Is a sagging ceiling dangerous? Could it collapse?

A sagging ceiling can be quite concerning. After all, there is a lot of weight in a ceiling and were it to fall through, it could result in serious damage and potential injury.

There are two parts of a ceiling that can sag. The first is the plaster and the second is the timber joists.

Either of these sagging can be cause for concern and both have the potential to be dangerous. If your joists are sagging, this could indicate a serious structural issue. This would need inspecting by a professional, such as a structural engineer.

If it is the plaster sagging, this is not a structural issue. However, it is still something you should fix sooner rather than later. A sagging plaster ceiling has the potential to be dangerous, as it could potentially fall through.

is a sagging ceiling 

Identifying and fixing a sagging plasterboard ceiling

One of the easiest ways to identify sagging plasterboard, is to simply try and push it back up. Usually the plaster will be sagging because fixings have pulled through with the weight of the plaster.

In a plasterboard ceiling, this could happen for several reasons including:

  • Water damage – If the ceiling has become damp in the past, due to a leak or some other exposure to moisture. This can deteriorate and soften the boards, causing the fixing to pull through with the weight.

  • Not enough or wrong fixings – There is a chance that when the boards were fitted, not enough fixings were applied. This extra weight could cause the board to pull through the fixings. It is also possible, that short screws were used, and the weight pulled these out of the timber.

  • The ceiling was fitted with clout nails – In the past, before drywall screws were used as standard, clout nails would have been used, these are much more prone to popping through the plaster.

If your plasterboards are damaged due to moisture, then you will probably need to replace them. However, if fixings have pulled through and the boards are in good condition. You should just be able to screw them back up.

To push your boards back up, you may need to use some kind of prop. A few options include:

  • Plasterboard props
  • A plasterboard lift
  • Acrow props and a plank of wood

You could even create a prop with some timber and use it to wedge the ceiling up. Whatever you use, the goal is to push the boards up tight to the joist. Once it is secure in place, you can re-fix with long drywall screws (38-50mm).

Sagging old lime plaster ceiling

If you have an old ceiling in your property, that is not plasterboard. It is likely constructed with lime plaster and thin strips of timber, a technique known as lath and plaster. This is how ceilings were plastered prior to plasterboards and modern plaster.

It is very common to see this type of ceiling sagging. The laths are usually fitted with clout nails and the lime plaster is skimmed over the top, so there are multiple points of failure.

I personally bought a property in around 2010 that had this exact issue. There was no problem with damp, so I decided to simply overboard with plasterboard.

Essentially, you have two options if a lath and plaster ceiling is sagging.

  1. Overboard – To do this, you would prop the board up under the old ceiling and push it back up to the joists, then fix with long drywall screws (75mm+).

  2. Pull the ceiling down – This is a horrendous job. The dust and mess that this creates is substantial. It is a very unpleasant job, and I would advise you avoid this unless completely necessary.

Just like sagging plasterboard, a sagging lime plaster ceiling can be dangerous. Therefore, you should fix it ASAP.   

Need help fixing a sagging plaster ceiling?

Obviously, propping a ceiling and fixing up plasterboard is not a job for everyone. It is heavy work and does require a little knowledge.

If you do need help to repair a sagging ceiling, the best person for the job is a plasterer. They can also skim the board when the job is finished.

To find a decent plasterer we recommend that you compare quotes. The best way to do this is via online comparison sites.

Doing it online can save a huge amount of time. Plus, you can read past customer reviews, and also the prices tend to be much cheaper than going direct.

To see how much it would cost to fix a sagging ceiling Click Here

What if the joists are sagging?

If you have ruled out sagging plaster, then it looks like the issue is with your timber joists. This is potentially a very serious issue, and you should seek the help of a structural engineer as soon as possible.

Potential reasons for joists sagging include:

  • Incorrect size joists. If the joists are too small for the span they are covering, this can cause sagging. Building regulations state that certain thickness and depth must be used over different spans.

    For example, a joist ceiling using 38mm x 122mm timbers, could only span around 2.2m before it needs support.

    However, 38mm x 220mm joists could span over 4m before needing support.

  • A load bearing wall was removed – This is a serious issue and needs addressing without delay. Removal of a structural wall can cause problems due to movement. In the worst-case scenario, it could result in structural collapse.

  • Damage to timbers – The most common causes, would be rot and insect infestation (woodworm). Either of these can seriously weaken timbers and cause a ceiling to sag.

Obviously, any of these can be quite dangerous, so if you think the sag in your ceiling is due to sagging joists, get a professional in a soon as you can.

Click here to find the best local structural surveyor


A sagging ceiling can definitely be dangerous. Whether the problem is with the plaster, or the timber joist, both come with their own unique issues.

With plaster, you may risk mess, damage, and even injury if the ceiling does fail. However, ceiling joist are more serious. These need fixing quickly. In the worst-case, structural collapse is a real possibility.