Hi forum members

[Man2eep]

Hi,
I am looking for some advice, we have recently have had a extension done. The entire ground floor is wet underfloor heated. The floor is suspended floor joists with the pipe runs between the joists. A wpb ply board has been screwed down on the joists. The floor has then been tiled using 600mm by 600mm porclain tiles with a flexible adhesive. Soon after tiling and when the under floor heating was on, we noticed some tiles were loose, now over a span of a month loads of tiles have popped up and the grout cracked almost every where. What has gone wrong and how can we rectify this disaster ? Some people have said we should have used a backer board screwed to the ply and then tiled? Any assistance/guidance will be appreciated. Thanks

 

[Bubblecraft]

Hi & welcome to TF

 

[White Room]

Hi and welcome...how soon did you turn on the ufh after the tiles were laid.

 

[Ian]

Welcome along to TF. As per Whitebeam, how soon was the heating turned on, also, can you tell us whether the tiles have debonded from the adhesive or, has the adhesive debonded from the ply.

 

[Man2eep]

Hi, the underfloor heating was off during the tiling process, but as they finished tiling ,it was put on due to the cold weather. However I remember having come down some mornings and felt the tiles warm.

 

[Ian]

Most adhesive manufacturers state that heating should not be turned on for 28 days after the completion of the installation, this is to allow the adhesive to reach full strength. Also, it should be turned on at its lowest setting and then the temperature increased by one/two degrees per day so as not to 'shock' the floor. I'd still like to know if the tiles have debonded from the adhesive of the adhesive from the floor, a couple of pictures will speak a thousand words, if you can remove a loose tile or 2.

 

[Man2eep]

Hi Bri, the UFH went on as they completed the tiling process. As we walk over the tiles, some tiles are literally loose and seem de bonded from the adhesive. Later today I will lift up a tile and look to see whether the adhesive has de bonded from the wpb board.
Is it right to believe that porclain tiles should never be laid directly on wpb board. That there should have been a 12mm backer board screwed on the ply followed by flexible adhesive ?
thanks

 

[Ian]

Hi Bri, the UFH went on as they completed the tiling process. As we walk over the tiles, some tiles are literally loose and seem de bonded from the adhesive. Later today I will lift up a tile and look to see whether the adhesive has de bonded from the wpb board.
Is it right to believe that porclain tiles should never be laid directly on wpb board. That there should have been a 12mm backer board screwed on the ply followed by flexible adhesive ?
thanks

A 6mm backer board would have been fine 12mm is more for stud walls, the backer board would undoubtedly have been a better surface to tile to, also, the backs of the tiles should have been skimmed with adhesive as well as troweling the floor, this will help to achieve a full bed of adhesive and assisting adhesion to the tile. Just another thought, was the floor deflection (bounce) free after the ply was fitted? Is there any chance that excess movement has caused the tiles to debond?

 

[Man2eep]

Hi Bri, the substructure is on 9" joists with noggins. The ply is 18mm thick. Under the joists they put a course of brick to keep the joists tight. The suspended floor was/looked very rigid, there wasn't a bounce. I can only imagine as the heating kicked in it has warped the ply resulting in the tiles popping up. How can I send pictures. Thanks.

 

[Ian]

If you look in the reply box below, there is an icon with a tree in it, use this to upload pictures from your PC.

 

[Man2eep]

Ok will try to send pics,

 

[Man2eep]

Some pics View attachment 49200

 

[Ian]

Something has definitely caused the tiles to debond, to give you a definitive answer you will need to lift one or two to see what's underneath, I would imagine it won't be too difficult to remove a few of those.

 

[Man2eep]

Hi Bri, I managed to upload one pic, but am unable to do any more. Don't know why. Is acceptable to send some on your email address
thanks

 

[Ian]

Hi Bri, I managed to upload one pic, but am unable to do any more. Don't know why. Is acceptable to send some on your email address
thanks

I can see, 3 pics now. Have you lifted any tiles yet? If you need to send them to my email, please do, I can post them for you.

 

[stephenoneill]

heatshock :no backerboard used and tiles not backbuttered; probably looked great for the first week;tile theory is important:

 

[DHTiling]

Hi , you have a system that is heat and timber ... these 2 factors together create high thermal stress on a tiled installation.

This can be overcome with the use of an Elastomeric adhesive or the use of and Un-coupling membrane..

Normal C2FT/S1 is not suitable IMO and the use of C2FT/S2 min is required... but there is still risk of cracking due to the stresses of tiling to timber , this is where an Un-coupling membrane comes in and will take stresses of up to 3mm in expansion without cracking the tiling field.

So to your installation , it will most likely be poor choice of installation materials , factored in with the heating not being commissioned according to BS5385.. you should have been informed of these points before being allowed to just turn the heating on, cold or not..

The route now is to remove all tiles and clean the substrate ready to tile correctly and commission properly after installation.

 

[Man2eep]

Hi David,
thanks for your reply. What is a de coupling membrane. The codes you have specified, what are they ?
please if you can give specific make names of these items I can look into bringing the builder in back and discussing this with him.
thanks
.