Floor tiling onto chipboard. Does it need another surface?d

[saveasteading]

We have 3 areas of upper floor to be tiled for en-suites? They are t&g chipboard screwed to timber joists.

Concerned that cracks may form at joints and that chipboard is  itself suitable as a tile substrate.

We are thinking of Wedi board or Hardiebacker as a waterproof material that will also prevent cracking. Expensive though.

The joists are substantial and don't appear to bend or bounce at all

 

Any advice please?

 

 

[nod]

There’s all sorts of backer board you can glue and screw down 

The majority that I do are done with Ditra Matt glued down Quick and easy 

and bombproof 

[Moonshine]

I have just been through this process

 

We did 6mm fibre cement board tile adhesive and screwed down, with the option of the ditra matt.

 

Tiler turned up and was happy with the prep and didn't feel he needed the Matt.

 

Tiles are going down this week so won't know if there is an issue for a long time

[saveasteading]

Thanks. I've seen the matting at tops and assumed it was for problem concrete. That looks easy enough to glue to the chipboard. Strangely topps seem to have 3 different products doing much the same.

Same sort of price as hardiebacker /m2.

 

It is also recommended for ufh screeds which seems counterproductive....why add an insulating layer? I have loads of tiling straight onto concrete, with no issues...as long as it is old perhaps.

[Moonshine]

1 hour ago, saveasteading said:

Same sort of price as hardiebacker /m2.

 

I used 6mm Allshield Tile Backer and got it for £5.90 + VAT a sheet (1200 x 800mm ~1m2)

 

https://sound-is.com/products/allshield-tile-backer/

 

Labour was straight forward as you can cut it with a couple of scores of a sharp knife and bending it, and screw down to it without pre-drilling, heads stick up a bit but nothing major.

[Nickfromwales]

11 hours ago, saveasteading said:

We have 3 areas of upper floor to be tiled for en-suites? They are t&g chipboard screwed to timber joists.

Concerned that cracks may form at joints and that chipboard is  itself suitable as a tile substrate.

We are thinking of Wedi board or Hardiebacker as a waterproof material that will also prevent cracking. Expensive though.

The joists are substantial and don't appear to bend or bounce at all

 

Any advice please?

 

 

I've NEVER once used backer-board when tiling over timber floors, ever. Never had a single crack / failure / issue and I've been tiling for north of 25 years.

Plywood, glued and screwed, is absolutely bombproof AFAIC, and I actually dislike backer board because it doesn't conform to undulations like plywood does. If the sub-floor is "wonky" you also have to set the backer-board down into flexible tile adhesive, and screw it, so I'm not a fan.

 

6mm ply or even 4mm will suffice, and I only ever use thicker if I'm trying to match adjoining floor thresholds etc.

[Nickfromwales]

You'll want 5 screws per chipboard deck, per joist, minimum. If not, add more before ply'ing.

[saveasteading]

5 minutes ago, Nickfromwales said:

Plywood, glued and screwed

Normal plywoood? Waterproof? I guess any will stand a bit of damp whereas chipboard acts as a sponge. 

Not that i've ever worried about it before, but on the off chance that the floor gets soaked or a joint leaks.

 

That makes sense about the ply moulding to undulations. I have used hardboard, but if you say ply, then ply. £8/m2 is good news too.

 

Have you tried ditra or similar matting? Anything you dislike apart from the price?

 

Good point about the chipboard screws.  One chance.  A hands and knees qc session is required.

 

[Nickfromwales]

7 minutes ago, saveasteading said:

Normal plywoood? Waterproof? I guess any will stand a bit of damp whereas chipboard acts as a sponge. 

Not that i've ever worried about it before, but on the off chance that the floor gets soaked or a joint leaks.

 

That makes sense about the ply moulding to undulations. I have used hardboard, but if you say ply, then ply. £8/m2 is good news too.

 

Have you tried ditra or similar matting? Anything you dislike apart from the price?

 

Good point about the chipboard screws.  One chance.  A hands and knees qc session is required.

 

Normal plywood. Tanking with a liquid tanking solution or membrane ( if you're rich ) in known wet / splash areas is a no-brainer, so sense always prevails.

 

I've used Ditra etc where it's been a dodgy screed ( laid by other and I've not laid it ) and brilliant results. I've only ever used Ditra once over chipboard, and that was in communal flats where the chipboard floors were all non-mechanically fixed ( zero screws whatsoever ) for acoustic control. Every single other job has been plywood, without a second thought.

[Nickfromwales]

1 hour ago, saveasteading said:

A hands and knees qc session is required.

Best time you'll spend, as the floor will only be as good as the deck it sits on.

[saveasteading]

Recommended tanking product? Adhesive has to stick to it.