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

 

[DHTiling]

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

 

[White Room]

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

 

[DHTiling]

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..

 

[White Room]

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

 

[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