22mm chipboard

[larold]

Retiling bathroom floor. Have pulled up old tiles and floor underneath is 22mm green tongue and groove chipboard panels. Is it ok to just retile on top of these? I'm using porcelain 30 x 60 tiles.

 

[Richard C]

No, get rid of it; replace it with minimum 18mm WBP ply (you may need 25mm in some casses). Or overboard it with minimum 12mm WBP ply, properly fixed.

Also read the Tiling Sticky;
//www.diynot.com/forums/viewtopic.php?t=77709

& read the archive posts on this Forum before starting which will explain why.

 

[larold]

Thanks - and gosh
I really dont fancy pulling it all up. it will be a nightmare. They are big sheets and at the edges of the bathroom seem to run under the walls to the adjacent rooms. How would I cope with that? Do I just saw it out at the walls?
also I'm worried about raising the height if I put down 12mm ply as the tiles are 1cm thick too. Any other alternatives? I've read about 6mm tile backerboard. Can I use that?

 

[Lower]

Just take it out cutting it along the edges of the walls.

I've just done it in my bathroom and the floor is now much more solid and its wasn't that hard to do.

 

[larold]

thanks. wont that leave some areas overhanging the joists with no support?

 

[Lower]

That's where you put noggins in between the joists to support the ply.

 

[larold]

sorry, whats noggins?

 

[AlF2008]

they are the pieces of wood you put between the joists to provide strength and stability.

http://en.wikipedia.org/wiki/Dwang

 

[larold]

Ok thanks. The more I think about it, the more i think I'm NOT going the ripping up the floor route. So its either 12mm ply or what other alternatives? 6mm Tile backerboard? I have seen mention of nomoreply, marmox, wedi etc. Are all these suitable? to complicate things further, I am thinking about putting underfloor heating under the tiles. Does this change anything?

 

[gcol]

An expensive way around it is to use Bal Fastflex. It's a 2 part tile adhesive - basically it'll set like rubber and you can use it directly onto chipboard. Personally I wouldn't entertain chipboard anywhere near tiles, but fastflex is supposed to do the job.
EDIT: Just seen that Bal are doing a single part fastflex now. Be warned - it ain't cheap and it doesn't cover much per bag. http://www.trades-direct.co.uk/modules/shop/view.asp?Prodcode=sinpartfastflex

 

[larold]

Thanks. I'll investigate that. Just as an aside, why do builders put down chipboard flooring in bathrooms in the first place, if the recommended thing is to rip it up and replace it???

 

[Richard C]

Just as an aside, why do builders put down chipboard flooring in bathrooms in the first place, if the recommended thing is to rip it up and replace it???

Cos its dirt cheap, easy to cut & work with.

It does serve a purpose for general flooring but it’s not ideal for bathrooms & even the green stuff will eventually turn to mush with continual wetting. Chipboard will also start to flex & squeak after a few years in heavy use area like halls & landings & I’ve even know washing machines to eat their way though the floor after a few years due to vibration; it’s happened to me ! The main problem with it in bathrooms is that it’s not rigid enough to accept tiling & the only chance you’ll really have with it is to use something like Fastflex which gcol mentioned; but it’s bloody expensive by comparison & if it doesn’t work, you’ll have wasted even more cash!

 

[larold]

Thanks for your advice everyone. Very helpful.

 

[gcol]

Cos its dirt cheap...

No other reason necessary Richard. Though for the small difference in price for a small bathroom it'd be a good thing to use ply for this room only.

 

[SL]

I was unable to replace the green chipboard so I used Ditra Matting, as advised by my local tile shop. Tiles have been down just over a year and no problems so far.