That's the mortar bleeding through. Called Spot Fixing or Spot Bonding. (basically applying the mortar adhesive in 'blobs' instead of buttering the entire back of the tile. )

What was used on the back/underside? what product?

Do you know what mortar or adhesive he used? please tell me he didn't use Mastic???

(If he used mortar, I hope he didn't use the Gray color. A White mortar meant for marble and natural stone should have been used)

this picture shows the same issue as yours.

Natural stone floor installed using spot fixing. This has caused discolouration of the tiles.

What causes the discolouration?

Tile installation requires the use of moisture with in the adhesive used to fix the tile. When using spot fixing to install tiled surfaces this moisture can collect in the voids between the tile, adhesive and sub floor. When this occurs, minerals from the adhesive or concrete sub floor become activated. These minerals can then travel through to the face of the stone leaving a ring mark or staining effect. Each ring outlines where the spot of adhesive is under the stone.

you can see how he 'blobbed' it on the back.

It's called "spot bonding" (which isn't how it's supposed to be done.

Any good tiler knows these should have been 'buttered' on the back like you would butter toast, spreading the thinset all over the back, and then troweling the mortar onto the floor as well.
examples:

correct way,,,^ troweling the back, and trowling the floor. (and it has to be WHITE, not GRAY)

You're not going to like the advice.

It needs to be ripped out and redone. And the tile installer needs to pay for everything. It's completely, 100%, his fault.

I'm sure you paid them in full already, so it might be hard to get them to fix it. It is on THEM. I would call the owner of the company (or the tile guy if it's just him) tomorrow and tell him what's happening. If after 4 weeks it hasn't evaporated (especially in the summer!) It's not going to.

don't let him say, "it will be fine. give it more time". you'll never hear from him again.

I'd call in a stone restoration expert and show them the products used and see if he can rectify it. (although, it's highly unlikely.)

And Of course Her tile installer should be the one paying for it, as this was his fault.

Any pro tile expert knows how to lay large format tiles. He screwed up and it's on him to get it fixed.

That's a shame. Those are gorgeous tiles and a very beautiful looking floor. I can't imagine why he wouldn't have used the trowel to mortar the entire floor surface. with those heavy tiles, it's just Tiling 101.

The other issue you'd have (or your friend) is the parts of the tile that didn't get the adhesive on the back will leave a hollow sound and be more likely to crack or break (since they aren't supported w/the mortar). If you 'knock' on the parts of the tile w/o the blobs, it will sound hollow.

Removing spot fixing discolouration

Removing staining associated with spot fixing is very difficult. This is because it is not just on or near the surface, but right through the stone. Scrubbing the surface with a residual grout or efflorescence remover such as LTP Grout Stain Remover may help to lighten the appearance of the ring marks, but it does not always completely eliminate them. It is also often harder to remove the marks if the surface is sealed when laid.

Acid based cleaners such as LTP Grout Stain Remover can also affect acid sensitive surfaces such as limestone or marble, however if the they are rough cut or tumbled the contact with an acid makes little difference to the overall appearance provided that it is applied evenly. Stones such as sandstone and slate are not normally affected.

Quite often the only effective method of resolving this issue is to rip up and replace and then complete tile installation correctly following your adhesive suppliers recommendations.

same issue like yours:

https://www.tilersforums.com/threads/dark-patches-appearing-on-limestone-floor-tiles-after-laying-and-sealing.48860/

**** there is a slim chance that applying a penetrating enhancing sealer may darken the rest of the tile to match, but I wouldn't bet on it. and you'd have to try it in a inconspicuous spot to see if it would work***

Thanks Beth.

We did in fact clean the stone using a "sander" with water and it does get the stain off but then the water floods under the tile where the empty cavities are below and it seams back through and causes the marks again. I definitely think this is not possible to fix but my contractor is still sure he can fix it I am just curious to hear people option of a) his work b) what went wrong c) if there is any hope for it.

The lightened square above is where you see the water and refinishing sander did partially work but the stains remain along the edges. tHIS ALSO CHANGES THE COLOR AND TEXTURE OF THE STONE.

Sadly Beth already answered your question. A attractive. B spot application of adhesive C tear out and redo

No easy solutions here. You didn’t answer what mortar was used, do you know? Do you have any photos during install?

It’s definitely a limestone, it’s just an English limestone. we have many photos of it installed perfectly with no issues over there and is a really common color stone over there.

