Grout is not waterproof and isn't meant to stop water!

I'm no expert, but it is probably a leveling issue, so you have some dips where the water is pooling and/or drain weep holes are clogged.

Could the water be getting in elsewhere but affecting the marble near the drain? For example, are the floor/wall joints caulked?

I have ceramic tile and had to have the floor/wall joint caulked to avoid dark spots in some tiles that are not next to that joint.

Thanks chispa, I assume since it's a very experienced tiler he didn't clog the weep holes, I am more inclined to think it's a levelling issue as I don't think he has done a ton of curbless showers.

Thanks socalgal_gw - the wall joints and floor joints were caulked. I think that if the grout joints were not fully packed, which they don't seem to have been, it's possible that there is more water getting through than is to be expected. But I looked at them pretty closely and caulked any fine cracks or pin holes. There were also a few small gaps in the walls, so water could have entered there and run down the shower liner, but I filled any gaps I found and I don't think any remaining leakage could be substantial enough for water to pool to that extent. The shower fixtures and chrome niche were caulked.

I am not a pro but did remodel fairly recentlyl with a marble tile in the shower.

It is hard to tell from your picture but the area immediately around my drain is noticeably sloped so absolutely no water ever collects around the drain. I have an excellent fan which turns on and off based on ambient humidity levels and the shower floor, curb, and shower glass are all dry almost immediately.

Thanks Helen - The drain area is definitely sloped but probably the same pitch as the general area, whereas my other marble shower pan slopes a bit more at the drain, so maybe that's one problem. I bought the moisture sensor fans for my other bathroom, this one was contractor spec so no sensor. But it doesn't make a difference if I leave it on for an hour or 5 hours, and it takes weeks to fully dry out. Even running a dehumidifier directly in the shower enclosure didn't dry it out quickly - it still took more than a week. The surface of the tile dries out normally. After 10 minutes or so all you see are beads of moisture waiting to evaporate and after 20-30 mins most of the tile is dry to the touch, so it seems clear that the moisture is being absorbed from below, it's just not clear how it's getting there or why it is pooling.

Thanks WizeOwl - There was no discolouration after the tiler applied his impregnating sealer. The discolouration began after the shower was used regularly. The sealer I used is a penetrating sealer made for natural stone and it allows moisture vapour transmission. If the sealer in general were the problem I wouldn't expect it to be discoloured only around the drain (unless you mean that without a sealer the affected area would evaporate more rapidly). Also, my other carrara marble shower pan gets at least two new coats of the same sealer every year and has never discoloured despite daily use. It is also a schluter membrane and drain.

As far as I am aware, this installation does follow the recommendation in the link you provided - it's a bonded waterproof membrane and a "very permeable (breathable) impregnator" sealer was used. But as I mentioned, the grout job was poor, so certainly not "near waterproof" and if the drain flange is causing a bit of damming, that could explain it. So maybe if the grout is redone there would be less water below, little or no pooling, and the sealer would allow sufficient evaporation of a smaller amount of moisture penetration.

Thanks for the link, I will send to the contractor to discuss with the tiler.

Question - what type of shower pan was used underneath your first marble tile installation where you’ve had no problems? Is it a traditional mortar bed - water in/ water out system?

Your current shower pan was built using a surface bonded waterproof membrane. The article linked by WizeOwl above was written by Pavlo Starykov. Mr. Starykov noticed a significant increase in the amount of discolored marble tiles in shower pans over the past several years. The discoloration is caused by water retention as you’ve already noted in your posts. Mr. Starykov decided to investigate the issue further - and set up experiments in order to determine the best way to avoid marble discoloration caused by water retention.

After making several model shower pans, Mr. Starykov concluded that the best way to install marble was using a traditional mortar pan - water in/water out system. Marble tiles + cementious grout do not prevent water from traveling underneath the tile. A traditional shower pan is specifically constructed to deal with this issue. Deck mud is comprised mostly of sand - which allows the water to flow through the shower pan to the waterproof pvc liner. As long as the pvc liner has been installed over the required pre-slope, once the water reaches the pvc liner, the slope will direct the water to the drain. In a traditional mortar bed, a clamping drain is used - which has weep holes. These weep holes (unless clogged/blocked) allow the water to be evacuated down the drain pipe.

