Grout starting to crack around floor tiles

[rl11tr]

Not long ago I had the existing water damaged downstairs bathroom floor replaced with a whole new chipboard floating floor – this was before considering tiling, so I realise it would have been better to fix the floor but too late now.

Having later decided to tile, the tile supplier suggested covering with 6mm No More Ply, priming it and using Ultra Tile Fix ProFlex SPES S1. The grout used was Mapei UltraColor-Plus to match what was used with the wall tiles. The whole floor has not been tiled - just the small visible area - 6 x 4 330mm square tiles.

The floor tiles have only been down for 5 weeks and already the grout is starting to crack and I can just about see deflection up and down of the tiles!

Is this simply because of the floating floor, or the wrong adhesive or the wrong grout – a bit of all perhaps?

What do you suggest as a way forward? A whole new floor would mean ripping out bath and fitted furniture etc!

 

[Dave]

Simply down to deflection in the floating floor. The suppliers should have advised against it.

 

[rl11tr]

Any thoughts on the way forward? Is there a grout replacement that would be flexible enough to cope? - cracks are hairline. Do I have to take up tiles and adhesive and use S2 (or something else) - presumably a nightmare to take up and certain to destroy floor! Or am I just knackered and will just have to cover tiles with lino!!

 

[Dave]

Tap the floor tiles, are they sounding hollow/loose. ?

 

[rl11tr]

Hard to tell from tapping sound - it's very echoey in the room - but I think a couple must be loose underneath as there seems to be slight up/down deflection just pressing and letting go on the corners

 

[Dave]

Sorry to say that has failed, no grout will fix it.

 

[rl11tr]

So tiles have to come up and be refixed with an alternative to S1 or tiling simply not an option? I thought No More Ply on a floating floor was supposed to be OK?

 

[Dave]

So tiles have to come up and be refixed with an alternative to S1 or tiling simply not an option? I thought No More Ply on a floating floor was supposed to be OK?

I don’t know who told you NMP is ok for floating floors but if you have deflection then it simply won’t strengthen it sufficiently.

 

[rl11tr]

STS site says "6mm PrePrimed NoMorePly strengthens timber floors before tiling. They prevent tiles and grout lines cracking by removing the ‘flex’ in timber floors caused by footfall. Slim 6mm boards provide the same strength as 15mm plywood and so reduce the ‘step’ into the tiled area."

I was actually going to risk tiling direct onto chipboard with S2 but thought I'd play it safe and use NMP.

Wish I'd gone with S2 now.

Though really wish I had a fixed floor

 

[Dave]

Timber floors ( joists ) and floating floors are totally different. To tile any timber floor you need to virtually remove deflection. With a floating floor this is virtually impossible unless you use say 25mm ply , that can reduce deflection in the majority of a floor but they tend to still flex at the perimeter.
Your understanding of the wording timber floor doesn’t include floating floors I’m afraid.

 

[rl11tr]

So any thoughts on a way forward?
Attempting to get all the grout, tiles and adhesive removed will surely destroy the NMP and chipboard?
I can only think to just leave and see how bad it gets and maybe lino when it gets really bad!

 

[Dave]

That’s your choice, sometimes on smaller floating floors, you can use longer frame fixings and pull the floor down tight to the substrate to remove bounce. Then tile with nmp again and S2 adhesive and a highly modified grout.

 

[rl11tr]

That's a good idea. Have used long frame fixings to level with laminate before. Would have been easy to do before tiling

 

[Garyo]

Just throwing in an idea ! Is this floor going to get light traffic, and is it your own home ? If so then there is another way…..rake out and vacuum all the old grout and replace with silicon mastic. All the movement that you had will remain but the joints won’t open up, and water won’t get into your floor. It will need to be light traffic though ! And take it easy with cleaning….

 

[Jon591]

Any thoughts on the way forward? Is there a grout replacement that would be flexible enough to cope? - cracks are hairline. Do I have to take up tiles and adhesive and use S2 (or something else) - presumably a nightmare to take up and certain to destroy floor! Or am I just knackered and will just have to cover tiles with lino!!

You need a mastic joint matching grout colour around the floor to wall junction.
Should always have all tile to tile junctions siliconed anyway, as regardless of what they are fixed to, the grout always cracks and falls out as it’s not flexible

 

[rl11tr]

You need a mastic joint matching grout colour around the floor to wall junction.
Should always have all tile to tile junctions siliconed anyway, as regardless of what they are fixed to, the grout always cracks and falls out as it’s not flexible

Yes; floor to wall junction is siliconed and not a problem - there is only about 1m of floor to wall anyway

 

[rl11tr]

Thanks for all of the help

Thought I'd put up a photo to show what it looks like. The whole tiled area is only 2m x 1m. It's really just used as a cloakroom but happens to have a bath with shower over, in the room too. The hairline cracks are really hairline - wife can't see them but they are definitely there and there is the tiniest movement up and down if I press a couple of the tile corners. Cracks are only across the 1m width too. I'm thinking best to leave for now but take up tiles when they do come loose and screw down chipboard into concrete floor underneath. Then use more flexible adhesive and grout. I think I'd have probably been OK if I'd gone for S2 and a flexible grout in the first place. The Ultra Tile Fix ProFlex SPES S1 supplied seems to be like concrete with zero flex and the Mapei UltraColor-Plus grout doesn't mention being flexible at all.

 

[Jon591]

Yes; floor to wall junction is siliconed and not a problem - there is only about 1m of floor to wall anyway

Ah sorry I misread the original post and assumed as it usually is that the crack was around the perimeter,
The tiler should have used a flexible adhesive and grout if not you will have this problem. If the tiler did follow correct instructions then as suggested your sub floor is the issue, and with that I can’t give a helpful suggestion