A lot of the calls we take on the Gold Coast start with someone asking for a quote on a new ceiling because the plasterboard has started to droop. Fair enough. A sagging ceiling looks bad and feels unsafe, but it doesn’t always need replacing. Caught early, the sheets can often be fixed back up to the frame for far less than a new ceiling costs.
Here’s how to spot the problem, what causes it and the repair options.
Warning Signs of a Sagging Ceiling
The tricky part is that a plasterboard ceiling can be pulling away for a long time before you notice. The WA Building Commission’s 2017 industry bulletin on plasterboard ceiling failures says there are generally little to no warning signs a homeowner will easily notice before a ceiling fails. So it pays to look up now and then.
Things to look for:
- Cracks along the cornice: fine cracking where the ceiling meets the wall, or a gap opening up behind the cornice.
- A dip or bow in the ceiling: easiest to see when morning or late afternoon light runs across it.
- Popped screws or nails: small round bumps in the paint, in rows along the frame lines.
- Water stains or soft patches: brown rings or bubbled paint usually mean water has been sitting on the plasterboard from above.
A simple check for an early sag is to press the area up gently with your hand or the end of a broom. If the plasterboard moves up and then drops back, it has come away from the ceiling joists or battens. Don’t push hard on a big bulge or anywhere that looks wet, though (that’s the time to step back and call a plasterer). And if your home was built before 1990, skip this check and read the asbestos section below first.
A building inspector can check the roof framing, but nobody can see from below whether the glue was put on properly. The bulletin notes that once the sheets are installed, it’s very difficult to judge how well the fixings will hold long term.
What Causes Plasterboard Ceilings to Sag
Plasterboard ceilings are held up by adhesive plus screws or nails into the timber frame. A ceiling sags when some of that grip is lost, usually for one of these reasons:
- Poor original installation: the WA Building Commission inspected homes where large areas of ceiling had collapsed, and the one constant factor in every case was poor application of adhesive.
- Moisture in the roof space: the same bulletin lists sagging ceilings, popped nails and rotting framing among the effects of high moisture in the roof. Exhaust fans that vent into the roof space are one source the bulletin names. A roof leak after a storm can do the same.
- Too much weight on the sheets: plasterboard manufacturers set limits on how much insulation can sit directly on the board, and the bulletin says ducting should be supported clear of the ceiling and heavy fittings like ceiling fans fixed to the frame, not the plasterboard. We’ve also seen a carpet python resting on the sheets add enough weight to start a sag.
- Movement in the frame: the bulletin notes that poor connections between the joists and wall plates can let the frame move later on. Ongoing vibration from nearby building work can also loosen fixings over time.
- Termite damage: if termites have been in the ceiling timbers, the frame itself is weaker, and a pest controller needs to treat them before any repair.
Why a Sagging Ceiling Gets Worse Over Time
Plasterboard is heavier than it looks. On a wall the weight is spread down through the frame, but a ceiling sheet hangs from its glue and fixings. Add the insulation on top and years of roof dust, and every screw is carrying a fair load.
Once one section lets go, the rest of the sheet takes up the slack. The bulletin puts it plainly: when a ceiling loses one or two fixing points, the remaining fixings carry load they weren’t designed for, and that can lead to ceiling failure. That’s why we’d rather see a small dip early than a big one later.
If the bulge is large, growing or wet, keep people (and beds) out from under it until it has been looked at.
Sagging Ceiling Repair Options
Which repair suits your home depends on how big the sagging area is, how long it has been bowing and what caused it.
Re-fixing a Small Section of Sagging Ceiling
If the sag is caught early and the sheet hasn’t bowed out of shape, new screws can pull the plasterboard back up against the battens and hold it there. The screw heads are then set, sanded and painted. This is usually the quickest and cheapest sagging ceiling repair.
Propping and Re-gluing a Larger Sagging Ceiling
When new screws won’t hold on their own, the sheets need to be pushed back flat and held in place with props while adhesive is applied from the roof side and extra screws go in from below. The props stay up until the adhesive sets, so the room is out of action for a while. On a big area, replacement sometimes works out simpler.
Replacing the Plasterboard Ceiling
A sheet that has been hanging down for a long time takes on a permanent bow, and water-damaged plasterboard goes soft. Neither can be pushed back flat. In that case the old sheets and cornice come down, the framing is checked and any bowed or damaged timber is fixed, then new sheets and cornice go up. New ceilings should be installed to the plasterboard maker’s instructions and AS/NZS 2589, the Australian standard for fixing and finishing plasterboard linings that the bulletin refers to.
Building a New Ceiling Below the Old One
If your ceilings are high, there’s another option. The old ceiling stays where it is and a new ceiling is framed and lined just below it. You skip the mess of pulling the old ceiling down and the insulation stays put. The trade-off is a lower ceiling, so it only suits rooms with height to spare.
Ceiling Repairs in Older Homes: Check for Asbestos First
If your Gold Coast home was built before 1990, check before anyone touches the ceiling. The QBCC’s asbestos safety guide says a house built before 1990 has a good chance of containing some asbestos, and some homes built in the 1990s and early 2000s still used asbestos products until the total ban in 2003. You can’t tell by looking. Only a lab test confirms it.
So in an older home, don’t cut, drill or pull at a sagging ceiling yourself, and mention the age of the house when you call.
Should You Repair or Replace a Sagging Ceiling?
It comes down to a few things:
- Size: a small section can usually be re-fixed, while a whole room that has dropped often needs new sheets.
- Shape: if the plasterboard can be pushed back flat, a repair is possible. If it has bowed for good, it can’t.
- Water: wet or stained plasterboard is usually replaced, and the leak has to be fixed first.
- Cause: if the cause isn’t fixed, the new ceiling can go the same way. A roof leak needs a roofer and termites need a pest controller before the plastering starts.
Sagging Ceiling Repairs on the Gold Coast
Gold Coast Plastering has more than 25 years of plastering experience and repairs and replaces ceilings in homes across the Gold Coast. If you’ve noticed a dip, a crack along the cornice or a water stain, call (07) 5315 8349 or request a free quote. Tell us what you’ve noticed and in which room, and we’ll explain whether a repair will hold or new sheets are the better value. You’ll find more on our residential plastering and renovations and restorations pages.
Gold Coast Plastering: MGH Contracting Pty Ltd, QBCC Licence 15576119, and All Paintworx Pty Ltd, QBCC Licence 15511709. You can check both on the QBCC licensee register.
