Tiling on water resistant chipboard

[SJPurdy]

Here Steve have a look at this mate.
Anti-fracture Matting for Floors Subject to Limited Movement | Tilemaster Adhesives

Thanks for the link. It is the same with countless other manufacturers with their anti fracture/decoupling membranes, they are designed to do a job and allow for (the unspecified) "limited movement" in the substrate. I admit I am a bit sceptical (hence my earlier post) as they have been around in various forms for years and I have seem them not cope when presumably the movement exceeded the "limited movement".
I also note that many manufacturer's have designed tile adhesives to fix directly to the boards. The rubber crumb type for example cure to a bed under the tiles that will also allow for limited movement; but I along with earlier posters in this thread would not recommend this method (even though I have fixed many floors this way with no problem).

The key with the floor under discussion is to make sure it is firmly screw fixed down to the joists so that the floor is rigid with no discernible movement and that any joints are supported. The original poster can then choose from the methods given above as to how to prepare for retiling. If height is a major issue then the decoupling/anti-fracture membrane way will be the thinnest. Personally I would prefer to overboard with 6mm Hardie backer board (fixed to manufacturer's spec) because I perceive that this gives some increase in rigidity to the floor. I would also consider 6mm "no more ply" (fixed to manufacturer's spec) but only if the surface of the chipboard is very flat.

 

[Old Mod]

Thanks for the link. It is the same with countless other manufacturers with their anti fracture/decoupling membranes, they are designed to do a job and allow for (the unspecified) "limited movement" in the substrate. I admit I am a bit sceptical (hence my earlier post) as they have been around in various forms for years and I have seem them not cope when presumably the movement exceeded the "limited movement".
I also note that many manufacturer's have designed tile adhesives to fix directly to the boards. The rubber crumb type for example cure to a bed under the tiles that will also allow for limited movement; but I along with earlier posters in this thread would not recommend this method (even though I have fixed many floors this way with no problem).

The key with the floor under discussion is to make sure it is firmly screw fixed down to the joists so that the floor is rigid with no discernible movement and that any joints are supported. The original poster can then choose from the methods given above as to how to prepare for retiling. If height is a major issue then the decoupling/anti-fracture membrane way will be the thinnest. Personally I would prefer to overboard with 6mm Hardie backer board (fixed to manufacturer's spec) because I perceive that this gives some increase in rigidity to the floor. I would also consider 6mm "no more ply" (fixed to manufacturer's spec) but only if the surface of the chipboard is very flat.

Must admit Steve totally agree, I do struggle with the idea that these ultra thin mats can cope.
Having attended Schluters wet room course and seen video evidence on how Ditra works I've a lot of faith in it but that's considerably thicker and I can visualise how it works, 0.85mm thick mat is somewhat harder to see, but I'm sure it works just fine.
My first choice would be hardie all day long, however the op insisted that even that was too high!
Hence the suggestion of the thinner type mats.
No more than that really.

 

[trustiling]

Tiling on to chipboard would be fine if you knew that the joists were 300mm centres (which they are never, nearly always 400mm)
But the problem lies where they are tongued together they rarely if ever have dwangs here which will always cause to much deflection.

As above lift the carpet back and lay some thin timber under there with a little screed or something to smooth it out and use 6mm hardie or similar minimum.
The only time I would use Ditra if I absolutely had to would be if the floor was doing in mosaic.

 

[Dave]

It's not the adhesive sticking , it's chipboard as in a product , it's not stable enough to tile too directly and expect long term longevity IMHO ...

 

[Dan]

If it's that green stuff, it's meant to be compressed under heat similar to ply, with polymers in it etc, so is meant to be okay.

But I thought overboarding it with ply was the way we recommended it on the forum. Just because we're all so uber.

 

[Dave]

If it's that green stuff, it's meant to be compressed under heat similar to ply, with polymers in it etc, so is meant to be okay.

But I thought overboarding it with ply was the way we recommended it on the forum. Just because we're all so uber.

We all know how ply reacts when subjected to prolonged wetting , say from a leaking toilet that doesn't get noticed lol lol ..etc..