When using a traditional mortar shower pan - water in/water out system, Mr. Starykov determined that the marble tiles should NOT be sealed. There are several pros over on the John Bridge Tile forum who also believe marble should not be selaed in showers. Impregnating sealers greatly reduce the amount of water absorbed by the marble tiles - but they allow water vapor to pass through the surface of the tile. Once the water vapor has returned to its liquid form, the sealer impedes any surface evaporation. The more water permeable the surface of the tile is, the faster the water inside the tile will evaporate = quicker return of the tile to its natural color.

Mr. Starykov also constructed several model shower pans that used surface bonded waterproof membranes (like your current shower pan that has been constructed using Kerdi). The issue he found with this type of shower pan construction is that the surface waterproof membrane “traps” any water underneath the tile - unlike a traditional mortar bed shower pan as described above. In the event that this type of shower pan is used as the substrate underneath marble tile, Mr. Starykov discovered that the best way to prevent continued marble discloration was by installing the marble tile by using the epoxy method.

The goal of the epoxy method is to prevent as much water as possible from entering and/or getting underneath the tile. In order to accomplish this, an epoxy adhesive + epoxy grout must be used. In his experiment, the only model shower pans constructed using surface bonded waterproof membranes where the marble tile returned to its prior color (with moderate shower use) used the epoxy method + an impregnating sealer.

Based upon all of the research I’ve done re: this issue, I have seen several posts/discussions about shower pans that use a flange drain (the type of drain that was used with the Kerdi system in your shower pan) having a water ring form around the drain - EXACTLY as shown in your photos.

I am getting ready to installl hexagon marble mosaic tiles (a mix of thassos + light gray + charcoal gray marble) on my shower floor. Due to all the posts on Houzz+ the John Bridge Tile forum regarding the above discoloration issues, I reached out directly to Mr. Starykov to discuss his experiments and recommended installation methods. He was extremely helpful - and offered to speak directly with my tile setter. Unfortunately, I already have a surface bonded waterproof membrane installed - so, the best way to install my tile is by using the epoxy method + an impregnating sealer. This isn’t the peferred method based upon the results of Mr. Starykov’s experiments, but I do not want to have my shower pan ripped out in rder to install a traditional mortar shower pan - especially since it already had to be removed once due to a construction issue.

One last comment - someone above mentioned clogged weep holes as a possible issue - however, your flange drain does not have weep holes.

Sorry for the long comment - I hope it makes sense - it’s 3:00 a.m. and I’m very tired (unfortunately, I’m not feeling well and can’t sleep).

Thanks dmac1108! Long comment welcomed, the more information and input, the better.

• "what type of shower pan was used underneath your first marble tile installation where you’ve had no problems? Is it a traditional mortar bed - water in/ water out system?"

it was the same i.e. cement slope with schluter membrane and drain system. I could dig up some photos of that one as well if you think it would help.

• "The goal of the epoxy method is to prevent as much water as possible from entering and/or getting underneath the tile. In order to accomplish this, an epoxy adhesive + epoxy grout must be used. In his experiment, the only model shower pans constructed using surface bonded waterproof membranes where the marble tile returned to its prior color (with moderate shower use) used the epoxy method + an impregnating sealer."

Ok... I think I know what the difference is now. The tiler who did the basement shower used a special grout - Mapei Flexcolor CQ which is a quartz composition and I assume delivers the same performance advantage as epoxy. I looked it up and this is how the manufacturer describes it: "MAPEI Flexcolor CQ is a professional-grade, ready-to-use specialty grout for precision commercial and residential installations with porcelain, ceramic and natural-stone tiles. MAPEI Flexcolor CQ can be used to grout interior/exterior tile, and its dense composition helps to prevent water-based stains by providing water repellency to the grout surface." It is also described as a "Crack-resistant and shrinkage-controlled formulation" so is less likely to develop hairline cracks and related water penetration.

