How to deal with wet plasterboard?

[Keitai]

‘Mate who wants a quick solution. Baton and cladding?’

Batoning and cladding isn’t a ‘quick solution’ it is a cowboy way to go about it. There is clearly water ingress coming from outside so it’s either faulty guttering, outlet, pointing, flashing, window seals or a roof problem.

He knows but no one's going to do anything about it and building will be knocked down anyhow

 

[Keitai]

I agree that you need to fix the problem first. However, if that's not going to happen, here's an idea: affix a wall-mounted radiator / towel-rail / heater to that section of the wall and run it 24/7. It will dry out the damp plasterboard.
Sure, it's going to steadily rotting-away behind but at least it won't show in the room.
Be aware though that that water has to go somewhere as it dries and so also, a dehumidifier needed.
Edit: be mindful of the close-proximity of the curtain. It could overheat any heater placed nearby.

Plug in heater?

 

[cdbe]

Remove rad and skirting, get some of the least "bathroom like" t&g pvc panels, glue them on with no nails, seal the joint at the floor the best you can with silicone and refit the skirting. Should buy a bit of time.

 

[Keitai]

Remove rad and skirting, get some of the least "bathroom like" t&g pvc panels, glue them on with no nails, seal the joint at the floor the best you can with silicone and refit the skirting. Should buy a bit of time.

Have to remove rad? It's only wet to right of window. Would that work just to right of window? Going over lining paper too. Baton and screw?

 

[freddiemercurystwin]

When decorating the living room I found some foil faced bitumen type lining paper, behind this the wall was clearly damp, though you would never know from the hideous woodchip on the front which is bone dry. I left it well alone for another day, a Pandora's box there! Anyway point is I think it was this stuff: https://www.screwfix.com/p/wallrock...916G9VA-JOawDWkRLWBoCrdoQAvD_BwE&gclsrc=aw.ds or an earlier version, it's certainly masking the damp effectively and obviously a bodge but might be suitable here, you apply it with the adhesive: https://www.toolstation.com/wallroc...EJ9HXuM70sLuQM-qyexoCj1AQAvD_BwE&gclsrc=aw.ds and would then wallpaper over it as normal.

 

[Keitai]

When decorating the living room I found some foil faced bitumen type lining paper, behind this the wall was clearly damp, though you would never know from the hideous woodchip on the front which is bone dry. I left it well alone for another day, a Pandora's box there! Anyway point is I think it was this stuff: https://www.screwfix.com/p/wallrock...916G9VA-JOawDWkRLWBoCrdoQAvD_BwE&gclsrc=aw.ds or an earlier version, it's certainly masking the damp effectively and obviously a bodge but might be suitable here, you apply it with the adhesive: https://www.toolstation.com/wallroc...EJ9HXuM70sLuQM-qyexoCj1AQAvD_BwE&gclsrc=aw.ds and would then wallpaper over it as normal.

That looks awesome. Do you think I could get away with applying it just to the area to the right of the window and make it look normal?That's where the majority of damp is. Tiny bit of damp on wall next to it where lining paper is coming off

 

[cdbe]

Patching bits may work, but it's likely to come round the edges, if the source is ongoing and increasing neglect of the building fabric elsewhere then it's a big gamble - once it's let your landlord friend will have lots of legal obligations to the tenant, eg hotel accommodation if it becomes uninhabitable.

 

[RrogerD]

When decorating the living room I found some foil faced bitumen type lining paper, behind this the wall was clearly damp, though you would never know from the hideous woodchip on the front which is bone dry. I left it well alone for another day, a Pandora's box there! Anyway point is I think it was this stuff: https://www.screwfix.com/p/wallrock...916G9VA-JOawDWkRLWBoCrdoQAvD_BwE&gclsrc=aw.ds or an earlier version, it's certainly masking the damp effectively and obviously a bodge but might be suitable here, you apply it with the adhesive: https://www.toolstation.com/wallroc...EJ9HXuM70sLuQM-qyexoCj1AQAvD_BwE&gclsrc=aw.ds and would then wallpaper over it as normal.

Looking at this as an option is there any reason why one could not just instead, use SBR solution instead and then paper over?
Or is it that the bituminous paper has thermal properties as well as waterproof?