Repairing cellular core wall

[BishBashBosh]

Hi,
My first post, so be gentle with me!

I have removed the old tiles from my shower room. A fair proportion of the plasterboard is too far gone to tile onto (couldn't avoid damaging it). I plan to replace it (probably with marmox board), but my problem is the wall is constructed from "cellular core" wallboards (a sandwich of two sheets of 12.5mm plasterboard with cardboard honeycomb core).
- I don't want to affect the room on the other side (bathroom, half-tiled)
- If I remove one side, and the core, will it weaken the other side too much? I think it's the core that gives it its rigidity.
- Studs are 900mm apart, I think I will need them at 600mm max for marmox?

Here's my plan. Feel free to pull it to bits if you think it's no good.
- Cut vertical slots in damaged board, half-way between existing studs (i.e. every 450mm).
- Fit new studs in slots, stick to 'other' board with panel adhesive, screwed to sole and head plates.
- Do the same for horizontal noggins (300mm centres, according to marmox site - seems a bit excessive?)
- When adhesive has set, remove the remaining plasterboard and core.
- Screw on the marmox board, and tile.

What should I use for the new studs? Existing studs are only 38mm thickness. I don't want to use thicker, because I would have a step (it's only half a wall that's damaged). 38mm timber isn't going to give much rigidity, e.g. for hanging shower screen on. Can you get metal studs that thin? Or should I make them out of strips of ply?

I haven't chosen the tiles yet, but they won't be particulary heavy (not stone).

Thanks
BBB

[whitebeam]

Yes if you remove the core it will weaken the one board remaining and there a good chance you may damage the half tiled bathroom, You say your've removed a fair amount of the existing water damaged board, How much. If your talking metal partition the minimum is 50mm, If your going to fit battens within the core they need to be screwed from the other side because of the shower door your going to fit.

[BishBashBosh]

Thanks whitebeam. Its not water damage, it is damage caused when removing old tiles. Previously tiled area is 800x800mm shower cubicle. There are about 4 areas of damage, largest is 300x700mm in top corner, where it is almost completely destroyed; others are about half that size. I was hoping the panel adhesive would fix it adequately to 'far side' board, to avoid damaging tiles on other side.

Click here for a pic of the worst damage.

[whitebeam]

Personally I would square off where damage has accured, Cut out straight lines with a pad saw or stanley knife get some 12.5mm plasterboard cut to hole sizes Mix up some dri wall adhesive and dab some within the holes so it sits slightly proud of the existing surface and bed new cut board onto the addy and make sure it's flush with your existing boards. Hope this helps.