest ceramic tile, installed over a complete Schleuter kerdi system by a contractor. I think they were careful not to puncture the plastic floor to ceiling liner anywhere during later installation work. I don't know about the blocking, but do recall he did the flood test. They used a sanded Mapei flexcolor grout. I called the Mapei rep and he said it was "water resistant" but not waterproof and suggested sealing it. He did not have a recommendation for sealers to make it really waterproof. I note that most granite sealers focus on stain resistance and not waterproofing, though they do increase water resistance. The Mapei tech said their epoxy grout is waterproof.

The granite was sealed but not the grout or tile. After a couple uses, the granite looked like it was soaking up water at the base and got darker in a 3 to 5 inch strip. I figured water had got through the grout. I put a hairdryer on it for a couple days and the granite dried out. But I also got efflorescence through the grout in the wettest looking corner. That hairdryer was on high for a couple days so I'm hoping I got that initial moisture out. I resealed the granite and I'm looking for the best product to seal the grout. Ideas?


Subject: Shower mould

We have been blamed by our builder and landlady for causing damage to shower by not wiping it after every use. There was mould behind the shower and the builder came and removed not only the shower but also the bathroom sink and all the tiles, wall tiles and floor tiles, replacing the whole shower unit and putting the bathroom out of action for a week,
Is this a case of this builder covering up building errors and blaming the tenants?? Why would a leak in the shower require the removal of the bathroom sink? And does mould really damage showers to this extent??

Don MacAdam

Subject: Shower Base Construction

We are presently installing a shower base. We blocked in the existing studs with 2x12"s along the bottom plate. We installed a seat at the end and it is solid 2x12's with a seat back of 2x12's. We are not using a vinyl liner, rather we are using black construction felt and hot mopping the cement floor both under and over the felt going up the walls about 12"-14". The wall under the shower is also black felt hot mopped up about 36". We are also installing three ADA grab bars 37" off the floor. We blocked between wall studs with 2x12's in all four corners 37" high on center. We don't have a need for the ADA Grab Bars yet, but will in a few years.

David Sironi

Subject: Shower with Kerdi board and prefab pan leaking

About a year ago I redid a bathroom with shower. I did the plumbing and construction. I contracted for the tiling. Both walls and floor are tiled. a DeamLine Slimline shower base was used. Kerdi board and Kerdi flooring were used behind the tiles.

Last week I noticed the ceiling wallboard was wet in the bathroom below the new tiled bathroom. I have removed a portion of the ceiling to diagnose the problem. It seems that when water is directed onto the lower tiles of the shower, water begins to come down the joists that support that outer wall. The edge of the shower pan is over those joists. Recently the shower has seen increased usage.

Having read your 'how to' article I note:
1) I didn't block the pan with 2x10 between the studs (neither does the DreamLine install manual call for that blocking. )
2) I did not know that grout (nor tile) absorbs water. Is water passing through it to the backing?
3) does water wick up and over the edge of the shower pan and then down the support wall?

I'm about to call the contractor that installed the tiling and Kerdi board. He had experience with Kerdi board and the company out of which he worked sold the product. However, it was relatively new to them.

He may offer to put a larger bead of caulking along the shower pan where it meets the wall tile.

And, I suppose this could be happening on the second wall as well, but not as yet noticeable?

Any advice?

Tom Smith

Subject: Schluter Kerdi issue

I had no idea people were replying to this article!

The first thing I would recommend is to contact Schluter, 1-800-472-4588. They are very proactive with support.

The 2x10 blocking is not required for Kerdi Board installation. If the KB install is correct and wasn't compromised by an installer raking dried thinset out of a grout joint with a razor knife, water will not pass through the Kerdi membrane. Tile and grout do absorb water and water will defy gravity.

If you have any other questions, you can contact me directly.




Subject: Water marks around shower grout only days after renovation

After suffering through a painful bathroom renovation, we were happy to simply have a functioning shower.... or so we thought. Following using it, we noted water seeping through the divide between the shower and the bathroom floor under the saddle. Additionally, the grout at the base of the floor retains moisture a full day after last use.... I dry it with a hairdryer, and then watch as it darkens after I take the heat away.


