Underfloor heating - Tile marks - Help!

[kohini]

Hi all

I am a newbie..

Last summer we had wet underfloor heating installed in our extension. In the last couple of months I have noticed grey marks appearing on the cream porcelain tiles where the underfloor heating is. They are a series of parallel lines (straight and curved lines)

This was covered with concrete and a layer of porcelain tiles. The tiler at the time assured that the correct adhesive was used.

Does anyone know what could cause this or has seen this before? I am guessing it is the heating of the adhesive, and the patterned parrellel line could be the way the adhesive was applied with the semaring tool?? Will this get any worse?

I have attached a couple of photos, one of the tile marks (should see some faint horizontal lines) and another of the underfloor heating pipe layout prior to concrete)

Any advice greatly appreciated

[Dave]

Have you got a pic of the tiles from further back...?

[whitebeam]

What colour adhesive was used

[Dan]

How long has it been down? There still could be moisture in the floor.

The temperature should be far to low to cause colour changes as the temperature changes. I'm pretty sure your porcelain floor would need thousands of degrees before that turned a different colour.

Does the colour turn back when it's off?
How long has it been down?
If you leave it on do the 'lines' appear to get bigger? (Suggesting it might be moisture coming out of the floor perhaps?)

[Fred]

Thats really odd I reckon. Could it be that the type of tile used conducts the heat in such a way it shows though it?

[kohini]

Thansk for the speedy reply!

Just attached another photo from further back...

I will have to do further testing with the heating on/off and feedback to you. The floor has been down since July 2008.

Don't know about the moisture under the floor, the rood of the extension was built before the heating was laid and tiled so don't think it was laid whilst wet.

[kohini]

PS - sorry dont know what colour adhesive was used

[Dave]

As i thought .......that is adhesive shadowing through the tiles....insufficent coverage on the back of the tiles and thats why you can see the ribbed effect you have....

If the tiles had been back skimmed and a better coverage on the floor then that would not show....looks like grey adhesive as well as the marks have bled into the tiles...

Needs to be a re-call to the tiler..

[whitebeam]

That was my thought on this one but never actually heard of it on porcelain

[kohini]

So do you mean the tiler was supposed to put adhesive on the back of the tiles as well as the floor? Does this mean that when the adhesive runs, it will run evenly?

What colour should the adhesive be? Will other colours not run?

I take it we would need to get the same tiles (and batch) which is going to be difficult.

Thanks again for the advice

[whitebeam]

Some tile have a deep profile on the back and need filling because you don't get a good bed between tile and floor. If the grout is a light colour I use a white adhesive but have not heard of a grey adhesive grinning through a porcelain tile before

[Dave]

You lines you see are just the adhesive ribs from his trowel...

These ribs should be deep enough to collapse and form a 100% coverage on the back of the tile along with a back skim it will prevent the shadowing you have there...

Basicly , all it is , is an incorrect fixing method was used....

[beanz]

Scary. Would the ribs have been noticeable if the tiler had used white addy? Or should he have checked his tiles to make sure he was getting full coverage maybe? I just want to make sure i don't end up footing the bill for this sort of ****up in the future!

[whitebeam]

If he had back skimmed the profiles on the back of the tile, probably not albeit white or grey adhesive

[Dan]

As i thought .......that is adhesive shadowing through the tiles....insufficent coverage on the back of the tiles and thats why you can see the ribbed effect you have....

If the tiles had been back skimmed and a better coverage on the floor then that would not show....looks like grey adhesive as well as the marks have bled into the tiles...

Needs to be a re-call to the tiler..

Spot on there mate. That's pretty clear in that picture.

[Dave]

Scary. Would the ribs have been noticeable if the tiler had used white addy? Or should he have checked his tiles to make sure he was getting full coverage maybe? I just want to make sure i don't end up footing the bill for this sort of ****up in the future!

White or grey, it's the moisture that has bled and stained....if you back skim then the colour change is fully uniform....

[beanz]

White or grey, it's the moisture that has bled and stained....if you back skim then the colour change is fully uniform....

Would you recommend back skimming on ALL light tiles though, or are there particular circumstances that this is likely to happen?

[Dave]

I back skim all floor tiling and the majority of wall tiling as :

1: it prevents shadowing on light bodied tiles etc

2: it creates a very good bond with the tile bed.


This is just my technique and works extremely well....Also if your tiles have profiled backs it deffo gives a better bond..

