What boarding for bathroom floor?

[Stewie56]

I'm in need of some help. We've had a major leak in the bathroom and the rotten old chipboard flooring (why is that stuff even legal in bathrooms?).
Various plumbers reckon I need marine ply, but it's hard to find and when I can it's bl**** expensive (between £50 and £75 +VAT a sheet).
Do I need marine ply or will WBP stuff do (18mm)? Are there different grades of WBP?
Wickes don't sell marine ply, but do sell structural ply suitable, they say, for external work (phone line not much help), so what is it?
B&Q offer a temperate hardwood ply (A decorative sheet material that can be used for cupboard doors units and shelving, suits vanished or stained finish.) at £63 a sheet, but with no other description - is it marine? Seems an overkill for doors and shelves at that price.
There seems to be a lot of conflicting advice out there on this topic. Given the difference in price (I may need about three sheets of 1220 x 2440) what do I REALLY need to use?
Help....

Quick update: just tried Wickes help line again and chappie said he had contacted the manufacturer (darn quickly, too!) and they say it's okay as a base for a bathroom floor but not as the actual floor. At under £30 a sheet it seems too good to be true. Probably is. Isn't it?

 

[xr4x4]

You could use mosture resistant t&g flooring?

Tbh anything, bar chipboard will be fine.

 

[mattysupra]

problem is no one knows what they are talking about.

You do not need marine plywood. You do not need exterior grade plywood either. There is no such thing as WBP ! (even tho B&Q etc list plywood as WBP.

The bathroom is indoors? so interior ? then you need a interior plywood. Simple.

You can use exterior but exterior means its dried to a higher MC content with a different glue bond. That glue bond being 'class 3'. You can also get interior plywood which is dried to a interior MC content that also has a class 3 adhesive bond.

Give a company called 'hanson plywood' a call and ask them what and where you can get it from. They will soon have you sorted.

 

[Stewie56]

Thanks for the replies, guys.

There's certainly a lot of guff out there on this, but I'll give the company you suggest a call and see what they have to offer.

Beginning to wish I'd never got into this in the first place, especially as the bl**** insurance company is now challenging the two quotes I've had.

Even the insurance surveyor 'expert' cited marine ply....

 

[dann09]

1. As above, the nonsense claimed for WBP ply in domestic housing is just that, nonsense.

2. Water and fungal damage will destroy any cellulose material, period.
No matter the material, once the floor, or underlayment, is water damaged, its damaged, & the tile or vinyl finished floor etc. will have to come up.

The limiting factor is how long before any "leak" is detected.

I have seen matching sheets of 3/4" ply and OSB sheet flooring equally swollen at the water damaged join. I have repaired hundreds of water damaged floors, roof panels & sheathing, sometimes all in one structure. The damage was equivalent, the material irrelevant.

3. Millions, if not billions of square yardage of OSB & chipboard/particle board has been fixed on floors and walls and roofs all over the world. Ply will soon be an expensive rarity.

4. However OP, if WBP is specified, then it has to be used.
But who exactly is doing your remedial insurance work - a contractor, or you?

FWIW: the building trades are full of these unexamined "myths" - such and such must be used or fixed a certain way etc. But who first said it must, where's the proof from experience or technical evaluation?

My thoughts are that someone, somewhere, is making money out of talking trash.

 

[mattysupra]

this might be of interest. Says the same as i said above with a bit more detail.

http://www.contractflooringjournal.co.uk/archive/helpdec03_2012.html

 

[dann09]

That is certainly of interest to me.

The OP could use whatever material suits, and the authority of the Journal to defend his/her choice if it was ever questioned.

 

[Stewie56]

Thanks again, all. Sorry for late reply - forgot my login details (doh!) and have also been battling with the insurance company - still! They.re using something software estimating package and being a royal pain in the rump and I'll end up doing the work myself as they are only offering half the value of the three quotes I've now had.
I value the advice and will not be using marine ply. Two guys have suggested chipboard (12mm?) topped with 6mm ply.
I'll probably go with interior ply, screw it to prevent creaking and facilitate future removal if needed and maybe tank it (if that's not an overkill?)
Thanks again for the advice - taken and appreciated!