• "Based upon all of the research I’ve done re: this issue, it is common for shower pans that use a flange drain (the type of drain that was used with the Kerdi system in your shower pan), to have a water ring form around the drain - EXACTLY as shown in your photos."

That would make sense as the contractor said it's normal for there to be a small amount of water around the lip of the drain assembly.

So I think the problem is two-fold: a) the tiler used a standard cementitious grout which by its nature allows significant water pass through instead of a specialized grout like epoxy or quartz; and b) the tiler did not pack the grout joints tightly (when I scraped some of them out it was clear that the grout was shallow and there were voids below). I asked a different gc who's a friend and he said it is not unusual for there to be some slumping and gapping after one grout application, particularly on walls, but his tilers would always do a second pass to make sure everything is filled and tight (the basement job was his tiler and indeed there are no visible gaps). I have seen the importance of tightly packed joints mentioned in various other threads/forums (including the John Bridge Tile forum with a massive 26-page thread!)

I think the solution is to ask the tiler to scrape out all of the joints and re-grout with either the Mapei Flexcolor CQ or an epoxy grout. The surface of the marble tile is well sealed with an approriate sealer at this point.

I have another question though: would it be necessary to also scrape out the cementitious wall grout to ensure no transmission on vertical surfaces that would travel down the wall, between the membrane, and lead to water accumulation in the same place, beside the flange?

The problem is you, and apparently the contractor, don't understand shower construction.

You show Kerdi and a Schluter drain in your photos. You and the contractor talk about weep holes and a 2-part drain. The Schluter Kerdi-drain is not a 2-part drain and does not have weep holes.

The Kerdi is the waterproofing. The grout is NOT the waterproofing as you maintain. You harmed the assembly by putting caulk on top of the grout. Mapei Flexcolor CQ is NOT waterproof.

"He said tile assemblies always allow some water down and the waterproofing is designed for that. I disagreed and said the membrane is a more of a secondary structure". He is correct. You are not. Putting sealer on top of the grout will not make it waterproof.

Marble is NOT waterproof. It is very porous and water will absorb into it. Putting sealer on top of it does not make it waterproof, it merely gives you a few more minutes to clean up anything that might stain it. DO NOT put sealer on the bottom of the tiles, as the contractor suggested.

What are your walls made of and how are they waterproofed? There are exposed screws in the wall boards, and the corners are not taped in your photo.

It looks like you have a large "birdbath" around your drain. The area around your drain is most likely lower than the drain, causing the water to collect there. Since marble is so absorbent, it is soaking up the water. Even if the tiles are higher than the drain, the waterproofing surface below might not be. Most likely the waterproofed layer was not sloped correctly, and the tiler attempted to make it correct by building it up with thinset mortar. Regrouting will do nothing to help this problem.

Lastly, I fear that by taking matters into your own hands (sealing, caulking, anything else you did), you have severely limited your ability to hold the contractor accountable for fixing this properly. Once you touch it, you own it.

Thanks for your reply catbuilder.

• "The problem is you, and apparently the contractor, don't understand shower construction."

Well, no, I don't understand shower construction. I wasn't there looking over the tiler's shoulder, didn't record him, didn't tell him how to do his job. It has become my problem to try to understand because after the installation was completed I had moisture discolouration on the tiles and yes, I am quite likely misunderstanding some things. The type of shower (curbless) was agreed upon before any demolition even started. I was never told that I had to choose a type of tile material before the installation started or that the type of shower pan construction depended on tile material - just that any fancy mosaic work was not included in the quote. There are no material specific exclusions in the signed contract. When I said the best replacement tile option was marble, they just said it would have to be sealed and requires maintenance which was fine with me - I have maintained the other marble shower no problem.

