Tile is NOT Waterproof

by Roger

A common misconception about tile and grout is that they are waterproof. Once you install tile in your shower you have a big waterproof box that will last forever. Ummm, no.

Tile and stone (as well as grout) will actually retain water. How much water it retains is directly related to the density of the tile. For instance, porcelain tile is much more dense than travertine. This means that travertine will retain more moisture and allow more water to seep through¬† to your substrate. If you happen to have travertine in your shower – don’t panic. As long as it was installed properly it will be fine.

So how do they figure this out?

When a specific type or brand of tile or stone is manufactured for production, the company will determine its density. There are four different categories into which each tile may be placed.

This is determined by weighing the particular tile, submerging it in water for a period of time, then weighing it again. The difference in the two weights determines the density or absorption of that product. Basically how much water it holds. It will then be placed into one of the four categories.

  • Non-vitreous: These are tiles that absorb 7% or more of its body weight. These are for indoor use only, normally on vertical surfaces such as backsplashes and wainscots.
  • Semi-vitreous: These absorb between 3% and 7%. These are also for indoor use only.
  • Vitreous: Absorb between 0.5% and 3%. These tiles may be used for interior and exterior applications.
  • Impervious: These are the most dense (porcelain) and absorb between 0.001% and 0.5% of their weight in water. They are suitable for all applications.


Depending upon where you intend to install the tile you may need to consider this. In most cases it’s not an issue. Only in the most extreme or unusual circumstance will you need to take into account the category of your particular tile. A tiled patio in Alaska, for instance. If you have a tile that absorbs a considerable amount of moisture and it freezes, well, you’re gettin’ a new patio.

The biggest factor to consider is the amount of water to which the tile will be exposed. (Along with the possibility of freezing, of course.)¬† For anything up to and including a regular shower, it isn’t necessarily an issue. These applications, using proper methods, should be at least water resistant before a box of tile is even opened.

Why is this an issue?

With any tile application, the durability of the tile will be only as good as what is beneath the tile! Let me say type that again – that again.

If you have a wall in your shower with just plain drywall and you stick your tile to it, it may look good for about a year. It may look good for much longer. But, if moisture gets behind the tile (and it will) through the drywall, to the framing studs, well, you’re screwed.

Your framing studs are (most likely) just simple 2 X 4’s. If even a minute amount of moisture from your shower reaches it all hell’s gonna break loose. Common studs will do what we call “wick” moisture. It is aptly named because it acts just like a candle wick (tile guys are simple folk).If you place one end of a candle wick in water the other end will be soaked in short order. Wooden studs do the same thing.

Think of it as a water highway. The water will simply continue along that same path until it finds something else to soak into. That something else is more wood. When wood gets wet it . . . wait for it . . . swells. Normally that swell has only one place it’s going – right against the drywall and into the back of your tile. Tile’s will crack, grout will crack, your patience will crack, and the end of the world will be right around the corner. You get the idea.

This is not (normally) a subject that needs to be considered when installing tile on your floor. A shower (or other wet area) is unique in that it is subjected to a great amount of water on a regular basis. Unless your kitchen is a swimming pool you really don’t need to be that concerned about it.

Just understand that tile and grout are not waterproof so care needs to be taken to eliminate as much moisture from the surfaces as is realistic in any given application. You know – don’t make your kitchen floor a swimming pool.

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Ryan

Hello Roger,

I really need your help. I noticed a crack on the grout of my shower floor tiles. I removed it and i also noticed that when i press on the tile, i could see water coming out from beneath the tiles. Is it ok that water can get under the shower floor tiles? What if there is a waterproofing membrane under the substrate? I am very worried that it might get into the wooden frames of the house if not properly addressed. Would it be ok just to regrout it? I really need an advise. Thanks in advance.

Sincerely,

Ryan

Reply

Roger

Hi Ryan,

If water is coming out when you step on it then your shower floor is not draining, the weep holes are plugged or something. If there is ANY movement in the tile something is incorrectly built.

