Sub floor for bathroom

[stephen_lowfield]

Hi, I am currently doing a self build extension on my bungalow half of it will be making the bedroom bigger which I will be using 22mm Chipboard and the other half will be a family bathroom. For the bathroom I am looking at tongue and groove plywood as we had a leak in our old house and that was chipboard and went all mushy and had to be replaced. So going plywood as it is more structural sound and more water resistant.
My question is where is the best place to by 22mm t&g plywood as I am seriously struggling to find this.

 

[accelerator]

Will you be buying marine grade plywood?

 

[stephen_lowfield]

Will you be buying marine grade plywood?

Hi accelerator I was thinking of this as it’s the only one I can really find for t&g

 

[mrrusty]

Use this. To all intents it is totally waterproof. I inadvertently did a test - left an offcut outside in the rain for 6 months, then found a use for it. Trimmed off the T&G and the core was bone dry. It hadn't delaminated, twisted or warped. https://www.cwberry.com/kronobuild-p5-fast-shield-tg-chipboard-flooring-2400-x-600-x-22mm

 

[cdbe]

I think it's all (flooring grade t&g chipboard) water resistant these days.It should survive long enough to notice and rectify any leak.

If it's ground floor have you considered solid or B&B?

 

[simplesteve]

Have you looked at No More Ply in T & G ?

 

[stephen_lowfield]

Use this. To all intents it is totally waterproof. I inadvertently did a test - left an offcut outside in the rain for 6 months, then found a use for it. Trimmed off the T&G and the core was bone dry. It hadn't delaminated, twisted or warped. https://www.cwberry.com/kronobuild-p5-fast-shield-tg-chipboard-flooring-2400-x-600-x-22mm

Thanks mrrusty looks very similar to the Egger protect. I will have a look into this.

 

[stephen_lowfield]

I think it's all (flooring grade t&g chipboard) water resistant these days.It should survive long enough to notice and rectify any leak.

If it's ground floor have you considered solid or B&B?

Thanks cdbe. Extension already built and I wasn’t aware of B&B at the time and I went for suspended so I could hide all the plumbing and it was easy maintenance if anything happens in the future.

 

[stephen_lowfield]

Have you looked at No More Ply in T & G ?

Thanks simplesteve. Not heard of no more ply. I will have a look into this.

 

[Ivor Windybottom]

I did my bathroom with Wickes 22mm water resistant chipboard. I've been using the offcuts as formwork, covering and ramps outside ever since for years and they're surviving all kinds of weather.

 

[kp00110]

For my ensuites upstairs (timber floor joists) we used some of this from Selco https://www.selcobw.com/dryguard-water-repellent-plywood-fscr and not had a single issue - floor is solid as can be and zero flex. So tiles have been down almost 2 years and feel like their on concrete. We used tongue and groove boards for another part of the upstairs extension which is only carpeted, and despite glue and screwing down very well it still does squeek and flex - which makes me glad I didnt use the 600mm wide boards for the bathroom! Maybe its all the joints

 

[Ivor Windybottom]

I should add I didn't tile mine, I used commercial vinyl flooring. I don't know whether you could tile onto 22mm chipboard, probably not.

 

[simplesteve]

No, you can't tile chipboard. It's not good practice to tile ply either, though it can be done.

 

[yorksbuilder]

Use a thinner floor board and overlay with 6mm no more ply. Or buy 22mm TG4 no more ply if you want a solid all through cement board floor

 

[Deluks]

For my ensuites upstairs (timber floor joists) we used some of this from Selco https://www.selcobw.com/dryguard-water-repellent-plywood-fscr

My reservation with this would be adhesion. Using a water based adhesive on a waterproof surface sounds counterintuitive, did you use a decoupling membrane?