I spoke to three people I know personally who used the GC for major renovations and they all said they had no problems, the work was done on time and on budget and any minor issues were corrected quickly without hassle. I chose this contractor over another that was cheaper because I believed in his quality of workmanship and professionalism based on talking to people who hired him previously. I was told by the contractor and some of his other subcontractors that the tiler was super experienced and could do absolutely anything. For example, I wanted to use 24x48 tile for a fireplace surround and I checked first because of the size and was told no problem and his installation work there is beautiful. What else do you expect me to do as a homeowner??

Regarding the drain and what type it is, the contractor did not refer in his own words to a two-part assembly, that is me trying to understand how it was constructed. Someone has already pointed out that it is not a two-piece drain but had a flange. I guess I mistakenly thought all drains in tiled shower floors have a lower and upper part to ensure that water from both above and below the tile will end up flowing down the drain. Maybe they do but that's not a "two-part drain". Sorry if I'm not using the right terminology, that's why I uploaded as many photos as I had.

• "The grout is NOT the waterproofing as you maintain. You harmed the assembly by putting caulk on top of the grout. Mapei Flexcolor CQ is NOT waterproof."

It's not that I believe the grout is waterproof. I didn't say it was waterproof I suggested it could provide a similar "performance advantage" to epoxy (but can be colour matched to existing Mapei grout, thus avoiding different grout colours on the wall and floor). I don't believe it's a matter of black and white, that it is either 100% waterproof or 0% waterproof. My point is that depending on how well the grout is packed and what kind it is, that the grout will allow more or less water to penetrate through it to the membrane, and if so, it would make sense to use a grout that is more water resistant to keep more water on the surface of the tile. Isn't that just logical that water would only soak through tight grout joints but would trickle or even flow through numerous pinholes and cracks and that soaking through takes longer than trickling through and would allow more water to penetrate?

Flexcolor CQ is described as having increased water repellency. The benefits of using it over cementitious grout seem to be supported by the membrane-epoxy installation recommendation made on the website WizeOwl linked to. I know that in my other marble shower where CQ was used I do not have problems but again, I did not supervise that tiler's work either. I am simply hoping that by packing the grout joints tighter AND using a grout material with better repellency that the amount of water penetrating will be small enough to evaporate through the sealer which allows moisture vapour transmission. I am by no means certain that will solve the issue.

• "What are your walls made of and how are they waterproofed? There are exposed screws in the wall boards, and the corners are not taped in your photo."

I don't know exactly but in the shower areas it's a moisture resistant backer board (I think that's what it's called). I wasn't there when the tiler did it so the next phase I saw was after the wall tile was installed. He did the shower floors first so he may have put waterproof membrane on the walls after the photo was taken. This was part of a second storey addition so I could not (nor am I qualified to) manage all the work involved.

• "It looks like you have a large "birdbath" around your drain. The area around your drain is most likely lower than the drain, causing the water to collect there. Since marble is so absorbent, it is soaking up the water. Even if the tiles are higher than the drain, the waterproofing surface below might not be. Most likely the waterproofed layer was not sloped correctly, and the tiler attempted to make it correct by building it up with thinset mortar. Regrouting will do nothing to help this problem."

So if the sloping is indeed incorrect and creating a birdbath, what is the solution? Should the tiler pull up the tiles around the drain and correct the sloping, and if you can't do that with thinset mortar, what material do you fix it with? Pull off all the tile and membrane and start over? Wouldn't it make sense to at least try regrouting with a water repellant material first?

• "Lastly, I fear that by taking matters into your own hands (sealing, caulking, anything else you did), you have severely limited your ability to hold the contractor accountable for fixing this properly. Once you touch it, you own it."

All I did was use matching Keracaulk and add sealer that allows moisture vapour transmission and is made for natural stone. The underlying problem existed before I did anything and I verified that the discolouration would not go away on its own (as the tiler suggested) and I dried it out over 4 weeks to verify it was not permanently discoloured. The only solution the contractor offered was to have the tiler come back to add more grout because of the cracks I pointed out to him and he offered to drop the grout off for me if I preferred to do it myself. I have never grouted and feared I would make a mess whereas with the Kerecaulk I could use a caulking gun and push it into voids as much as possible and easily clean up. For specific, serious family health reasons that I am not going to elaborate on we wanted to minimize anyone coming into the house after we had moved back home. All four family members were stuck at home for work or school and could not leave for the day. I feel I have been more than accommodating and even ended up having to order and drive out to pick up the colour matched caulk. The contractor agreed to that arrangement and paid for the caulking.