Subject: infloor heating leaked into liner

I installed infloor (water) heating into my downstairs shower. I ran the lines inside the liner and then through the cement. I have discovered that my heating line at the junction to the shower has been leaking and putting water into the liner. It really smells in there. I have had it open for about a month but can still see a bit of water on the edge of the liner. Any thoughts about how to get it dry? Also what about putting some bleach in there to kill the smell and then try and suck it out? Thanks,

Randy Lofthouse

Subject: Waterproof Bathrooms

Great article. More homeowners need to be aware of just how important it is to plan accordingly. Always consult with a professional, and review which waterproofing system they will use and why. Personally, I trust Schluter Systems for our shower components, AND total bathroom waterproofing and uncoupling. This means that while a person is stepping out of the bath tub or shower, (potentially dripping water onto the main tile flooring), there is absolutely no need to worry about water making way to the wood-based subfloor via the grout joints and perimeter. There are many brands and systems for building showers correctly, and available within reasonable cost. However, in the United States, we still have a failure rate of 75% concerning tile showers and tub surrounds! Consult an expert, understand the process and feel great about your remodel.

Randy Lofthouse
Lofthouse Tile & Mosaic

Thomas S

Subject: How can anyone trust an install or remodel with those statistics

Reading this thread gives me no faith that a tile shower can be properly installed in the US. Of those 75% failures you speak of a significant percent of them were most certainly installed by professionals, which means professionals don't know what the are doing a good part of the time. How can anyone feel confident about the resulting install unless you are a professional yourself and know you are doing it right? The rest of us are likely shooting ourselves in the foot if the 75% figure is accurate.

Ryan Labbe from Affordable Tile and Grout

Subject: Brilliantly Written Article on Proper Shower-Base Construction

As a tile-contractor of almost 30 years, it sadden me greatly to see so many tile installers over the years not adhering to the proper building practices and techniques of ceramic tile/stone installations, especially in wet area's such as a shower-base. I get at least one phone-call a week from some weary homeowner with a leaky shower-base desperate for someone to provide a quick-fix which is impossible to do because of all the mistakes/shortcuts that were made from the beginning of the process. This article written by Tom Smith of Bluegrass Flooring was absolutely brilliant and dead on.

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From the wall street journal online:

"Etiquette and tipping experts agree that tipping a contractor and his employees isn't expected because contractors offer to do a job for you at a specific price. Any extra money they would want would be built into their bid. Also, it's a business relationship rather than one where they are performing a personal service for you like a waiter or a maid. But if the employees do extra jobs around the house, then experts say it is appropriate to tip a cash amount equivalent to the task; "tip gifts" such as cookies and drinks can count. "The key to tipping is whether or not it was outside the scope of what was normally expected," says Mark Brenner, author of "Tipping for Success!"

My opinion is that a little bit of courtesy (snacks, drinks, expression of appreciation etc.) goes a long way and upon completion of their work you feel compelled by a job well done to offer a little extra in the form of a tip - go for it, but do not feel obligated. 

I agree with Ben, as usual. First, test your slab - put a sheet of plastic over it, at least 3 feet square, taped down to the slab all around - leave for 3 days. If the slab darkens with moisture, or there is any condensation drops on the underside of the plastic, you have a damp slab. If you have visible moisture or moisture discoloration at any time during the course of the seasons with exposed concrete slab, then you have a wet slab. Even just a damp slab can put several quarts of moisture passingfrom the ground through the concrete into the air per day, and a wet basement slab in contact with wster at its base  can generate as much as 10 gallons a day of air moisture - which means that pretty much anything placed on it WILL get damp enough to mildew or mold.


For a wet slab, a polished concrete or epoxy/polyurea surface is your best bet. Any other surfacing you put over it is likely to mold. Ceramic tile with waterproofing additives in the mortar mix can work if the surface is properly prepared for good bonding, and you use "plastic" thinset and grout rather than cement based grout. Basically has to be done the same way as for a gymnasium shower floor or pool deck to work right.


For a damp slab, assuming it NEVER actually gets wet either from high water table under it in wet season, or from surface flooding from foundation leakage, then you have several options:


1) As Ben says, Pergo and others make totally plastic flooring material in a variety of surfaces that can be put down on a smooth slab over a vapor barrier and totally inorganic plastic padding - looks like bubble wrap commonly. Does not guarantee mold will not form between the vapor barrier and the concrete. IF you use a snap flooring version, can be taken up if it gets saturated and dried, then put back in. Not so with glued or nailed versions. Some people also use snap or interlock together rubber or foam flooring over a vapor barrier, particularly in rec rooms, which can be taken up easily in event of flood. 


