plywood behind plasterboard behind bath and shower

[fastedd]

Hi there. Been lurking a while, gaining the knowledge and haven't needed to post until now.


I'm repairing / replacing the stud wall in my bathroom, its only 900m wide and is used to cover the soil pipe and plumbing and to space out the room to 1700mm so the 1692mm bath fits snug end to end across the whole room.

On this wall there will be a few things hanging off, shower screen, shower rail, bar mixer shower fixing kit, bath edge support etc.

Instead of putting in lots of noggins and trying to fix everything now is it possible to do the following:

Turn my 45 x 70mm upright studs sideways and set back 18mm from the floor and ceiling plates. Then fix 18mm wbp plywood across the wall so the plywood is flush with the top and bottom plates. Then cover with the MR plasterboard This will then be finished with multi-wall laminated plywood finish.

Then I don't have to worry where to screw any of the shower fixings, screen fixings etc. I will always be going through 11mm multi-wall, 12.5mm plasterboard and 18mm wbp ply.

Is this a daft idea. Am I doing something wrong that could cause problems in the future?

thanks...
Ed

 

[pinenot]

Could you not apply the 18mm (wpb) ply directly to the existing studs, also the top and bottom runners, apply a waterproof membrane to this and affix the finishing ply to this. I feel this would be much easier than your proposal, but should you insist on this just move the existing studs back from the the existing frame and fix some 1" thick trimmers 18 mm back from side frame members to create a pocked to accept the ply flush, because the ply can support itself quite well...pinenot

 

[foxhole]

Osb would suffice,or aqua panel, why the plasterboard , just introduces a weakness to fail.The laminated ply is strong enough for fixings on it's own.

 

[fastedd]

Thanks for the replies.

Old wall does not exist, I pulled it down to replace ceiling and warped chipboard floor. Not a big deal to pull down, top was only held in with two nails into the plasterboard ceiling, no wood above and only one nail halfway down one side. Also it was so out of square the run out on the end of the bath was 5mm to 35mm over the 700mm width.

The wall needs to have plasterboard as the wall extends past the bath shower screen to the side of the window and carries on below the window hiding the plumbing for the toilet and sink. Unfortunately I cannot set it back further as it is already hard against the soil pipe.

I think Ill do what pinenot suggests, build the wall as standard and use some 19mm x 32mm trimmers to sink the plywood in flush with the frame.

cheers guys
Ed

 

[stevenn21]

i would use marine ply i dont know if laminated is the same thing or not

marine ply is a lot more expensive but better protection than ordinary ply when used in this setting

 

[fastedd]

It worked out ok in the end. I used 18mm WBP ply between the joists, layer of green WR plasterboard over the top and finished with grant westfield multipanel: http://www.multipanel.co.uk/

If water gets to the ply that's sat in the joist past all this then its proper buggered.