I'm not trying to impress anyone with my knowledge of tile or debate best marble installation methods, I'm just trying to get some opinions on how to fix the problem and providing information as best I can. I feel like I'm doing their job here as it is.

Did they use a foam tray or build a mud bed? You need to find out how they waterproofed the walls, and tied the floor waterproofing into the wall waterproofing. It would be very odd to not finish the wall waterproofing before tiling the floor.

Thanks again catbuilder, I appreciate you taking time to respond.

• Did they use a foam tray or build a mud bed?

I am pretty sure it was a mud bed (i.e. cement sloping?) and not a foam tray (you mean a precast tray, right?)

• You need to find out how they waterproofed the walls, and tied the floor waterproofing into the wall waterproofing.

I have asked the contractor to call me and will add that to the list of questions for him to ask the tiler, thanks.

• It would be very odd to not finish the wall waterproofing before tiling the floor.

Compared to any previous tile installations I have had done, this tiler moved very quickly in individual areas. I looked back at my basement shower photos and you are correct, that tiler waterproofed the walls before tiling the floor.

The point being that I suspect they haven't really waterproofed the walls.

In your first photo, the Kerdi around the drain looks like it was done incorrectly, but I can't see it very well.

follow up to catbuilder's question about the walls...

I found an older photo with the label still attached. The walls are DensShield which was used for all shower and tub walls. it is "ceramic tile underlayment" and the installation guide (PDF) for it says "DensShield Tile Backer does not require an additional moisture barrier." I am guessing that is why the walls do not have further waterproofing applied to the surface. The installation guide does not specify that the screws need to be sealed, just that they be of specific materials for specific applications (metal/wood walls, floors, ceilings, etc.).

• "the Kerdi around the drain looks like it was done incorrectly, but I can't see it very well."

This the best I can get, but the next photo I have the tile and drain cover are installed.

The installation instructions clearly state that all penetrations (that includes screws) need to be sealed. It also clearly states that all joints and corners need to be taped with fiberglass mesh tape and prior to that all edges and corners are caulked.

My original plan was for my tile setter to use Mapei FlexColor CQ (Warm grey) for both the shower pan and the walls. After reading about using an epoxy method, I’m not sure what to do. Using an epoxy method makes logical sense to me, however, I am hesitant to do so because of the potential picture framing issues which can occur - the epoxy grout can permanently stain the marble. I’ve asked the pros over at John Bridge about all of this, and no one has really had an opinion on whether I should have my marble set using Mr. Starykov’s method. It is interesting that your first shower pan was installed over kerdi + grouted with Mapei FlexColor CQ - and you’ve not experienced any marble water discoloration.

As you’ve already pointed out, FlexColor CQ’s dense composition helps repel water on its surface. Less water in = less water that needs to evaporate between showers. Another advantage of FlexColor CQ is that you can go back later and address any pinholes/lower grout areas - without removing the exisiting grout. Unlike cementious grout, FlexColor CQ will adhere to itself after the initial install.

I wish that my shower pan had been constructed correctly when first installed. It was supposed to be a traditional mortar shower pan with a clamping drain. However, my contractor was unexpectedly out of town - and one of his employees began constructing the shower pan. I noticed that the pvc liner had been set without a pre-slope. I made comments about it to my SO - and he said he would handle it (I was leaving town for a couple of days). When I came home, the ”final” deck mud had been added and was drying out. My SO and I actually had a little bit of an argument about this - because I knew that it had been constructed incorrectly - and he failed to address my concerns.

