Ceiling sagging

[DIY67]

There is a small area on our ceiling that is sagging (forgive the crude temp patch) as the old lime plaster has clearly lost it's grip on the old wooden slats. Probably because of the accidental foot treading in the loft on that spot by myself years ago. I understand to do it would take a patching job with plasterboard, but I really want to repair it as good as I can as the rest of the ceiling is sound. I have a a theory that if I injected some kind of hardener, glue or paste into a few spots the area and then propped it up from underneath until set, that would hold it.

If anyone can suggest a substance that would work I would be grateful.

Cheers.

 

[blup]

Strip the wall paper, remove loose or crumbly plaster and apply repair plaster.

Blup

 

[DIY67]

Ok, thanks. I was hoping to keep the paper but I could cut a neat patch around it out. The only trouble is I would have to re paper the whole ceiling as I don't have that paper to replace it. The paper does feel slightly damp though as the loft is quite high in humidity (especially as I have installed lap vents as the outside air is currently damp due to rain)

The patching plaster I could buy, but before I order some, I do have a half bag of plaster left over from a job I had done last year. Would that not do it ?

 

[blup]

You can hide overlapping wall paper quite effectively by cutting a curved pattern, the eye doesn’t see it provided it’s more or less the same. Worth a try with the spare plaster.

Blup

 

[cdbe]

Prop from below, hoover out in loft and pour sloppy bonding plaster on.

 

[DIY67]

I have half a bag of finishing plaster left, could that do it ?

 

[cdbe]

Yes.

 

[Wayners]

I think plaster needs to be removed.
If you try and prop up it will crumble away and fall.

 

[DIY67]

You mean the old plaster ? Do you still agree that pouring sloppy plaster will work ?

 

[RrogerD]

Are the lathes still in place and secure or have they sagged as well?

If it's just the plaster then, using a masonry drill, drill holes at intervals where the lathes are; vac out; inject first with diluted pva (to remove any dust, provide a key and help solidify the loose plaster) then, inject with white gripfill or similar. Hold everything in place until set using small 'plates' screwed into the lathes. Once set, remove plates, clean up and paint.

If the lathes themselves have sagged then you'll need to secure these first before doing the above.

Within the loft, clean the area of crumbling plaster etc; add 3x2 battens between the joists, level to the correct level of the ceiling. If it's a wide area then perhaps use a wide piece of 12mm ply and then the battens.

Follow the process above but use longer screws so as to affix into the ply above and not just the lathes.

 

[cdbe]

Worked for me, the plaster had "blown" off the lathe and was sagging but still largely intact, pushed back up nicely and looked good as new with a fill and paint.

 

[Notch7]

I think youtube channel on the trowel showed a way to do this recently, I think he uses plasterboard adhesive from above whilst wedging a board from below.

 

[DIY67]

Well it's got worse so have had to patch temp with another piece of card as can't face it before the new year.

 

[RrogerD]

Well it's got worse so have had to patch temp with another piece of card as can't face it before the new year.

Yeah that should hold it. Lol!!

 

[DIY67]

Better than nothing. I might use pva glue too.