New Limestone Kitchen Floor + electric UFH - Grout cracked after 24hrs - Tile Advice

barrysfloor · Oct 4, 2012

I'm hoping for some professional advice on what to do with my new Limstone tiled floor - I'm at my wits end!!

I had a job carried out in my house by local a tiler which completed 1 month ago - Sept '12; details as follows:

- New build house that we've lived in for 4 yrs since new.
- 40 sq mtrs across 3 adjoining rooms - utility, kitchen, family room.
- Exisiting floor is a floating subfloor on a concrete slab - no joists, rigid board insulation, 18/22mm chipboard and 5mm ply
- Vinyl was lifted, existing 5mm ply left down, 9mm WBP far eastern hardwood ply on top, screwed with 30mm screws at 6 in centres by experienced joiner - floor felt very solid after this work..
- Floor sealed and prepared - rolled on acrylic floor primer.
- 21sq mtrs of electric underfloor heating mats laid and installed by qualified electrician - work fine.
- 16 bags of BAL rapidset flex adhesive and 4 x BAL flexible grout.
- Tiles are limestone 400 x 600 x 12 good quality.
- Tiles were quite wet going down - moisture meter read 30-40%. Tiles have been grouted and sealed.

Even over the weekend cracks appeared in a number of places mostly around corners but some along long edge even across adjoining tiles. UFH had not been turned on at all at that stage and was not for 2 wks. Some tiles are visibly bouncing when stepping on edges by 1mm sometimes - looks like the bond is not good. Tiler is well regarded and experienced but stumped. Is looking to put it right thankfully but now 1 month on and no sign so very concerned.

No tiles lifted yet. UFH has been turned on now and is not materially worse for it.We are facing a rip-up and redo. Tiler says his insurance won't cover it.

Not sure what to do - tiler blaming substrate, joiner believes this to be fine, afraid of damaging UFH - not sure about how a repair will go. I've paid for all materials circa £3K - I am withholding labour payment until job put right.

Thanks All at tilersforums,
Barry

Ian · Oct 4, 2012

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

Welcome to TF Barry. The problem is without doubt the floating subfloor, not a suitable surface to tile especially with a soft stone. Have you lifted any of the loose tiles to see what the bond is like between tile and subfloor? Also, was a levelling compound used to cover the heat mat before tiling, or did the tiler tile directly onto the heat wire?

barrysfloor · Oct 4, 2012

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

Hi Brian, thanks for your prompt response.
No tiles lifted yet - tiler is due back to check any day supposedly.
In my mind the bond does not look good and I think they might lift up OK.
No levelling compound used, just the UFH mat and then bal flex adhesive on top and through the mesh backing. Any concerns with the moisture of the tiles affecting the adhesive bond?
The trades people are all mates and very experienced joiner, tiler and electrician who have installed floors for most of the area including a travertine floor in my sister in laws house a couple of years back that still perfect with UFH too.

Ian · Oct 4, 2012

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

I'd wait and see what you/tiler/joiner find when you remove a couple of tiles, I've seen a similar floor makeup recently that had also failed (marble in this instance), floating floors are so unstable that all the prep in the world won't stop a failure happening. I hate to see this sort of thing happen to people and I'm afraid there really isn't a solution other than, take the whole install out, remove the floating floor, then install a suitable substrate such as concrete etc.

John Benton · Oct 4, 2012

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

Brian's on the money there. The floating sub-floor is always a recipe for failure. I will not tile on them because it will fail almost certainly in time. Have turned down some really nice jobs because of this type of floor where the builder has fitted the floor and said it is ok for tiling on. I just would never take the risk because ultimately the tiler will get the blame.

Just as a matter of interest, what was the sub-floor at your sister-in-laws house?

barrysfloor · Oct 6, 2012

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

I believe my sis-in-law floor is supported with joists as it is raised and there are breeze blocks on the outside around the perimeter.
Until a couple of tiles are lifted, it's pure speculation as to what the root causes are. Best case, the tiles lift ok, the subfloor is sound and the mats are intact and stuck to subfloor. The issue is not widespread across the floor, there are some large sections where there is no cracks at all. The kitchen area is definitely the worst, prob as its trafficked the most. Also one section prob 10sq mtrs is perfect - this happens also not to have the UFH mat under but was also tiled about 5days after the the rest of the floor so tiles were much drier going down. Replacing the substrate is defo not an option and will be devastated if the tiles have to be taken out and binned.

I'll repost some pics of the tiles once lifted.
Thanks again for your advice.

kilty55 · Oct 6, 2012

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

hi barry unfortunately if its a floating floor its a risk as well as the fact 9mm ply was used 9mm ply is not suitbale imo although i am aware many people use it

Just Rizzle · Oct 24, 2014

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

never used ply for over 10 yrs preperation was all wrong from the start bound to fail. shouldof layed ditra matting then screeded then the elec mat then screed again then fix with flexi adhesive andbutter back of tiles done this method for years tied and tested no failes to date.

nybor62 · Oct 25, 2014

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

oh dear . floating floor's nightmare , 9mm ply no good imo . and i would have latex over the ufh. not tiled directly on top off it

see what your tiler says , he will probs say ive done loads of these with no prob, well he has a prob now

good luck

widler · Oct 25, 2014

Re: New Limestone Kitchen Floor + electric UFH - Grout cracked after 2

I bet after over 2 years the floor is no more chaps

nybor62 · Oct 25, 2014