How do I stop this happening again?

[indus]

About six years ago I had a new floor laid in my kitchen. The tiles were made from limestone and the tiler wasn't happy with my choice of tiles and was worried about them cracking. And crack they did after about a year!

The floor is a timber suspended type


The floor is being ripped up now anyway because I'm having an extension built. The pics below show the floor and it looks to be 18mm ply over the floorboards and I know the tiler used flexible adhesive.

My question is how do I prevent this happening again?

 

[footprints]

I don’t claim to be an expert but, the joists don’t seem very well supported on just that little leg, I would have thought brick piers would have been better.

 

[indus]

I don’t claim to be an expert but, the joists don’t seem very well supported on just that little leg, I would have thought brick piers would have been better.

Thanks mate. They were supported on a pier but they've been cut back because of other work I'm having done.

 

[tpt]

Footprints is right - looks like too much flex in the substrate. Add some support extra support across the span, then overboard with a product called no more ply, then use a flexi adhesive

 

[tpt]

Also you may find that the cracks follow joints in the ply

if your not sure, measure the size of the joists and the length of the unsuppored span

 

[Happyplumber]

Ditra matting and 25mm ply screwed down using good quality passivated screw

All joints to have noggings and finally finish with Ditra matting and a good quality flexible adhesive

All tiles to be bedded down correctly using a notched trowel Butter the back of the tile as well as the floor,thus making sure of a good contact between the floor substrate and the tile

If you follow this ,the tiles will definetly not crack

 

[tpt]

happyplumber is right, but ditra isn't usually required unless you've got lateral movement.
I'd take the existing stuff up and see what the issue was, my guess is that the big long crack follows a joint in the ply, and that its not been supported underneath with a joist/nogging

 

[Happyplumber]

I know I am right and the process i wrote is belt and braces