Limestone Discolouration

Fraser Tiling · Feb 25, 2016

Hello guys,
just fixed 20 metres of 15mm 900x600 tumbled limestone to a screeded floor with underfloor heating using Ultra extended set white flexible adhesive.
When I returned to seal the tiles there was a noticible discolouring to the tiles which I put down to the moisture still coming through the stone.
They were laid three weeks ago and the underfloor heating was turned on a week ago but the tiles still dont seem to be drying to a uniform colour.
I have laid similiar tiles before with the same adhesive and havent had this problem.
Instarmac have seen photos of the tiles and say the floor needs more time to dry and eventually the floor will dry, but Im worried about the tiles being stained by the moisture.
Anyone have any experience with this problem or any advise?

Tile Shop · Feb 25, 2016

What type of screed is it and how thick?
How long before tiling was the screed laid?
How wide are those grout joints? (from the images they look to small for limestone with UFH and no uncoupling)

Fraser Tiling · Feb 25, 2016

standard sharp sand cement screed, laid on 12 of december so plenty of time to dry, only a 2-3mm joint but not had problems before with a tight joint on antique edged tile

One Day · Feb 25, 2016

Extended set adhesive with white limestone. I think the word "extended" is the problem.

Fraser Tiling · Feb 25, 2016

impish said:
Extended set adhesive with white limestone. I think the word "extended" is the problem.

agreed, wont be using extended set adhesive again with stone, although states on the bag its suitable for natural stone, manufacturers claim it will dry eventually but im concerned it may stain or discolour the tiles

Ian · Feb 25, 2016

Was the stone back skimmed or just adhesive troweled onto the floor?

Tile seller · Feb 25, 2016

I can only think that this is due to using the Extended open time adhesive.
I received a technical bulletin only a few weeks ago regarding using only fast set with natural stone, although never had much of a problem before.
If you've not sealed it yet then best to wait and hope it does dry out first.
People complain about porcelain being hard but, you don't get these sorts of issues with it.

Just Rizzle · Feb 25, 2016

Fraser Tiling said:
standard sharp sand cement screed, laid on 12 of december so plenty of time to dry, only a 2-3mm joint but not had problems before with a tight joint on antique edged tile

what makes u sure it had plenty of time to dry did u moisture test it.
my take on the photosis moisture rising up through the floor.
can you take a small cut one up and test the floor. you might find moisture trapped under the tile
you can see your trowl marks through them was it a 12mm trowel

Fraser Tiling · Feb 25, 2016

no, I didnt skim the back of the tile, used a 12mm notched trowel on a shallow bed, some of the tiles were back buttered to adjust heights, hence in places you can see trowel marks coming through, once again although not text book, have been laying stone for twenty years and never seen anything like this before.
The screed looked a uniform colour, and didnt appear to be damp although the floor was very cold, i also tiled a raised metal "manhole" cover, although very deep bed, it also is discoloured.
I havent sealed the floor for obvious reasons.
My main concerns are whether the tiles are going to stain, trowel marks, will eventually disappear, and I think the extended setting adhesive is clearly the main culprit, perhaps a wider joint may of helped the drying process, and cold temperatures wouldnt of helped either.
Im reluctant to use any cleaning products such as Power Clean or add any more moisture to the floor as suggested by some local tilers.
The UFH has been on for 6 days now, and is upto 21 degrees, and as expected there been little to no change in colour, hopefully this is a good sign that the moisture is being forced up and out of the stone, and within a short time the tiles will dry.

Chalker · Feb 25, 2016

The underfloor should have been commisioned before tiling. I'm pretty sure this is the moisture from the screed trying to get out.

One Day · Feb 25, 2016

Back home now and had a closer look. I didn't pick up on the uncommisioned ufh part.
I'd say that it's primarily the additional moisture of the extended set not yet gone, and in part - moisture rising from the screed still.
Good sign is the dryness around the grout joints. I think this will dry out but could take quite some time yet...

For future - please use Ditra and a rapidset. That would mean you could fix safely onto uncommissioned heated screed and no risk of residual moisture lurking in the adhesive.

White Room · Feb 25, 2016

Was there no decloupling mat fitted ?

