Nail pops in plasterboard: why they appear and how they are fixed before painting

Nail pops appear because the timber framing behind the plasterboard shrinks or moves, the board is pulled back towards the framing, and the nail head, which has not moved, ends up standing proud of the surface. The lasting repair is to refix the board with a new screw close to the popped nail, reset or remove the old fastener, then re-stop and repaint, rather than just filling over the bump.

They show up as small round bumps or cracked discs of filler in a regular line, usually on ceilings and along the line of a stud or joist. They are one of the most common things a painter finds on a GIB ceiling, and they are almost always cosmetic. Our guide to GIB stopping in Wellington covers the wider stopping process; this article covers pops only.

Why do nail pops happen?

The manufacturer of GIB plasterboard lists four causes in its best practice bulletins on fastener popping:

• Substrate movement. Timber framing moves and shrinks with changes in temperature and moisture. This is the big one.
• Incorrect fasteners. Overly long fasteners are one contributing factor, which is why the right type and length matters for each lining system.
• Framing not aligned. Bent, twisted or warped framing, or nail plates and hold-down ties not set flush, leave the board loosely attached.
• Incorrect installation. Skewed or overdriven fixings that break the face paper leave a weak point for movement.

The shrinkage mechanism is worth understanding because it explains why filling alone fails. GIB's bulletin explains that timber dries from the outside in. The tip of a nail sits deep in timber that has not dried yet, so the nail stays put. The outer face of the framing shrinks back, and the board glued or fixed to it moves inwards with it. The board moves, the nail head does not, and the head ends up proud of the surface.

The same bulletin notes that a 5% moisture change can result in a 1mm dimensional movement in timber. That is more than enough to push a nail head through a thin skin of stopping compound.

Why are they worse in new or renovated houses?

Because that is when the framing is still drying out. GIB's bulletin states that its site guide requires timber framing to be at 18% moisture content or less at the time of lining, and the manufacturer recommends 12% or less where heat pumps or central heating will be installed, because the timber can dry much further once the heating runs. Framing that was lined wet, or a house that has just had a heat pump fitted, will pop more.

That is also why GIB recommends waiting. Its repair bulletin says popping that appears after at least one month's heating cycle is likely caused by timber shrinkage, and advises not repairing until the end of a full heating cycle, because more shrinkage is likely and the pops will return. Once the timber has been through a full heating cycle, it has probably reached equilibrium and stabilised, and seasonal changes are unlikely to cause further pops.

In an older house, a sudden rash of pops after years of nothing is worth a second look. A new heat pump or insulation can do it. So can a leak wetting the framing, or ground movement after an earthquake. If pops come with cracked cornices or diagonal cracks from door corners, see our article on ceiling cracks after a quake before anyone paints.

Why doesn't just filling the pop work?

Because the board is still loose. Sanding the nail head flush and skimming over it hides the bump for a while, but the gap between the board and the framing is still there. Any pressure on the ceiling, such as someone walking in the roof space, a door slamming or the next season of movement, pushes the board and the nail head reappears through the filler, usually as a neat cracked circle.

Approach	What it involves	Likely result
Fill over the bump	Sand the head flush, skim, spot paint	Looks fine for a while, often returns in the same place
Punch the nail only	Drive the old head deeper, fill	Better, but the board may still be loose against the framing
Refix and re-stop	New screw beside the pop with the board pressed tight, reset the old head, re-stop in coats	The accepted repair; lasts once the framing has stabilised

How is a nail pop fixed properly?

GIB's repair bulletin covers the core of it: the new screw, firm pressure, removing loose material and the coats of compound. The full sequence on a painted ceiling looks like this:

1. Wait until the framing has been through a full heating cycle if the house is new or newly heated.
2. Drive a new screw 50mm from the popped fastener while pushing the board firmly against the framing, so the board is pulled tight to the timber.
3. Deal with the old fastener, either setting it back below the surface or removing it, so there is nothing left proud.
4. Remove loose compound and face paper around the repair.
5. Apply two coats of taping compound followed by a topping coat, sanding between coats.
6. Seal and repaint.

The painting part is where the repair either disappears or shows. A spot of fresh stopping compound absorbs paint differently from the surrounding ceiling, so each repair needs sealing, and on a ceiling that is more than a few years old, the whole ceiling usually needs a full coat. Otherwise every repair shows as a slightly different sheen in raking light from a window.

Can you fix nail pops yourself?

A handful of pops on a single-storey ceiling is a reasonable DIY job if you are comfortable on a ladder and with a sanding block. You need a drill, plasterboard screws of the right length, a broad knife, taping compound, topping compound and ceiling paint. The hard part is not the fixing; it is feathering the compound out wide enough that the patch cannot be seen.

Two things to check first. Homes painted before the 1980s may contain lead-based paint, and older ceilings have often been painted many times, so have the paint tested before sanding it. And if the ceiling is old lath and plaster or a textured finish rather than plasterboard, this repair does not apply; that is a different job.

When should a professional do it?

When there are dozens of pops across several rooms, when the ceiling needs repainting anyway, or when the pops sit alongside cracks. At that point it is more efficient to refix everything in one pass, stop to a consistent level and paint the ceilings in one go. It is routine work for our plastering and GIB stopping team.

If you have popped nails and are not sure whether it is movement, a leak or just time, ask us to take a look and we will tell you what needs fixing before it gets painted.