2) A vapor barrier under an inorganic pad as above, overlain with an open-weave backing synthetic fiber (nylon, rayon) carpet with NO natural materials in it, which has lots of breathing space in the weave can work. I have used open-weave backing short-pile 100% nylon carpet from Armstrong in my basement for about 30 years, with vapor-barrier floor paint but no plastic sheet vapor barrier or padding and never a mildew problem, even though the plastic sheet test did show a minor amount of condensation. The key is a breathable carpet and decent airflow in the basement.


3) Any other type of flooring - laminate, vinyl, hardwood, etc will act to xxxx vapor evaporation, so risk mildew/mold under them. You can put down a sealer on the concrete and a vapor barrier and frequently get satisfactory service in a low moisture slab - generally only ones that are at or above surrounding ground level, but you always have the risk of mildew, and if ever flooded are pretty much trash. If you use a sheet product, use plastic, not organic - so vinyl, not linoleum, for instance. I have successfully done asphaltic based vinyl tiles and vinyl sheet using asphalt adhesive - the 1970's method - on damp flooring without trouble, but you have to make sure the concrete is VERY well sealed first with multiple penetrating coats of sealant placed on ground concrete surface so there is open voids for the sealant to penetrate, then let sit a week or more untouched and unwalked on before putting down the asphaltic-bonded tiles or sheet. The key is to make sure the concrete is less permeable to moisture than the overlying material. If you use a non-asphaltic adhesive (because of smell issues or allergies), then I would recommend full-adhesion waterproof mastic, not spot-adhered or glueless, so there are no air gaps under the sheet to accumualte moisture and mildew.


4) Of course, in new construction, if a full edge-bonded heavy duty plastic liner is put in the bedding sand layer UNDER the slab, that can turn a potentially wet or damp situation into a basically dry one, allowing almost any type of flooring to be used, though I NEVER recommend hardwood over below- or on-grade slabs. Of course, in a basement, one should probably assume that at some point it will get at least partially flooded from foundstion leak or pipe failure, so polished or stained or coated concrete, tile, or removeable flooring is the most likely to survive that.


5) Another option, in pretty much either case if your ventilation system removes the vapor as fast as the concrete can supply it, is padless thick open-weave area rug with a "Miller Weave", "Open Back", "Berber" or "Rag Rug" construction - which have lots of air holes in the rug and backing to let the moisture through. Then if getting damp or floods, just roll up and take out to garage and drape over some elevated 2x4's across sawhorses to dry out. Again, start with good concrete sealing first - preferably deep sealant with compatible epoxy surface coat to minimize water transmission.

I agree with your choice - this is about the only product that can realistically, for a large room, be taken out and cleaned up after a flood and reused, thouhg carpet can be if you strip it into smaller pieces to carry wet, AND you have somewhere to wash and dry it - that is usually the problem. However, bear in mind it still has to be done within about 2 days or mildew/mold will grow on it, and may or may not be totally removeable. My personal preferences - mostly because their products are consistent, the joints stay snapped together, and they are not overly soft (a problem with cheap vinyls) are Pergo, Tarkett, Armstrong. Whatever you buy, be sure it can come back apart - some plank products are not made with a self-adhering contact glue in the joints that prevent you from taking it apart again, and some brands their snap design, while maybe better at preventing joint separation, cannot feasibly be unsnapped without tearing or breaking it off. Also, be sure whatever brandname and product line you choose it 100% vinyl (other than the urethane surface protective layer) - many vinyl floor products have paper or fiber cores or other water-absorbing components. Remember that, on concrete, since it wicks soil moisture through it, you till need a 6 mil vapor barrier under the flooring and positively sealed all around the edges to avoid the risk of mold growing on the underside of the vinyl.
Agreed.  If you have existing cracking in porcelain you need to know the cause first.  I don't know of any reputable contractor that would dare install tile over existing tile.  Also, any manufacturer warranties for defects would be null due to improper installation.  Did the contractor offer this solution or did you ask for it?  The mear fact that he is agreeing to or offering it tells me you need to leave this guy for someone who knows what they are talking about before he does only half the job which will have to be redone in the near future, costing you more in the long run.

I get so many calls from customers that were talked into a "cheaper" way to do something only to find the work very sub-par.  The sad part is they are out the money they spent in the first place along with the additional amount I have to charge just to undo what the first contractor did before I can do it right.  This floor could end up costing you double what it should if it's not done right.

Todd Shell
Todd's Home Services