Also, no need to ask twice, I get all the questions. That whole day job thing sometimes delays the answers, though. :D

Reply

Ashwini

Hi

We just shifted to new Apartment. we live on 2nd floor.Our son are continually splashing water out of the tub.Does it will cause any problem to downstair bathroom?like any leaking problem

Reply

Roger

Hi Ashwini,

Not unless he’s dumping full buckets of water out of the tub. :D If it’s just splashing 99% of that will evaporate before it reaches your substrate beneath your tile floor.

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Dennis Thweatt

Hi Roger,
Would you explain in detail grouting where the floor and wall tiles meet along with applying the silicone. Walls first or floors… your opinion and rational.
Thank you very much,
Dennis

Reply

Roger

Hi Dennis,

You don’t grout where the wall tiles meet the floor, it needs to be silicone. Perhaps I’m misunderstanding your question?

Reply

Ramon

Roger…HELP!!! I have committed to refinishing an outdoor mop area with a drain that is currently concrete. What is a suitable tile,grout and bonding mortar that will withstand near constant water and N.C. winter conditions? I want to provide a lasting and functional finish. I was thinking mosaic porcelain for ease of conforming to pitch to the drain but have no idea for mortar. I would think that epoxy grout is the best option for grouting. Any input would be GREATLY appreciated. Thanks…Ramon :eek:

Reply

Roger

Hi Ramon,

A porcelain mosaic 3×3 or smaller over ditra with unmodified thinset grouted with epoxy. It’ll outlast the building. :D

Reply

Nell

I’m thinking of putting a stone tile wall in my base there are no major water issues, but as you know basements tend to be damp. Any suggestions on material that I should use. Thanks.

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Roger

Hi Nell,

Not really, just be sure to set the tile with thinset. Moisture isn’t going to affect it at all, it won’t lead to any problems.

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Jenn

Roger,

My husband and I are remodeling our master bathroom. For the shower floor I wanted to use penny tiles. However our tile guy says do not use tiles that come on sheets (mosaic and penny) as they more surface area grouted then a bigger tile. He stated that after a few years it will look old, the grout would wear away, or it cause a leak. Is this correct?

Reply

Roger

Hi Jenn,

Grout will not wear away. Grout will not cause a leak. It will have more grouted surface on the area, but that in turn will give you more grip.

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Suzi

Hi Roger! Cannot tell you how many hours I’ve spent reading your posts since deciding to undergo a complete bathroom remodel on my own. Thank you for unselfishly sharing your expertise with all on the web!

My plan is to build the floor with deck mud and a wooden curb all over plywood and drywall, waterproof with kerdi membrane on the floor, curb and all the way up the walls. Ive selected a beautiful glass pivot shower door and a folding mounted bench and I’m struggling with the idea that when installed, holes will be drilled in my (hopefully) completely waterproof environment. Will that cause a problem in the long run? ALSO and just as concerning to me, I know pivot doors tend to drip a reasonable amount of water on the floor when opened after a shower. How can I keep the substrate under the tile floor just outside of the shower from rotting over time? :bonk:

Reply

Roger

Hi Suzi,

When the holes are drilled they need to be FILLED with either kerdi-fix (best) or silicone before the fasteners are installed. As the screws are driven into the filled hole it will reseal and open areas caused by the hole drilling.

You can use ditra membrane on your floor, which waterproofs it, or you can install kerdi outside your shower onto the floor before tiling it. Both will protect your floor.

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Suzi

Thanks! Can the kerdi membrane be attached to the Hardibacker on the floor?

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Roger

Yes it can. Unmodified thinset.

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Fred Mandryk

We have an outside patio deck 12′ x 26′ tiled with porcelain 5 years ago . It still looks great. It is installed on a 6″ cement pad which is the roof of the sec ond garage and attached to the house. We have water enterring dripping dowm through the ceiling ( Currently being channeled by plastic eaves trough). Any suggestions as to what can be done to remedy the problem.
Looking forward to any and al ideas.
Thanks Fred

Reply

Roger

Hi Fred,

Any leaking lies in your substrate beneath your tile. Is the deck properly sloped (1/4″ / foot)? Was the deck properly waterproofed or was tile simply bonded to bare concrete? Concrete by itself is not waterproof, it will soak in water and drain it out the bottom (which is why your driveway looks wet when it rains, until it drains mostly out of the bottom of the slap – it’s not evaporation for the most part).