There are threads over on JBF that recommend using a surface bonded waterproof membrane underneath marble - so, that’s what we decided to do. The clamping drain was replaced with a kerdi flange drain adapter. I later asked the JBF pros about whether surface bonded membranes are preferred when installing marble, I received mixed answers (although EVERYONE recommended to replace the marble with a porcelain tile).

After replacing everything with Kerdi, I ran across a post by Mr. Starykov on Houzz - which led me to read my first article about his shower pan experiments that I’ve described in my previous post.

All of this gives me a HEADACHE!

I need to address a couple points made by Catbuilder above :

1. Birdbath - it is possible that a “birdbath” has been created by your tile setter which is causing the discoloration issues around your drain. However, as I pointed out in my previous comment, I’ve read posts/viewed photos re: water collecting around the Kerdi flange drain that have been unrelated to birdbaths created by uneven/improper sloping.

I assume that this is part of the reason for using epoxy adhesive + epoxy grout + penetrating sealer - to limit the water absorption.

2. ”Once you touch it, you own it” - I think everyone needs to be extremely careful when offering advice/opinions/thoughts about legal issues. Without having much more information, including the location of the OP’s project, it would be irresponsible for me to form an opinion re: legal liability related to the above issue - and I’ve practiced law for 20+ years. For example, some jurisdictions have enacted statutes that provide a contractor with an opportunity to cure any issues/defects - while other jurisdictions do not. Also, I’m not exactly sure what is meant by the statement, ”you touch it, you own it” with respect to the above issue based upon the details provided by the OP. If the water discoloration around the drain is due to birdbaths, the fact that the OP has tried to replace cracked grout and/or added silicone caulk, does not somehow relieve the contractor for poor/negligent workmanship.

A legal theory that sounds somewhat similar to this statement is one related to intervening causes in tort law. An intervening act occurs after a tortfeasor’s initial act of negligence and results in injury/harm to another, and will generally absolve the tortfeasor of liability ONLY if the event is deemed to be a superseding cause. For example, a person driving an automobile negligently injures a woman as she is lawfully crossing the street. After being treated for a broken arm in the emergency room, the woman has a precription for pain medication filled at a pharmacy. The pharmacist hasn’t slept for the past 24 hours, and mistakenly fills the prescription with a much stronger pain medication at a much higher dosage. The woman later dies from an accidental overdose. The driver of the car is not liable for the woman’s resulting death because the intervening act (the pharmacist filling the precription with the wrong pain medication at the wrong dosage) because it was not a foreseeable event due to the driver’s negligence (hitting the woman while she was legally crossing the street).

Now, if in the above situation, the OP decided to pry some of the tiles loose in order to allow the trapped water to evaporate - and in doing so, penetrated the underlying surface bonded membrane. The OP then continued to let his/her family use the shower, which resulted in tens of thousands of dollars of damage related to wood rot and mold issues, the tile setter would not be liable for these unforeseen damages caused by the OP’s intervening act of penetrating the waterproof membrane + allowing the continued use of the shower.

@catbuilder

Regarding the joints, corners and penetrations being taped sealed and caulked, I just don't know, I wasn't there all the time to know exactly how every stage was completed. The most I can tell from the other bathroom photo is that those tub walls did get a coat of what looks to me like thinset mortar (?) and that it was left to dry before tiling so it's possible the sealing and caulking were done at the same stage.

I would say I already agree that the job was not done perfectly and if the grout was rushed, chances are other steps were too but I'm not sure that helps me identify a solution other than redo the whole thing which is worst case scenario and not a consideration at this point.

@dani_m08

Regarding liability, I really don't think that's an issue here. The contractor and I have had a good relationship so far and agreed on additional charges and credits where appropriate, and he or his subcontractors have resolved all issues to date but in this case I think he is caught between me, who has discoloured tiles due to what I consider improper installation at some as yet undetermined point of the process and the tiler who has done many installations for him and (supposedly) never had a problem. The tiler, when I first pointed out the discolouration said if it didn't go away to get in touch through the contractor and he would fix it. I am trying to get a sense of what a reasonable resolution to request is.