Fraser Tiling · Feb 25, 2016

Chalker said:
The underfloor should have been commisioned before tiling. I'm pretty sure this is the moisture from the screed trying to get out.

Thanks Chalker, that makes alot of sense, will check with the builder that the UFH was tested before hand, I must admit I cant remember whether I asked, to be fair with their experience they should know.
Do you think there would be any staining if the screed is the issue?

Fraser Tiling · Feb 25, 2016

whitebeam said:
Was there no decloupling mat fitted ?

no, wasn't deemed necessary by the builder, dont think there would be an issue if it was used

Fraser Tiling · Feb 25, 2016

impish said:
Back home now and had a closer look. I didn't pick up on the uncommisioned ufh part.
I'd say that it's primarily the additional moisture of the extended set not yet gone, and in part - moisture rising from the screed still.
Good sign is the dryness around the grout joints. I think this will dry out but could take quite some time yet...

For future - please use Ditra and a rapidset. That would mean you could fix safely onto uncommissioned heated screed and no risk of residual moisture lurking in the adhesive.

agreed, I would never spec a floor and not use a decoupler

J Sid · Feb 25, 2016

Fraser Tiling said:
no, wasn't deemed necessary by the builder, dont think there would be an issue if it was used

Deemed not necessary by builder, his trying to save money and when it all cracks he will blame the tiler as the tiler is the expert and should know what to do.
If its coming from screed it could take many weeks to dry out now. Tell the builder, due to his insistence to not use a uncoupling membrane he must now wait until floor is completely dry be you can seal it. He must also keep everyone off it or it will get stained.

Fraser Tiling · Feb 25, 2016

Thanks to everyone that's posted on my thread, confident we have found the cause of the problem.
This forum is a brilliant tool for just these kinds of issues, cant thank you guys enough.

Fraser Tiling · Feb 25, 2016

JulianSidney said:
Deemed not necessary by builder, his trying to save money and when it all cracks he will blame the tiler as the tiler is the expert and should know what to do.
If its coming from screed it could take many weeks to dry out now. Tell the builder, due to his insistence to not use a uncoupling membrane he must now wait until floor is completely dry be you can seal it. He must also keep everyone off it or it will get stained.

agreed, often builders offer the customer the option, and depending on budget the customers have the final say.
Unsure of the details on this particular job, but you're right, ultimately it has fallen on my shoulders when shortcuts are taken.

Just Rizzle · Feb 25, 2016

dosnt matter how long you've been tiling you learn some thing new every day

Fraser Tiling · Feb 25, 2016

RayTheTiler said:
dosnt matter how long you've been tiling you learn some thing new every day

perhaps not every day, but yeah this game keeps you on your toes and bites you when you become complacent.
Just cant take anything for granted.

Martyn Leeds · Feb 26, 2016

Ultra Rapid is the slowest rapid I've used recently. That gives plenty of time, so no need for Standard Ultra at all in future..

J Sid · Feb 26, 2016

The builder didn't cover the floor up after you laid it so other trades could work over it by any chance?

Fraser Tiling · Feb 26, 2016

JulianSidney said:
The builder didn't cover the floor up after you laid it so other trades could work over it by any chance?

dont know, it hasn't been mentioned, the grout and sealant were supplied by the tile suppliers, and there were two bags of extended set adhesive put with the supplied materials.
I thought the adhesive was sent by the tile suppliers, as the recommended adhesive, and i bought more of the same to complete the tiling, it was only after the tiles were fixed and the problem occurred that the customers said that the adhesive wasn't supplied, and was left over from a previous tiling job.
Had I known this, I would have used rapid set.
I have since spoken to the tile supplier and asked what adhesive they recommend for fixing, and they didnt specify a rapid set, they also had a very bad attitude and offered no help at all.
Ive got Ultra coming out to see the floor this week, so will see what they say.

Bill · Feb 26, 2016

poor quality stone too will not help.

Just Rizzle · Feb 26, 2016

you need to take a tile up then youll get your answer my bet is like I said wet screed no way would it be dry enough in the winter months to lay stone. looks like the screed is sweeting buckets my fear for you is that it may cause the whole floor to fail.

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