This is a photo she sent me of mid laying.

I have sent her this thread and while I think she already knew the reality of tearing it out i thank you guys in helping her probably putting her foot down in him trying to fix the issue.

Unfortunately she actually didn’t hire by price and tried to pay for skill. Unfortunately the guy who she hired had others do the work and frankly didn’t care. She has only paid half but for obvious reason stopped them working and moving forward with any grout.

Yah...that photo says it all. Is that OSB I'm seeing? With seams still showing?

The mortar/thinset that they used did NOT make it past the edge of the stone. No trowel marks. Nothing to indicate this was done with any sort of knowledge.

If that is OSB, did anyone check the floor deflection rating?

It’s Kerdi. Which is a shame to have ruined. There’s a lot of right things in that photo, but there appears to be wrong too. Like that mastic bucket. That’s already an automatic redo, just based on that.

That’s still not a definitive diagnosis of the beginning of where it all went wrong. Thsts the tile setter chosen. That’s the source. The spots are without a doubt a clue Of cluelessness. Get in a certified tile flooring inspector, and pull up a couple to see and write a report. Blobs are death. Mastic is death. That might get you money back. It might not.

Or just hire better for the redo.

It’s Schleuder-Kerdi, a waterproof antifracture membrane. The mortar was covered by it so the staining isn’t caused by the mortar bed but likely by the moisture from the thinset. Everything I’m reading says they should have presealed the limestone. Has anyone done that before or know anything about presealing limestone before setting it?

FYI- Catherine above is my friend with the issue following up

Anyone also know anything about the difference between using Ardex 5 vs a rapid drying thinset, like Ardex N23, to help prevent moisture issues like this by having the thinset dry more quickly?

Sealing only prevents grout from staining. Sealing doesn’t waterproof, or prevent etching, or any of he other issues with limestone. Sealer doesn’t fix LHT tile spot set with mastic from having the oils in mastic staining telegraphing through issues.

Is Ardex 5 mastic?

X5 is a medium bed mortar, rated for this type install *when done correctly.

Again the issue is spot bonding. There is no fix but a full tear out. This does not meet industry standards.

sealer etc not the answer.

the problem is the spot bonding and the type of adhesive they used. I've explained why in my first comment.

Presealing the limestone would only make it easier to clean off any mortar residue from the surface. pre sealing does nothing underneath the tile w/the mistakes of spot bonding.

You never answered the question. What did they use to set the tiles???

I see something in a bucket back here and it doesn't look like Versabond. If they used a Mastic product, it's even worse. If they used a pre-mixed Mastic for this natural stone, it's a complete NO! I can't stress that enough. And the fact that they spot bonded it, well, It obvious what happened.

They do make a mastic for natural stone, but I can't tell if that bucket is the one.

In either case, I would never have used this product for limestone. no way

you can't use those heavy acidic products on limestone without affecting the overall look of the stone. (as your friend has already discovered)

This is a beautiful room. I can see why she picked this stone. its stunning.

Is this over in England? they don't use heated floors for an application like this? (prob good that they didn't because during the tear out that would have to go too)

I've shown the product that should be used, and the way to apply it. If your contractor won't fess up to his error in hiring the wrong people, I don't know what to tell him.

have him call in a stone restoration expert, but I'm sure they will say the same thing. you can't undo the spot bonding or the use of Mastic.

Cathrine:

***there is a asterisk after 'most natural stone'. So I don't know if this is suitable for limestone.

ARDEX X 5™ is a highly versatile, polymer-modified, large format and heavy tile and stone mortar for setting porcelain, quarry, ceramic and most natural stone* tile over common interior surfaces, including exterior-grade plywood, as well as exterior concrete and masonry surfaces.

Key Features

• Ideal for large format and heavy tile and stone applications up to 3/4″ sq. notch trowel
• Use for setting porcelain, quarry, ceramic and most natural stone tile
• Excellent sag resistance
• Very creamy, easy to apply
• 3-hour pot life
• Interior and exterior use; water and frost resistant

ARDEX N 23 is a rapid-setting, thin-to-medium-bed mortar that is ideal for interior installations of moisture-sensitive natural stone, marble, granite, porcelain, quarry and ceramic on horizontal or vertical surfaces. Recommended for all tile sizes, including mosaics, ARDEX N 23 is suitable for use over concrete floors with in-floor heating systems. ARDEX N 23 has proprietary ARDEX self-drying technology to prevent staining, discoloration, warping and efflorescence. Easy to mix and apply with excellent bond strength and sag resistance, ARDEX N 23 has an open time of up to 30 minutes and a 60-minute pot life.

