Movement on tiles

[davphi338]

Hi,

I have just had my ensuite done. I've had electric underfloor heating installed and used Vysal 3mm insulation ( a bit like thin polystyrene) under the heating mat. The installer used flexible adhesive and grout but there is a lot of movement in the tiles, you can see the tiles moving at the edges. The grouting was completed today but it looks like it is already starting to crack.

I mentioned the movement to the installer and he said it can only be the electric heatimg mat wires pushing into the vysal insulation, he has never used it before and thinks this can be the only problem.

Has anyone else used vysal insulation and suffered from any problems.

The bathroom is only 1.2m by about 3.5m and the installer only used 12mm ply as the flooring, I had already taken the old flooring up. I mentioned that 12mm seemed a bit thin at the time and he said 12mm will be fine because it such a small area and my joists are close together.
The movement doesn't seem to be on every tile so I'm not sure if the problem is with the flooring or the fact that he probably didn't install the vysal insulation properly.

 

[gcol]

Sorry, shouldn't laugh. Your installer used 12mm ply straight onto your joists?! That's never gonna work!!
He should have use 25mm ply. Are you sure he just used 12mm straight onto the joists???? If so, you need to make sure that you don't pay him for starters.
Who paid for the materials?

 

[davphi338]

Hi,

Yes I'm sure he used 12mm ply straight onto the joists. I even said to him at the time that 12mm was a bit thin and I thought 18mm was the bare min. He assured me it would be OK because the joists were close together and it was only a small area.

I've paid him a £275 for materials out of a price of £1110.

The problem is, how do I resolve the problem now. Should I just refuse to pay him anything until he resolves the problem or hold back say 25% because he has also tiled the walls, installed new shower, shower door and aquapanel.

 

[joe-90]

That's plain crazy. As you say 18mm is the minimum. Also remember when he takes up the tiles and heating they'll go in the skip. When you put your 18/25mm ply down the height of everything will rise, the shower cubicle will have to be refitted as well as the pan and pedestal which means that wall tiles will need re-drilling and plumbing may no longer line up (toilet waste?).
Even the bottom row of tiles may need to come off.
It's a complete disaster.
There'll be no profit in this job for him.

 

[davphi338]

Well theres no way I'm paying for new tiles and heating mat. To be honest I'm not completely sure its the ply thats actually moving, not yet anyway. I can move some of the tiles just by putting pressure on two cormers of the tile with my fingers, I would need more pressure than that to move the ply even if it is only 12mm. To me its as if there are air pockets in the adhesive and the tile is rocking on the heating wire. I'm sure he's going to say its the polysterene insulation that is causing the problem. I suspect he has probably not used enougth adhesive. If I was installing the flooring I would have used a full bed of adhesive to completely cover the heating wires and then applied more adhesive with a notched trowel for the tile to sit on. I'm not sure how hes done it but somethings not right.

 

[joe-90]

I think you can forget the underlay being the problem as that will have been tested extensively prior to marketing.
If the tiles wobble to the touch then it sound like what you say, the tiles are resting on the wires and there is no real adhesion (as the adhesive will have gone off anyway). Either way the whole lot has to come up and if you take the whole lot up, skip the old tiles and heating, and put it back down on the ply - you may well get problems with the ply - and it'll have to come up yet again. (more new tiles and heating).
Take the whole lot up and lay it properly. If he won't do it then get someone else in to do it properly, pay the new guy and give the first guy whatever is left.

 

[gcol]

Regardless of the initial reason for the tiles coming loose, what is a given is that tiles laid on 12mm ply will come loose no matter what.

 

[davphi338]

Mrs just back home to find all tiles ripped up and heating matt screwed up in a ball. Fitter arrived back and just spoke to him on phone. He lifted 1 tile this morning and found that the insulation was not stuck to the ply ( he didn't read the instructions on how to stick it correctly). Anyway, he is now going to sandwich the insulation between the original 12mm ply and a 6mm ply so he doesn't have to stick it down. Hopefully the 12mm with 6mm screwed on top will give the extra rigidity required. All of this is at his own cost so he's not a bad guy just not clued up.

 

[joe-90]

Sorry that won't work. You MUST replace the 12mm ply with at least 18mm.

Not only will the tiles fall off worse than ever, but the heating won't operate as it should.

 

[davphi338]

Why won't the heating work, he is only going to sandwich the insulation between the ply not the actual matting. The heating matt will sit on top of the play. I take your point about the 6mm on top of 12mm not being very effective though.

 

[Richard C]

Just to reinforce what’s already been said; 18mm is the minimum if you’re sitting straight onto the joists (i.e.) no support from existing floorboards & you must fit noggins under any unsupported edges. Adding 6mm ply over 12mm will increase the rigidity but unless you glue the 2 together, it will never be as rigid as a single board 18mm thick; & making a plywood sandwich with the insulation between will further reduce potential rigidity. I also agree you will suffer a reduction in the heater mat efficiency; have you or your installer read the manufacturers installation guide? Failing to follow this may invalidate your heater mat warranty!

 

[gcol]

Don't be sandwiching the heating mat in ply. Just out of curiosity, how would he guarantee that he didn't screw through the heater cables?
As mentioned, unless you bond the two sheets together you will still have a grossly underrated tiling surface.
If and when you replace the floor, I recommend using 25mm WBP ply - 18mm is still a bit flymsy in my opinion. Oh and don't forget the noggins.

 

[davphi338]

Yes I've read the installation procedure for the Devi mat and I don't see any problem with the underfloor heating side of things, it will still be sat on ply and you don't have to put any insulation down if you don't want to. I do take all the points though about 12 & 6 mm ply screwed toghether not being as rigid as 18mm ply.

 

[Richard C]

I don't see any problem with the underfloor heating side of things, it will still be sat on ply and you don't have to put any insulation down if you don't want to.

Didn’t make myself clear; no you don’t have to put any insulation under the mat but it does make it more efficient & give quicker warm up time. If you sandwich the insulation between the ply boards, it will not directly reflect the heat upwards as it should so will be virtually ineffective, you may as well not use it.

The heater mat should still work OK but read the small print in the warranty, there may be something in them that will limit the full warranty to basic consumer rights if you fail to follow the installation guide; i.e. like rigidity of the floor & many don’t recommend tiling straight over the top but specify a latex based screed first to protect the cables.