Sagging Ornate Plaster Ceilings - Help!

[finchy]

We have a 90 year old house with ornate plaster ceilings that have seen better days.

There are a couple of problems that need fixing.

1. They sag - as much as 3 or 4cm in places. Most caused by gravity, not water. Some sections are made panels that are 2 foot wide and only supported on the edges - no cross battens at all. Some is nailed (and the nails are pulling out), some (but not much) is plastered over the battens. Much of it is dodgy, and I want to repair it before it gets any worse.

2. There are cracks through the thickness of the plaster - in trying to straighten the sagging, I am making them worse, and I accept that risk, but want to be able to finish it so that it both looks good and is structurally sound.

3. The paint (or whatever) that the plaster is finished with is flakey - I can remove a lot with nothing more than a paint scraper and a lot of patience - but some is quite sound. Because of the thickness, if I don't remove it all, whatever I put over it will look patchy (or am I being too fussy, and I will notice the fine detail once it's finished)

To repair the sagging I have experimented on one section by cleaning the dust and crap out of the ceiling space and laying a few lines of "Liquid Nails" then pushing the plaster back in place and holding it with props from below for 24 hours. Results so far have been excellent. Is there any reason why I shouldn't continue, or is there a better way of doing this?


Next Question - What's the best way to remove the remainder of the paint - it is quite thick in places, and I really don't want to damage the ornate cornice, rose etc etc......

Thirdly - What's the best product to fill the cracks? I have also come across someone who suggested placing hessian over the battens and swamping it with plaster - this, whilst it won't fix the cracks, will provide some structural integrity to the whole shebang. What do people think about this as an option.

Finally - I assume I need to finish with an oil based primer and a couple of coats of ceiling white. Any other suggestions?

Thanks in advance.....

[johnc]

Rod will eventually appear if you are in luck and answer your questions. I suspect the liquid nails will be a tempory fix only, the sheets you have pre date the later large sheets that were prepared on float style tables. I thought the standard size was 3' not 2' square. I would consider seeking out a plasterer that doesn't mind working with plasterglass sheets and getting a few tips about securing the loose sheets. The swamp with plaster method is probably the right advice which is along the lines of how the larger panels would have been fixed, basically hemp or sisal with plaster sloshed onto the matting.

[rod@plasterbrok]

good start John, I will elaborate a bit tomorrow when I have a bit more time. Thanks for your confidence.

Cheers

[felixe]

Rod, John and Finchy,

I am glad Finchy asked these questions, one of our ceilings is in the same state of (dis)repair, it has sagged slightly but of more concern is the flaking. It is on our "to do" list of repairs, so I am interested in any suggestions.
Finchy I would like it if you would post photos, maybe I should post some too, and we can compare?

Sorry didn't mean to push in or hijack the thread, but we were "literally" just sitting in the living room looking at another of our ceilings and taking note that it is starting to flake, and I was thinking I should search the forum - what timing!

Regards,

Felixe.

[rod@plasterbrok]

We had a big thread on this subject several months ago. I haven't had a chance to go back looking for it. But it would be worth a read.

The only reason the liquid nails idea would fail is that the bond is weakend by dust. Might be a good idea to dampen the sheet and joist if possible before applying the liquid nails to get a better bond.

The scrimming method you mentioned is also quite effective again you would need to dampen down to get a good bond. Scrimming is dipping sisal in a bucket of wet mix of cornice adhesive (or back blocking cement). Then laying it over the joist or batten onto the back of the sheet. You can add citric acid to your mix so it wont set so quick. A tea spoon into 1 bucket of mix.

Screwing or nailing from the front will not always work due to the weakness of the sheet and the pressure on them to return to the bowed state, will make the nails pop straight through.

Any operation to push the sheets back into place can result in more damage than when you started. The sheet surface will most likely crack.

If you manage to get it all back up flat and glued or scrimmed in place, scrape back all the loose flacky paint etc an skim coat the lot with cornice adhesive toped with top coat.

If you have an area that has saged between the battens you can prop it from underneath, until it is flat then cut strips of ceiling plaster board 300mm wide and the length is the distance between the battens. Then using a very wet mix of cornice adhesive glue two thicknesses of the strips (as ribs) between the battens and at 300mm centers. (see very quickly prepared diagarm) Next post!!

Some ceilings, sagging badly, just can't be saved. But if you are careful and take your time you should get a reasonable result compared to the cost to replace.

Hope this helps

[rod@plasterbrok]

here is the pic.