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Nancy

We have a Sterling corner stall shower where mold has been growing in the floor caulking outside of the shower in the corner where the bathroom wall molding meets the bullet tile and the outside of the shower pan. This corner is wet to the touch and the mold has gotten worse over time and has expanded in both directions. Could this be a leak from the shower pan or from behind the shower tiles or caused by something else? Should we cut a small hole in the drywall next to the outside bullet tile to see if mold is growing inside the walls? The shower door has also leaked for many years, but this leak does not seem to be related to the mold growing in the corner outside of the shower. Would appreciate any suggestions. Thanks!

Reply

Roger

Hi Nancy,

Yes, it could be a leak from your shower, it could also be from the leak at the shower door. Drywall is like a sponge, so even though you may see water on the floor the drywall can suck it up into the wall just by coming into contact with it. Have you checked to ensure you have open weep holes? They are imperative to the proper operation of a shower.

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Nancy

There are no weep holes, and the shower has leaked out the door onto the floor ever since it was installed 9 years ago. We have never figured out how to stop this. The moldy outside corner of the shower is a newer problem that started long ago with cracked, wet caulking. Today, I determined, after my shower, that it is probably from a second leak, not caused by the shower door leak running down to the wall. Outside of the shower I inserted the edge of a paper towel inside the horizontal metal crevice that sits on top of the shower pan edge. The area from the leaking door to the corner was dry, but the paper towel was wet at the moldy corner. Any suggestions on where to go from here?

Reply

Roger

I would perhaps resilicone all the sealant in the shower. There could be a bead that has come loose. After nine years it’s actually way beyond the time for replacement.

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Nancy

Have re-siliconed a few years back, but will try again, especially in suspicious corner. Need clarity on your last sentence–is your suggestion that it is time for silicone or to do complete shower replacement? I would choose shower replacement, but I am a renter trying to help my landlord understand the problem. I am still confused on how to discover/confirm if there is a problem behind the tile and what to about it. Many thanks, Roger, on your willingness to help me sort this all out!

Reply

Roger

I meant time for replacement of the silicone. Usually every 5-7 years.

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Devin

Question. I am working on a tile shower. I am doing a mud/membrane pan with cement board for the walls.
First, do you prefer a liquid membrane on the walls or plastic behind the backer board?
Second, we want a white subway tile on the walls. Everything I have been finding has water absorption of 7%, Is that okay for shower walls?
Third, If I use a membrane do I put it only on the walls, not the floor?
Fourth, We are going to have a drywall ceiling. Do I tape the corners between the cement board and the drywall ceiling? Thanks

Reply

Roger

Hi Devin,

1. I prefer liquid over a barrier.
2. Yes, if your shower is properly waterproofed it’s just fine.
3. If you are using the mud/membrane pan then it just goes on the wall.
4. Yes.

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Tracie

I recently purchased a house that the previous owner did a lot of bad diy projects. One of them is the master shower. I do not think they used a shower pan and some of the floor tiles are actually loose. Obviously, it is not sealed as is. I know the best option is to have it ripped out and redone correctly, but I just don’t have the money for that. Is there any way to seal the floor and up the walls? Btw, it is on a concrete slab.

Reply

Roger

Hi Tracie,

Read through this.

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Ann

I recently had a tiled shower installed for the first time. After I take a shower, I squeegee the walls and the floor, and I also towel dry both. But, the grout at the base of the walls is still wet after 24-30 hours. This means that if the shower is used every day, the grout at the intersection of the walls and the floor will never completely dry out. Is this normal? How long should it take for the grout to dry?

Reply

Roger

Hi Ann,

Is the floor of the shower tiled as well? If not, it may just be a lack of weep holes. Regardless, the bottom of the tile should be siliconed, not grouted, to either the shower base or the floor tile.

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Ann

Yes, the floor is tiled with mosaic tile. All of the tile was grouted (sanded), not siliconed. Are you saying that silicone should be used only where the wall meets the floor or for the entire floor as well?

