Plasterboard is the material most likely to be ruined before anyone gets around to deciding what to do with it. It arrives in packs, it gets ordered by the pack, and whatever's left leans against a wall in the garage until the corners are soft and the paper's furred up along one edge.
At that point it's genuinely rubbish. Before that point it's worth real money, because a full sheet costs what it costs and someone doing a small job would much rather pay you than a merchant.
The difference between those two outcomes is mostly about the first week.
Store it flat or lose it
This is the whole trick and almost nobody does it.
Plasterboard leaned against a wall will bow, and once it has a bow through it, it will never sit flat on a stud again. Stand it in a garage through a humid fortnight and the paper face lifts along the bottom edge where it's touching concrete.
If there's any chance you're keeping it: lay it flat, off the slab, on a couple of lengths of timber. Keep it dry and out of direct sun. Done that way it's still sellable in six months. Leaned in the corner, it's landfill in three weeks.
What's worth keeping versus moving on
Full sheets are worth selling every time. Someone is always doing a single-room job, a garage conversion or a patch-up, and buying one sheet retail means either paying delivery or borrowing a ute.
Half sheets and big offcuts, say anything over a metre square, still have buyers. Handy for cupboard linings, small patches and shed jobs.
Small offcuts aren't worth listing and aren't worth storing either. If they're clean, some community workshops and men's sheds will take them. Otherwise they're the honest bit of the load that genuinely belongs in the bin.
Specialty board is the sleeper. Wet-area sheeting, fire-rated, acoustic and impact-resistant board all cost noticeably more than standard, and people doing bathrooms, home theatres and garage conversions actively hunt for them second-hand. If your leftovers are anything other than standard, say so in the listing. It's the difference between a slow sell and a same-day pickup.
Be honest about condition, it sells faster
Nobody expects second-hand plasterboard to be perfect. What they need to know is whether they can use it.
Say plainly whether the edges are intact, whether it's been stored flat, and whether it's been anywhere damp. Photograph the stack, one long edge, and any damage. A listing that admits a dinged corner sells quicker than one that hides it, because the buyer doesn't waste a trip and you don't waste an afternoon.
Mention the size and thickness. It matters more than people think, and 6mm, 10mm and 13mm all have different jobs.
Where to move it
The problem with the general classifieds is that plasterboard doesn't photograph well and doesn't compete for attention against furniture. It's a boring, functional product that only makes sense to someone who already knows they need it.
That's why Overrun exists. It's an Australian marketplace for building materials and nothing else, so everyone on it is a tradie, builder or renovator who is specifically looking for the sort of thing you're holding. Listing takes under a minute from your phone, the buyer comes and collects, and they pay you directly. We never take a cut.
My husband is on the tools and this was one of the things he complained about most.. not that leftover sheets were worthless, but that there was no quick way to turn them into anything.
The realistic outcome
Half a pack of standard sheets plus a few wet-area boards is a genuinely useful amount of money back on a job, and it's ten minutes of your time. More to the point, it's ten minutes now instead of a tip run later, because that's where it ends up otherwise.
Plasterboard is heavy, and tip fees are usually charged by weight.
Quick answers
Can you sell leftover plasterboard? Yes, particularly full sheets and specialty board like wet-area, fire-rated or acoustic. Condition matters more than age, so how it was stored is the main thing buyers ask about.
How should leftover plasterboard be stored? Flat, raised off the floor on timber, dry and out of the sun. Leaning it against a wall will bow it, and a bowed sheet will not sit flat on a stud again.
Are plasterboard offcuts worth anything? Anything over about a metre square still has buyers for patching and cupboard linings. Smaller pieces are usually best given to a community workshop or binned.