Back skimming is not to be confused with back buttering...

Back skiming is using the flat side of the trowel and put adhesive onto the back of the tile and scrape it back off again leaving a very fine skim on the back and back buttering is applying adhesive either with the notched side of the trowel or using a margin trowel and spreading the back for build up etc....

[Dan]

I back skim all floor tiling and the majority of wall tiling as :

1: it prevents shadowing on light bodied tiles etc

2: it creates a very good bond with the tile bed.


This is just my technique and works extremely well....Also if your tiles have profiled backs it deffo gives a better bond..

Back skimming is not to be confused with back buttering...

Back skiming is using the flat side of the trowel and put adhesive onto the back of the tile and scrape it back off again leaving a very fine skim on the back and back buttering is applying adhesive either with the notched side of the trowel or using a margin trowel and spreading the back for build up etc....

Notice poo-hot advice when you see it people!

[kohini]

Hi all,

Still trying to sort this out. Found some left over adhesive and it is called 'Bond It Rapid Flex - Grey part flexible floor tile adhesive' Not sure if this was used in the underfloor heating part of the job.

Is this the correct adhesive? Although it seems like from the recent comments it's just to do with the amount of adhesive irrespective of colour...
One question, if sufficient adhesive was used, will it bleed evenly, making the whole tile darker (instead of ribbed). And will the bleeding only occur on underfloor heating only?

Thanks for your support...

[Dave]

It's just the tiles that have soaked up and shown the ribs....as you say if 100% coverage on the tiles was achieved then yes you get even colouring of the tile...

When tiles are suspect like those , i backblade adhesive on the tile to make sure of even shadowing.....

[kohini]

Hi Dave, many thanks for your advice.

I am still trying to get my head round this....How would you apply the tiling in my situation?

I have underfloor heating in half the room. The entire room is tiled. If the tile bleeding only occurs in the half of the room (the part with underfloor heating) and we apply sufficent adhesive, then we would get half a room darker (albiet evenly) than the other. Am I right in my assumption?

How would you apply in each half of the room? Type/colour adhesive and application method in each half to ensure even colout throughout?

Thanks again

[Dave]

AHHH.. i didn't see you say about only half the floor had ribbed marks....

2 ticks i will read back through the thread..

[Dave]

I have just looked at the pic again and that is deffo adhesive ribbing....But for it to happen only in the ufh bit is very strange....it's as if the ufh could have caused the adhesive to reacte.....I think a call to the adhesive manufactuer is needed to see if it is suitable for the job in hand then take it from there....

I also think it might be wise to pop a tile up and see exactly wot is going on under the tile...

You will not damage the ufh as it is within the screed as long as you do not over impact the floor when trying to get a tile up...

It has got to be the ufh causing the adhesive ribs to show but why...first on me this one..?

[basshunter]

Kohini,
Where did you buy your tiles from?do you know the make? and how much did they cost?

[Dan]

Like the tiles then basshunter? You thinking for your own home? Or is this to help with the situation somehow? .... Or thinking about it a bit more, perhaps you want to avoid using them now?

[kohini]

Bought the tiles from Tile Giant. They are 'Kenora Polished Porcelain'.... something like £12 per sq metre.

I suppose if I get them replaced I don't want the same discolouring occurring, even though it may be even discolouring

[bootsmckiber]

Definatly used the wrong addy,I always use white addy when using light tiles for the extra few dollars for a 50lb bag(which the customer pays for anyways)always flat trowel the back,that usually stops anything that might cause discolorment from soaking into the tile.Good luck on that one,it ****es me off when people call themselves tilers and go in and do somthing you could find in a tiling for dummies book,it makes legitimate tilers look bad,I truly hope you have the time and money to take the hack to court,especially on heat,costs a few bucks(quid).
Mike

[basshunter]

"Different manufacturers work to different standards to meet varying market conditions and requirements.The blueprint is not always adhered to as strictly in quality control and selection of 1st choice materials as in the past..."Porcelain" no longer guarantees a product that complies with the original standards.Therefore,installation methods,care and maintenance considerations,and performance expectations vary."

You may be pleased to know a quick google showed this:

KENORA POLISHED PORCELAIN 40X40CM BARGAIN £6.00m2 on eBay, also, Tiles, Bathroom, Home Garden (end time 26-Apr-09 13:02:41 BST)