Reply

Roger

Only where the wall meets the floor. Any change of plane.

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Ann

So if I scrape out the grout where the wall meets the floor and use silicone caulk instead, the new silicone seam at the change of plane will be more waterproof than grout. But since the mosaic tile floor also has grout between each small tile square, the floor will still not be waterproof. So, what difference would it make to waterproof the change of plane if the floor itself has grout which isn’t waterproof?

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Roger

Ann, you seem to be confusing a couple completely different things here.

1. Silicone at changes of plane are NOT for waterproofing. It is purely aesthetic. You need to have expansion space at all changes of plane. If you fill those open spaces with anything it needs to be flexible. That’s it.

2. Yes, water will get through your tile and grout on the floor, and the walls, and anywhere else you have tile that sees water. Your waterproofing is UNDER your tile, in, behind, or on top of your substrate. Your tile, grout, silicone, etc. has absolutely NOTHING to do with waterproofing anything.

If you are doing all this in an attempt to make your floor waterproof it isn’t going to work. However, you stated that the ‘grout at the bottom of the wall remained wet’. This is indicative of either the floor/wall connection being plugged up with grout (most probable) or your weep holes in your drain at the bottom of the shower being plugged. Once you remove the grout and silicone just the depth of the tile (not FILLED) it should be able to drain down the wall and under the tile on your floor and into the weep holes at the drain.

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Ann

Now I get it – that the water is supposed to get through the tile and floor grout.

Perhaps that explains why the grout between the mosaic floor tiles darkens in places (not evenly, though) when the shower is used regularly.

If the shower remains unused for long enough (weeks), the darkened grout between the floor tiles returns to its original lighter color. Is this normal? I am assuming that by not using the shower for a long time, the grout lines are drying out and that is why they return to their original color. Is this typical, and to be expected?

Reply

Roger

Hi Ann,

That’s exactly what’s happening. However, if it is the tile around the drain then perhaps your weep holes are not working correctly. The shower should drain and dry out within 24 hours, normally much more quickly than that. But yes, it is normal.

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Ann

The tiles that are darkened are near the walls and sort of unevenly dispersed in other areas of the floor, but not so much near the drain. It takes a long time (3-4 weeks) for everything to dry out completely, and for the grout to return to its original color, it seems.

As you stated earlier: “Once you remove the grout and silicone just the depth of the tile (not FILLED) it should be able to drain down the wall and under the tile on your floor and into the weep holes at the drain.”

I am assuming that you mean at the changes of plane only, correct? This seems to be the solution to helping the shower floor dry out quicker. Right now, it takes 3-4 weeks before the grout color returns to normal. How do I scrape out the grout between the tiles at the change of plane without damaging the surface behind them that is providing the waterproofing underneath?

Reply

Roger

Yes, only at the changes of plane. Get a grout saw and take your time with it. You’ll be able to tell when you’re getting close to the substrate.

Thuladu

Hello Roger
I have a problem whereby a pipe bust in my bathroom and water were all over the house and now my insurance company doesn’t want to fix the tiles, they only want to fix the wooden floor because they say there is no way tiles can be damaged by water but I did told them that water were on the tiles almost the whole night. Now the tiles are lifting in the other effected areas. how long can it take for tiles to be effected by water. these are the tiles which are in the dinning room and the bedrooms.

Reply

Roger

Hi Thuladu,

They are correct, the tiles will not be affected. However, the wooden substrate beneath them will be affected which will compromise the installation, and they damn well know it. Tell them you don’t need the tiles fixed, you need the underlying substrate repaired, the part that WAS affected by the flood.

I hate insurance companies…

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Anne

Roger,
We have a recurring issue that is in need of being addressed with the builder again. We had our entire downstairs renovated three years ago. We had an open shower installed and it had the cool drain that is long and “hidden” with tile (trough drain). After about a year and half my husband and I began to notice a lime looking build up on many of the edges of the tile and on the grout lines on the floor of the shower. WE tried to clean the shower with the recommended cleaners but it didn’t come clean. We got the builder to come and look and he got the owner of the installer to check it out. They couldn’t really decide what the problem was. My husband and I suspected that moisture was coming up from underneath. They didn’t think so… They had a worker come out and clean the area with machines and acid… Then they resealed. That was about 4 months ago. We are noticing that the hazy lime look is beginning to return… What do you think could be causing this problem? Thank you for your input! Anne

Reply

Roger

Hi Anne,

It sounds like calcium buildup to me. Do you have really hard water or well water?