The green chipboard is the moisture resistant one but it's still prone to swelling ...

At the end of the day , if anyone feels confident tiling direct and offers a guarantee , then that's that particular fixers choice and method ... We can only offer pro/cons of tiling to certain substrates..

 

[Ivan Rubery]

You chaps are brilliant for help and advice. I have decided to get rid of the 18MM chipboard and replace with 18MM WBP plywood. I will feel more confident in the installation

 

[trustiling]

Ivan, replacing the floor with 18mm ply will not solve the issue unless the joists are at 300mm centres (which they won't be) and you are going to dwang everywhere joins are very time consuming job.

We have been tiling on top of green or brown chipboard for years but always with another substrate on top whether that was 6/9/12mm plywood through the years cross laid for support screwed at 200mm centres or annular nailed. Now 12mm is seen as the minimum if still using ply but 6mm hardie or insulation board the minimum. Just so we are clear I haven't used 6mm ply for over 14 years lol

In short, you as the tradesman have a duty to advise the client of what is the standard when laying tiles to existing substrates regardless of their expectations.
What are you going to do at the edges of the room when you find out that a full sheet of chipboard goes under a stud wall into the adjacent room??
You will be compromising the integrity of the whole floor needlessly when you have been given countless other recommendations by qualified persons on this forum. Sorry to sound like this but the customer doesn't always know best.

 

[trustiling]

I have put down plenty new chipboard floors to builders spec and you can clearly see deflection where tongued and not dwanged even when loaded with glue, this is why we always cross lay another substrate on top...not because the chipboard isn't suitable for the adhesive, hell this new rubbish will stick to metal and glass. But for structural purposes, you could lay another layer of chipboard the other way and tile directly onto it no problem.

6mm hardie....make a shape of 6mm between you index finger and thumb in front of your face and then tell yourself you are going to rip up a perfectly good floor for this height difference and so much more material and labour cost for no structural gain.

 

[Ivan Rubery]

Hi Trustiling, OK I understand your very valid point of stud wall going into another room. I will go with the advice of placing ply on top of chipboard. Thankyou.

 

[Martyn Leeds]

We going with the 9mm ply then?

 

[widler]

Id use HARDIE not PLY , much more stable ie it will not swell if it gets wet or when hot or cold
Marine ply will move as well.

Ps timber with move a tad even with the water in the addy when drying out

 

[SJPurdy]

Now 12mm is seen as the minimum if still using ply

I think that is 15mm ply now (but i'm not sure!).
As I understand it if new floor 300mm c/c joists noggins so that can fit new 15mm (min) ply. If exist floor with joists up to 400mm c/c then can overlay with min 15mm ply fixed at 300mm screw spacings or an equivalent tile backer board (6mm Hardie, 10mm Wedi etc). These for fixing ceramic tiles not stone. It would be useful to everyone, I think if this is corrected if wrong!

A note on the water getting into wood and causing it to swell: even if overlayed with a water proof tile backer board a leak under the bath can still get into the wood floor base and spread under the tile backer board causing it to swell and lift, thus cauasing tiles to crack (usually) at joits in the backer board. This has happened to me and required 150 mile round trip to replace the tiles.

 

[Ivan Rubery]

Hi mate,

I always use Schluter ditra matting on good chipboard floors with very little or ideally no deflection stuck down with ardex AF200 but if there is too much movement there then I would definitely go with a 6 or 9mm backer board glued, screwed & taped and if there is a bit of a step coming into the room I always use some thin layers of underlay to create a bit of a ramp if need be.


Hope that helps

Hi there

How is the backer board fixed, you mention glue, would that be gripfill, or should I be reading this as floor tiling cement ?

Cheers

 

[John Benton]

Yep tile adhesive, floor cleaned and primed prior to this and spread addy with 6mm notched trowel and then screw down to secure. The screws hold the board in place, the adhesive fills any voids underneath.

PS Don't forget to make sure the screws are shorter than the combined thickness of the backerboard and chipboard, generally 20mm screws are fine