@dmmeurer - I didn’t think that you were overly concerned about liability issues. I just wanted to point out that people need to be careful when making statements/observations about legal issues on Houzz. When people make these types of statements/comments, they have the potential to mislead/misinform the OP and/or other users viewing the discussion thread.

That photo above is not a Kerdi drain, although it appears to be installed on a Kerdi membrane. A properly installed Kerdi drain does not have a "dam" around it.

@catbuilder

• "That photo above is not a Kerdi drain, although it appears to be installed on a Kerdi membrane. A properly installed Kerdi drain does not have a "dam" around it."

Agreed, I assume you are referring to the image @dani_m08 posted? The Schluter shower system installation handbook (PDF) p.25 shows the top of the flange flush with the mortar bed and instructs to use the top of the flange as a screed guide for sloping.

Yes, that's correct. Perhaps your installer did something similar to that "dam" that shouldn't be there? As I said, your installation looks suspect, but it is hard to tell from the photo. It looks like the Kerdi goes down into the stepped area, which it should not do.

@catbuilder I think I understand what you are saying. The Kerdi-Drain installation instructions in the "Connection to waterproofing membranes" section are to:

2. Embed KERDI in the bond coat and work the membrane onto the KERDI-DRAIN bonding flange and mortar bed with the flat side of the trowel to ensure full coverage and remove air pockets. The membrane is carried to the step in the bonding flange (template provided).

And then under the "Grate assembly" section:

2. Fill the step in the bonding flange with Schluter SET®, Schluter ALL-SET®, Schluter FAST-SET®, or unmodified thin-set mortar and back-butter the underside of the grate frame to ensure full support. Press the assembly into the mortar and install the surrounding tiles, ensuring full coverage.
3. Position the grate to match the joint pattern of the tile covering and press flush with the tile surface. Remove all excess setting material.

I am guessing that because the membrane continues into the step, depending on how it was dealt with when tiling and installing the drain grate, it could be impeding water drainage in the inner step area where (if I'm understanding correctly?), since you are only meant to apply thinset mortar and mortar is permeable, it would both expand the drainage area of the physical drain to include the step and also reduce or eliminate the possibility of (drain-related) damming from running the membrane up to the inner part of the grate frame.

Does that sound about right or am I inferring too much? If my description is about right and that is part of the problem, do you think it would be possible to remove the tile around the drain area, use a utility knife and chisel to trim the membrane back, replace the grate frame if necessary, apply thinset mortar to smooth out the drain slope, and then retile?

The photo I posted above is a bonding flange drain that was shown in one of Mr. Starykov’s articles on this subject. When I saw the orange membrane, I assumed it was a Kerdi drain. My post should just refer to bonding flange drains in general. Sorry for the confusion. I am a newbie re: shower pan construction. I‘ve just been doing a lot of research recently in order to avoid having my marble discolor due to water retention.

I have read several discussion threads where specifically Kerdi drains + issue with water pooling around the drain have been discussed. These included comments by well respected professionals who would be able to identify a Kerdi drain. There is always is the possibility (probability??) that the dams around the Kerdi drains were caused by installation error. Anyone who spends even a little bit of time on Houzz looking at bathroom renovations knows all too well how often these shower pans are not built correctly!

I think catbuilder has “nailed it“ in the above post - there may be (i) too much thinset used to set the drain, (ii) a dam that’s been created around the drain (drain wasn’t firmly set into the the thinset?), or (iii) a valley in the deck mud around the drain. Catbuilder clearly has quite a bit of knowledge re: shower construction/proper waterproofing methods.

I do have a question for you - is the marble tile that you’re having an issue with the same as the marble installed previously without issues? There have been a lot of discussions about how the particular quality of the marble tile being installed may have some bearing on the rise in marble discoloration issues. There is a lot of marble being sold in the marketplace that is labeled as ”Carrara” but is actually not from Italy. My understanding is that the density/porosity of marble can vary quite a bit between different varieties. It also can vary somewhat in the same variety. If I hold up two of the Italian Carrara tiles I’ve recently purchased for my shower walls to a light source, certain tiles are much more translucent than others even though they were sourced from the same area. This would contribute to the amount of water being retained inside the actual stone.