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George

Hi Roger,

We just purchased a house and it has a walkin tiled shower downstairs. It showed a high moisture on the outter wall so I opened it up. The tile pulled right off and i can put my finger through the aquaboard. I noticed they have a layer of thin plastic between the aquaboard and the studs. Is that common practice and how can I tell if I will have to reframe it?

Thanks!

Reply

Roger

Hi George,

I have no idea what aquaboard is, but if you can put your finger through it then it shouldn’t be in your shower. Yes, a plastic barrier between your wall studs and substrate is a perfectly acceptable method, but your substrate needs to be cement backerboard for it to be effective, otherwise you’re just going through the motions of waterproofing.

Reply

Christa Nichols

Roger- My husband and I moved into a new home (April 2014) with a carrara marble shower in the master bath. Almost immediately we noticed a waterline forming in the shower at the base. It follows the area where the pan meets the wall. We had water removal specialist come out to measure moisture levels and the tiles below the line are saturated but the tiles above the line are not. We were told that water is sitting behind the tiles thus causing the waterline. Our builder tells us that this is “normal” to have water behind the tiles and the walls are protected by the pan and also blames the porous nature of white carrara. I have seen many white carrara showers and never one with a waterline. Should we be concerned about long term issues?Should we pursue getting the pan re-done or should we live with the waterline? thanks for your feedback

Reply

Roger

Hi Christa,

NO! You should not ‘live’ with the water line. It sounds to me as if the weep system (weep holes in the drain) is not working correctly (plugged). You did not say how the shower was constructed, but that is the most common reason for water behind the tile not draining properly. That, or if your floor tile is NOT saturated at the same level as the wall below the water line, there is a sealant blocking your wall waterproofing transition at the bottom of the wall, not allowing water down under the floor tile to the weep holes. Common when a ‘bead of silicone’ is placed at the wall bottom, for some ungodly reason like ‘saw it on the diy channel’. :D

Reply

Richard

We are redoing our master bath and want to use slate tile in the shower area. Is this a bad idea? If not is there anything special we need to do with the slate verses a porcelain tile.
Thanks
Richard

Reply

Roger

Hi Richard,

Not if you use REALLY good slate – and I mean the stuff that’s 15-20 dollars a square foot. Short of that you oftentimes end up with slate which is little more than pressed mud. I would recommend finding a porcelain tile that looks like slate – you’ll be much happier.

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Mark Wilson

Hi Roger,

My exterior tiles laid last year has lime leaching through the grout and silicon in places which I clean by light scraping.
Once cleaned looks great but the issue return after rain.
Could this be an issue the quality of the tile adhesive use?

Thank you Mark from NZ.

Reply

Roger

Hi Mark,

It could be a number of things. The quality of the tile adhesive may be an issue, it may not. Do you have a membrane of any sort beneath the tile or is it just bonded to concrete?

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Onil

Hi there, Roger. I built a concrete pond recently and painted it with epoxy. The water seems to seep out still in the concrete walls. My last resort will be installing ceramic tiles and will be using silicone sealant as grouting. Would that work? I’m going to scrape the epoxied walls with an abrasive so as to have the tile adhesive something to hold on to. Am I crazy, because I’m hopeless at this point. Talk about nightmares huh? :(

Reply

Roger

Hi Onil,

I don’t know what type of epoxy you painted it with, unless it was specific for waterproofing (I don’t know of any product for that which is epoxy) then it likely won’t waterproof it. I would get a product like redgard and paint it over the epoxy, that will waterproof it and the thinset bonds directly to it for the tile. Do not use silicone for grout – use grout for grout. :D

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Gabby

Hello Roger,

I plan to redo the shower floor and walls. I don’t know which type of tile to purchase. The shower tile I have right now must of not been installed properly since some of the grout is coming apart and I see moisture on my sheet rock. Any ideas…

Reply

Roger

Hi Gabby,

Porcelain is normally best in a shower, but nearly any tile can be used. If installed over a proper substrate the type of tile is rarely an issue at all.