Key Features

• Use for setting porcelain, quarry and ceramic tile, ungauged stone, translucent marble, glass and natural stone tile
• Fast setting – grout in two hours
• Ideal for moisture-sensitive natural stone tile
• Self-drying technology – will not contribute to staining, warping or efflorescence
• Outstanding coverage – 103 sq. ft. (9.5 sq. m) per bag with 1/4″ sq. notch trowel
• Thin- to medium-bed installation up to 5/8″ (15 mm)
• 1-hour pot life
• Use for interior floors and walls
• Extended open time of 30 minutes
• Excellent bond strength and sag resistance

Which product was used??? I wish someone would answer this question.

with something like limestone, a low alkaline Mortar is recommended to decrease any staining problems.

I would talk to the people over at Ardex and ask them which of their products is a better choice for your stone.

Also, Kerdi is not proper for this application. Ditra, perhaps but NOT Kerdi. Fine for shower walls and floors but in this instance, it waterproofs the floor and any mastic or residual moisture will travel upwards and go into the limestone. Yeah, it might eventually dry out, but with spot bonding, it'll take forever and you STILL don't have any support around the corners. Sad to say, but it's a total tear-out.

Hey Beth, thanks for all your help. They used Ardex 5 thin set to set the tile.

Unfortunately, we do have radiant heating under these floors, which is also going to be total redo after ripping the tile up. I’m so heartbroken. This process has been horribly painful and yet the tiler is still trying to “resurface” as a solution. He’s proposing spending next week having a guy in here pouring water on it to clean and then hone with a 150 machine, which sadly changes the color and texture of the tile slightly and while it does actually pull up the stain circle marks, it then leaves other new marks where the water form the cleaning sleeps into the grout lines and moves back into the tile. Once that cleaning water dried, it left new stains.

Sorry. Re-surfacing isn't going to do what you want.....

they used Ardex 5? did you see where the asterisk is next to the "Certain Stones" ?? Why don't you call ARdex and speak to a rep? See what they say. Although, at this point it's moot since it's obviously the wrong adhesive.

What's wrong w/getting the Portland based mortar in the bag and mixing it? They couldn't be bothered? (and the bags are cheaper than the pre-mixed ARdex stuff)

you shouldn't have to have your beautiful tiles resurfaced or have to 'settle' with new marks.

limestone is going to be damaged by the acid process. It's going to change the way the stone looks. Is that what you want?? I hope not.

That's absolutely ridiculous. I'd demand a complete do over, the proper way. Any tile expert knows the dangers of spot bonding. and any tile expert worth his salt knows that limestone is one of the most porous materials for tiles. he should know how the products he use, and the way he uses them, work together. If he doesn't, then he shouldn't be working on a costly install such as yours. but that is on your GC or the Tile company boss.

In any case, You are paying for skill and time. I can't imagine what this is costing you. In no world should any one have to come in and resurface your stone so that it will HIDE their mistakes.

nope. You tell them you want a complete do over on their dime. start taking lots of pictures.

in fact, go over to John Bridge tile forum and post these pics and everything over there. Those guys are the best of the best and they'll tell you flat out how to get it done correctly.

https://www.johnbridge.com/vbulletin/forumdisplay.php?f=1

Amazing. Thank you, Beth!

Actually, reading all these comments, I think you would be best served getting a "qualified tile professional" over for consult rather than relying on virtual advice on the internet. Regardless of materials used, it can't be saved now and it's time to plan the re-do with a PRO. No matter the materials, you got the old five of diamond spot method and you are seeing the results And this is only the beginning of the problems as more will come later.. If you don't know how to find a Pro in your area, send me a PM and we'll find you one. You can spend a lot of time personally trying to understand what a seasoned professional knows (and it's OK to research), but you will get where you need to go faster with professional advice onsite. It is a sad situation and we as industry professionals are always disappointed when the consumer experiences the result of an unprofessional job. Remember folks, there are different levels of skill required when hiring someone to do a "tile job". A friend might tell you that they know someone who did a great job installing ceramic tile in their laundry room, or on their backsplash. No guarantee they are skilled working with natural stone, and over heat, and I could go on. Just like tiling a shower is a very different skill level than tiling a bath floor. Your floor should look more like this limestone floor installation below (although different limestone). So sorry you are dealing with this.

dragon, I think she may be in England?