Then again, if you have a dam or birdbath around your drain, your marble tile is going to soak up some water regardless of type!

I REALLY want a marble hexagon shower floor - but all of this is making me VERY ANXIOUS. I specifically decided not to purchase the standard Carrara hexagon mosaic tile that I really wanted since white marble tends to have more issues with this - but if my shower pan has any type of water retention issues, I still will wind up with discolored tile.

@catbuilder I meant that from what I understand the membrane is supposed to terminate before the step because a) once the membrance reaches the PVC/ABS drain flange the waterproofing membrane is redundant and b) the step allows water from the surrounding Kerdi'd area (below the tile) to drain into it and if the membrane extends all the way to the inner grate, it impedes the flow that the drain is designed to permit and potentially lead to pooling water.

@dmac1108 it's not Italian marble but neither the supplier nor the tiler expressed any reservations about it. As I said at the top, it was not my plan to use marble for this shower because of the cost and based on my tile supplier's recommendation. They said (and I agree) that there are tons of marble look ceramic tiles out there. Many of them have sufficient variation that you are unlikely to even notice two identical marbling patterns in an installation so the patterning looks very close to a natural material. However, in this case I wanted something with subtle veining and a honed surface that had both a small hex for the shower and a larger hex for the bathroom floor. That reduced options quickly. Some didn't have hex, some didn't have honed and there was too much tile (tub walls, shower walls, half walls, floor, shower floor) for it to be polished (for my taste). The line I chose was from an excellent manufacturer and I've been really happy with all other tile I have purchased from that manufacturer including the 12x24 wall tile installed on the walls (which was not defective). But because it was a new product line, there were quality issues with the large and small hex tiles. I had to find a replacement quickly and this was the best option.

I personally would recommend that you have a really good look at non-stone options because they are really nice. Go to the showrooms and look at the samples and the catalogues and photos of installation to see how much variation there is. I don't think my problem is the marble I think it's the installation but obviously if I didn't have porous stone I wouldn't have the discolouration issue. Whether or not a birdbath or dam is a problem in and of itself in the absence of discolouration is a different question I will leave for the tile experts. Personally it only makes sense to me that any tile installation should allow water to flow as freely as possible above and below the tile and maximize the water that flows across the surface of the tile and down the drain without penetrating below.

I am still waiting to hear back from the contractor but will post any relevant updates on resolution.

@dmmeurer was this ever resolved? I have the same exact issue. Darkness only around the drain area and takes weeks to dry and return to normal color after each shower. Thanks

There is a lot of BAD information on HOUZZ threads. This thread being classic case full of bad info. Do not get your homework done on this thread plz! you start a new thread youll have at least a chance at some good information!

Okay, I scanned through the discussion - admittedly didn't read everything completely:

Here's the thing:

1.) Marble is porous. Grout is porous. Six sided sealing and epoxy thinset on the floor can reduce the chance of it showing - but it's still possible. That's true no matter what.

2.) The water barrier is not the tile or grout, it's the membrane under the tile and grout. That means that it's designed for water that gets past the tile/grout (see #1) to migrate towards the drain and eventually find its way to weep holes in the drain. This water is not free flowing. It's migrating around/through tiles and thinset under the tile. It hangs around for a while.

Hopefully the slope towards the drain is done properly, and the details on the drain are done properly so that the water does eventually clear. Details matter a lot here.

3. Even if the drain and slope are done properly, marble sitting on a wet surface is very likely to absorb water from beneath and discolor. And the sealant on top slows the evaporative drying, prolonging the discoloration until it completely clears to the drain.

4. In conclusion: Don't use a porous stone on a shower floor - no matter how well constructed the base is - if you are going to be picky about discoloration from water below. Use glazed ceramic tile - or better yet - use a cast iron base and you avoid a lot of potential leaks and other issues.