How safe are hairline cracks in a ceiling?

[NT0S]

I stripped back the ceiling paper in one of the rooms in our new house we are decorating, and the plaster is old lime & horsehair. The house is 1940s.

The ceiling is in good condition apart from a few hair line cracks. Obviously the plaster is old so I guess that's to be expected.


I was wondering how safe the plaster is expected to be if it has hair line cracks?

As I say it's in good condition apart from that, but we'd ideally like to paint over it now the paper is off.
I just don't know whether it's going to be a problem later in down the line.


Cheers.

LP18, Today at 9:33 PM Report#1Reply


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[morturn]

I would say that unless it is visibly bulging it should probably be fine. If you tap it and run your fingernails over it, you can lean to hear for any hollow spots.

All older houses have some movement that causes hairline cracks, just rake out the cracks and fill with a propriety decorator’s filler. Lots of people will suggest you cross line the ceiling with lining paper. Unless the condition of the ceiling is really poor, don’t bother. I stopped doing that years ago, just get a decent quality paint like Dulux Trade emulsion, and give it two good coats.

 

[AndyT]

You could go up into the loft (or lift the floorboards above) and look at how well the plaster is adhering to the wooden laths if you want to be sure.
On a sound ceiling you should see plaster squeezed up through the laths and still clinging firmly to them. On a failing ceiling you'll find a litter of little separate bits lying on top of the laths, with areas of plaster below not held up by much at all.
I think it's possible to reattach old plaster to the laths, using bonding plaster from above, but I've never done that - our older Victorian ceilings are still clinging on, despite the occasional hairline crack that just gets filled in when I redecorate.

If it's no good, another approach is to screw plasterboard to the joists over the existing ceiling and skim over. This avoids the filthy mess of pulling the old stuff down. I expect professional plasterers would recommend the latter.

Or you could repaper!

 

[Hot stuff]

The first flat I ever bought had lathe and plaster walls and ceilings and while we were decorating the living room prior to moving in a huge part of the bedroom ceiling came down, exactly where the bed would have been had it been a couple of weeks later.
I'm in the middle of renovating a rental house which has cracks and bulges in some of the ceilings so they're being sheeted over to prevent possible disasters. Years of door slamming, tramping up and down stairs and furniture shifting etc all contribute to loosening old plasters grip on lathes.
As Morturn says, go over any suspect areas and check for hollow sounds, now is the time to sort it out rather than when you're in and settled.

 

[Rorschach]

adding plasterboard can add a lot of load to an old ceiling so be careful.

 

[Lons]

All the ceilings in my sons 1890 house had loads of hairline cracks when he bought it 4 years ago although the plaster was reasonably sound I was concerned that over time it might loosen especially with a then new granddaughter who in a few years would be jumping up and down on the bedroom floors.

The joists in older houses are usually larger section and as long as in good condition are perfectly capable of carrying additional load so we screwed slaters laths along each joist through the existing plaster then fixed 12mm plasterboard screwed to the laths and skimmed over.
One of the reasons for the laths was to give a flat base for the new boards as we packed out the lathes slightly where necessary.

Maybe not a conventional approach but 4 years on it's still perfect, so far, despite the little girl practicing gymnastics upstairs. :roll:

Bob

 

[skipdiver]

I had the same thing and after due consideration, i prepped and filled, sanded down and lined them with 1200 gauge lining paper. Slapped on some emulsion and they still look good three years on.

 

[NT0S]

Thanks for all the great replies!

I've knocked on the plaster and it sounds solid to me; no hollows.

I also went to the loft and took a look at the ceiling above as suggested. It's very difficult to get a picture, so unfortunately this is the best I have.

I'm not sure whether you can tell anything about the ceiling from that, but you can see the plaster bulging through the laths.

I've also took a couple of pictures.
You have hairline ones like these that span quite a way:

as has been said, presumably just from the normal movement of the building.

Upon closer inspection, there is also this one which is a bit wider:

As I say, and as was suggested dependant on whether the ceiling was sound enough to do so, I was going to emulation over it once I'd filled the cracks.

I suppose the reason I'm most concerned is because one of the hairline cracks (first photo) is above where the bed is going. So I just envisage us settling into a newly decorated room, only to get a face full of grit and horsehair during the night! Haha




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[AndyT]

In your first picture, if the bits of plaster bulging up through the laths are still attached to the rest below them, and the laths are still attached to the joists, you're fine. A little filler and a coat of paint are all you need.

 

[NT0S]

In your first picture, if the bits of plaster bulging up through the laths are still attached to the rest below them, and the laths are still attached to the joists, you're fine. A little filler and a coat of paint are all you need.

Great, thanks for the reply.

So regarding the filler; do I widen the crack with a pen knife and then add it?



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[Phil Pascoe]

Make sure the ceiling timbers aren't carrying too much weight - in my Victorian house some clown had put the roof tank on the ceiling timbers - right in the centre of the room. :shock:

 

[NT0S]

Make sure the ceiling timbers aren't carrying too much weight - in my Victorian house some clown had put the roof tank on the ceiling timbers - right in the centre of the room. :shock:

Actually, there is a plastic tank similar to this one up there above the room.

Although it's not attached to anything and is empty.


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