Dry lining on wonky wall and order of materials

[dave_104]

Hi
I'm going to be dry lining a brick wall for a bathroom, and wondered if anyone had some advice about any part of what I'm going to be doing?

The brick wall is external and non-cavity, and on the inside I plan to fit battens, ply, celotex and then put 10mm plastic wall boards up.

So far I've battened it out (treated on DPC strips). My concern is that the final plastic wall boards will need to be dead flat and straight otherwise it'll look visually bad, and the brick wall isn't particularly straight so I've shaved and packed the battens as best as I can to straighten it out a bit better. It's still not perfect and so for the next stage I'm planning to put 12mm ply directly on the battens, and then 50mm celotex on the ply, with the plastic wall boards gluing on the celotex. (I wasn't sure if it's better to put the ply after the celotex instead??).
By putting the ply first, it seems I've got the ability to further correct any dips/bends in the wall as I was thinking I could pack it out more prior to fitting the insulation boards.
The reason for the ply was also to add some rigidity to the wall, as the plastic boards are quite flexy and I'm trying to avoid any sagging if someone leans against a section of wall which is in-between the battens.

Holding it all together was another question - so the ply is obviously screwed to the battening, and I guess the celotex gets glued to the ply, and likewise the plastic wall boards glued (or siliconed?) to the celotex foil.

Does that all sound normal and ok or would anyone have any suggestions please?

Cheers,
Dave

 

[Mr Chibs]

I wouldn’t put the ply behind the insulation.

I fitted 2x1 battens, and packed these to get them flat, celotex on top, then plasterboard. (you could use ply if you wanted)

Plasterboard will be cheaper than plywood. and you could just joint The taper edges together.

what’s the plastic covering you are using?

 

[dave_104]

Hi Mr Chibs

Thanks for your reply. I was going to use moisture resistant p/board but then decided on the ply as it'll be better hanging things from and as a bonus the offcuts will be used on the floor! I think you're right in saying ply on top of the insulation and it'll also mean less fixing (so I can screw right through insulation to the batten work and sandwich the lot together), and will be nearer for things that hang off the wall (without 3" screws for loo roll holders etc!). I reckon I might then paint the ply in SBR to avoid any water seeps causing problems (maybe a bit over the top I guess but it wouldn't take long to do).

The plastic is Cascade shower panels, I assume they're UPVC and hollow core, they're 10mm. Manufacturers say to roughen up the back to give a key before gluing. A lot say no solvent glues as it might melt through the panel (?) and so I was half thinking of siliconing the plastic panels to the ply. I don't have much success with Gripfill unfortunately and it stinks for a real long time!

 

[Mr Chibs]

You can get solvent free adhesives, there is a grip fill one like that as well as a hundred others.

I think solvent free ones are suited to foams and plastics. have a read up to be sure.

I’ve been using Puraflex from Toolstation, it’s very strong, but takes a while to cure. I’ve been sticking fibreglass to anything with it!

50mm celotex screwed time battens will be pretty robust, you might be surprised.
Get some aluminium ducting tape 75-100mm to cover the board joints. I filled any gaps with expanding foam first.

good luck.

 

[^woody^]

Does that all sound normal

No

You batten the wall, spaced to suit the plastic manufacturers guidance, and pack the battens out to be vertical and inline horizontally.

Then either insulate between and across, or just in between before fitting the plastic.

I can't see why you want to fit ply unless the plastic manufacturer says to do so. If they do just follow their guide.