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Shawn

Hi Mr or Mrs Floor Elf,
I read your article “Tile is NOT waterproof.” I found it very informative and interesting.
I have a problem with a house that I am buying and I cannot figure out a solution.
The wood floors in the family room are buckled. The seller says the wood was not properly installed and that she has been living with it in that condition since 2003, my gut tells me there might be some moisture. The house was build on a cement slab in 1978 in Los Angeles hills. I think there might be some moisture coming up from under the slab.

My questions is, if I tear out the wood floors and install tile, will that solve the problem?? Travertine??

I plan to use wonder board and insulation under the tile to act as a barrier. My wife thinks there would be mold build up underneath, but I don’t see that happening.

Would love to hear your thoughts.
Thank you in advance.
Anxious home buyer.

Reply

Roger

Hi Shawn,

You can not use wonder board on concrete. If you have moisture coming up through the slab I would use a product like ditra, which has vapor dissipation channels built into the underside of it. This will allow any moisture from the slab to evaporate and dissipate beneath your tile installation without affecting the tile itself.

Reply

Carol Ann

Roger,

I have been thinking about doing tile in my entire bottom floor on my two story home (not a basement). I love the look of the tile. I foster dogs. I had some fosters that found a spot in my dining room and urinated on the carpet, now all other dogs find that spot and mark it also. I have cleaned it to no avail. Would you recommend tile? Is there a way for me to water proof the grout? Since I foster the dogs it is very hard to predict who is house broken and who is not?!?!

Reply

Roger

Hi Carol,

Yes, tile would obviously be a better solution. You can use epoxy or urethane grout rather than regular cementitious grout.

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Pat

Because of two, “100 year” floods, we have replaced the basement flooring twice in six years in our raised ranch. Now we are going to install porcelain tile down there. We NEED the living space. In the meantime our adult children are almost at war over the “temporary” living/sleeping arrangements.

Anyway, the tile I’m looking at is a faux wood plank style from Lowes. For the best look we will want very small grout lines. What’s the best grout to use (sanded/unsanded)–and do you have any other tips on how to make this the LAST floor we install for a very long time? We are first time homeowners and novices at all things DIY.

Thanks!

Reply

Roger

Hi Pat,

Grout line size depends on the tile consistency. 1/8″ is doable, but you need to take your time with it. If you use a good membrane beneath your tile, like ditra, if it ever floods again the floor won’t be affected by it.

Reply

Pat

Hi again, Roger.
You brought up the membrane; I had assumed that in our situation it would be better to use none. Here’s my thinking: the less there is under that tile the less chance there is for moisture (and possibly mold) to become trapped anywhere if we ever have groundwater issues again. So my intention was to install the tile directly over the concrete floor (my bro-in-law, a young carpenter/contractor will be doing the actual installation). But you think we should definitely use the membrane? That wouldn’t increase the chances of water getting trapped in the layers below the tile?

Thanks again for your help!
Pat

Reply

Roger

Absolutely you need a membrane. It guarantees that any water inside the shower makes it’s way into the drain where it belongs.

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Pat

Sorry, I may not have been clear; it’s not a shower, just a floor in a raised-ranch basement. A floor which tends to flood occasionally when the water table rises (during Noah-esque spring rainy seasons).

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Roger

Oh. :D In that case you can go directly to the concrete. Sorry, I’m in shower mode right now. :D

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Pat

Thank you! :wink:

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Julie

Forgot to mention that the grout appears to get wet only sometimes when the shower is running, but not always. It also appears wet when the shower has not been running.

Reply

Roger

Same answer. :D

Reply

Julie

We have ceramic tile in our shower and on the bathroom floor. Water is seeping through the grout on the floor tiles just outside of the shower pan. What could be causing this?

Reply

Roger

Hi Julie,

An improperly waterproofed shower floor.

Reply

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