Jackoboard Prep and tile wobble

[Alex Jungius]

Hi,

We're just in the process of getting a new kitchen fitted and have had large 750mm square porcelain tiles laid and grouted. Only issue is that a few had a bit of a wobble on them a week or so after being laid and grouted. They came back, relaid the tiles in question but a week later there is the same issue with a few of them. We're at our wits end!

The floor is a ground floor above a basement so wooden floor boards which were pretty stuff as was then 12mm plywood then 6mm Jackoboard. The only thing is that the jackoboards were only screwed into the ply/floorboards with washers rather than any adhesive used. They also weren't taped along the joins. Could this be the issue or have the tiles been poorly laid or the wrong adhesive/grout used. They are both flexible and from Benfer.

Oh, and we have electric UFH under these tiles so every relay feels risky.

Thanks in advance.

 

[WetSaw]

Any pictures when the tiles were taken up?

 

[John Benton]

Sounds like a disaster waiting to happen. What was the process of laying the floor, from the floorboards up?

This was one I looked at earlier this year, kitchen floor. The build up was plywood, electric ufh and then dot and dabbed 60x60 porcelain tiles. 50sq m needs lifting and all redoing and the kitchen is sat on top of the tiles, island unit with granite worktops.

Don’t get the kitchen fitted over the floor until the problem has been rectified otherwise it will cost you a lot more money than it already will do

 

[Alex Jungius]

I don't have any pictures unfortunately as when the problem tiles were relaid we weren't in.

The process was existing floorboards, following by 12mm plywood followed by 6mm Jackoboard which was screwed down into ply/floorboards then UFH, followed by adhesive and tiles. I saw him do the first few tiles and it didn't look like dot and dab, pretty much the whole floor and tile was covered with adhesive. Unfortunately, the kitchen is already in as the wobble didn't start until after it has been installed.

The problem area is not near the kitchen units so I'm going to ask them to be relaid but should be re-look at the floor prep? Should ply have been thicker, should Jackoboard have had glue as well as screws?

Thanks

 

[Dumbo]

Sounds like a disaster waiting to happen. What was the process of laying the floor, from the floorboards up?

This was one I looked at earlier this year, kitchen floor. The build up was plywood, electric ufh and then dot and dabbed 60x60 porcelain tiles. 50sq m needs lifting and all redoing and the kitchen is sat on top of the tiles, island unit with granite worktops.

Don’t get the kitchen fitted over the floor until the problem has been rectified otherwise it will cost you a lot more money than it already will do

View attachment 100353

I like the fact they have ventilation around the cables to induce thermal convection to make the ufh more efficient

 

[John Benton]

The jackoboard should have had adhesive underneath and then screwed with washers. Next, the ufh fitted and that should have been encased with levelling compound. Firstly to cover the cable to eliminate it burning out and secondly to protect the cable from being damaged when putting a metal trowel across it. It should then be primed and tiled.

 

[Alex Jungius]

Yes, the jackoboard wasn't glued down, could that be whats causing the issues? The UFH said that adhesive over the cables would be fine without self-leveling however. It's strange it's only cracking in a few areas.

 

[John Benton]

Yes, the jackoboard wasn't glued down, could that be whats causing the issues? The UFH said that adhesive over the cables would be fine without self-leveling however. It's strange it's only cracking in a few areas.

There could be voids underneath the jackoboard, hence the reason for using adhesive as well as mechanical fixings. I suspect that the adhesive is not getting full coverage on the tile when fixed or that the tiles were not back buttered prior to fixing. I fear there are more reasons underlying, literally, that are the cause of these problems and this will be a continual battle until it is taken up and started from scratch