Catherine, you in the states or in Britain?

she is in Usa California. tile is from uk

Before I tore all that out, I'd take a roofing torch to it. I've used heat to drive spots out of stone nearly instantly.

I can't see sanding the limestone doing any more than hemorrhaging money and time. He needs to suck it up, tear it up, and replace it properly installed.

maher,,,thanks. Heated floors in Calif? lol I'm here and can't even imagine when I'd turn them on.

Thanks everyone for all the help everyone. Just so everyone knows with washing them over and over with water they eventually dried out over a few months. Just thought everyone should know

I just had installed on a fireplace and it is very splotchy and darker than I want. How long and what did you do to get it to dry?

*Limestone

It has now completely dried. Washing with water daily helped the process . Just took patience but happened in the end :)

Probably took 3 months in total

But technically it’s an installer mistake as you should seal the stone before . Our installer pretty much refunded us completely

Thank you for your response!!
I am debating about throwing in the towel for the limestone and starting new Or waiting for it to dry and need to decide this week.
I hope it’s okay to ask some questions:
-I thought it was not good to get limestone wet, I was under the impression that it furthers the staining/darkness. Why did you wash it daily? And how did you do this?
-Is there anything you did to expedite the drying?
-When it finally became dry, did it go back to its pre installed color with zero stains?
-What type of sealer is recommended?
-When was it grouted?
Our stone has not been sealed nor grouted yet. When I saw how it looked, I asked the tiler to pause the job.

If I had known about the staining and change in color, I would have chosen a different tile.
This has been very frustrating and disappointing and time consuming.

Thank you again for your time!!!!

Wendy, your limestone is over a fireplace. Why don't you accelerate things and burn a fire to see if the limestone above the opening starts to dry. You could have an answer quickly.

Thanks Paul. We did burn a fire last night. Unfortunately minimal change. The tile store said it “should” dry out. We live in CA where it has been raining a lot. We have a dehumidifier and fans going constantly. At this point, it seems that it could be months, if it dries at all. Would sealing prior to install make that much of a difference??

White thinset

We used water because we were trying everything and it was the patches we wanted to even out first. It was either try everything or tear it all out. Not sure fans or dehumidifiers did much. Honestly I’m not a professional so not sure what was working. Probably the chemicals being washed out as they came to the surface . Limestone can definitely be washed for sure but we didn’t use any soap etc. yes the tiles ended up looking good as new apart from where some idiot put tape down for some reason. But you would never know now the panic and disappointment we went through. Definitely have to seal limestone or any plutons tile before hand is what we learnt at least in our case. Our limestone was from the UK not sure if that makes a difference. Here were some photos first day and two months after. Now it’s even better that this even . Our installer claimed on his insurance I believe because pretty much everyone said it wouldn’t go away, and that was after having several stone people over to see what they would advise. We thought it would never go. But it did.

I wouldn’t let your contractor off the hook. But also I wouldn’t go straight to thinking it will never be fixed. Because of you look at this thread most people said would need to be torn out but that would have been a nightmare

Hi - I'm hoping you may be able to elaborate on the washing with water approach.

I have 250 square feet of large format limestone tiles installed - two and only two of them have weird dark blotches - nothing matching trowel marks.

All installed on level surface with white mortar, all fully back buttered with flat trowel. Two of the tiles were not happy with this approach it seems, and since I only have two, I think it would be simple to do the washing with water method you mentioned. Is it as simple as spraying/wiping daily with water?

Thank you!

Similar problem - limestone installed on radiant floor. The sample was not splotchy at all - Its been two weeks since install. What is the issue and Will this dry out or remain blotchy?

Even if it eventually "dried out", the problem of the lack of support for the tile remains. Spot bonding makes the installation very weak, and prone to breaking.

@Minardi I do not see any evidence or the appearance of spot binding in that picture. Where do you see a lack of support fort he tile as well? Always looking to learn and I never like to assume.

Hi Maher,
Did you scrub with water everyday or just mop over? Have same issue at mine currently

Hi Maher,

Here is my floor 10 days after install. your floor gives me hope. Can you please share how you washed the floors and how often you did it ? Did you just wipe with water and towels or sponges? Did you dry after or allow water to absorb a bit? Would love to know your secret. Thanks so much!

I would also LOVE to learn how others floors turned out after time.

Thanks so much!

Natalie