Which sandpaper grit for plasterboard and filler?
Which sandpaper grit for plasterboard and filler?
120 to 150 grit to level joint compound and 220 for the final pass, ideally on a mesh with a vacuum attached.
The commonest fault in this job is not the grit but the pressure: joint compound is much softer than the board's paper facing, so bearing down on a proud joint cuts through the paper, raising a fuzz of fibres that swells when painted and shows as a rough halo around the joint. That damage cannot be sanded out — it has to be sealed and skimmed. Better to apply thinner coats and sand less. Dust is the other issue. Gypsum dust is extremely fine, travels through a house and irritates airways, and some joint compounds have contained crystalline silica, so a mask and extraction are worth using even though the material feels innocuous.
The options, ranked
| Option | Good at | Bad at |
|---|---|---|
| 120-150 grit | Cuts dried joint compound quickly without scoring it into ridges. | Will cut through the paper facing of the board if you press on a high spot. |
| 220 grit | The finishing pass that removes the previous scratches so the paint does not telegraph them. | Too fine to level anything. |
| Abrasive mesh with dust extraction | Does not clog, and the vacuum takes most of the dust before it reaches the room. | Needs a vacuum and a compatible sanding head. |
| Damp sponge sanding | Almost no airborne dust, and gentle on the paper facing. | Slower and it can soften and smear the compound if it is too wet. |
Technique that changes the outcome
- Apply thin coats and feather them wide so there is little to sand
- Use a light touch and a flat block or pole sander to avoid dishing the joint
- Check with a light held flat against the wall — raking light reveals every ridge
- Prime before painting: bare compound absorbs paint far faster than board paper and flashes differently
What goes wrong
- Sanding through to the board's paper facing
- Sanding without a mask or extraction; gypsum dust gets everywhere and irritates the airways
- Painting straight over sanded compound without primer
Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.
Other sandpaper grit questions
| For | Use |
|---|---|
| Bare wood | 80 to 120 to 150 on softwood, finishing at 180 or 220 on hardwood — and stop there, because over-sanding ruins stain. |
| Stripping paint | 40 to 80 grit open-coat aluminium oxide or ceramic — but test for lead paint before sanding anything painted before the 1990s. |
| Rusty metal | 60 to 80 grit to strip scale, 120 to 180 to blend — then prime the same day, because bare steel flash rusts within hours. |
| Between coats | 220 to 320 grit with almost no pressure — you are knocking off dust nibs, not removing the coat. |
| Plastic | Start at 320-600 wet for scratches, work up to 2000, then finish with a plastic polish — and keep it cool. |
| Car body filler | 80 grit to shape, 180 to refine, 320 before primer and 400-600 on the primer before paint. |
| Final finish | 400 to 600 dry, or 800 to 2000 wet on a fully cured film, followed by a polishing compound. |
| Wet sanding | Silicon carbide wet-or-dry paper, water with a drop of detergent, a rigid block, and 800 grit upwards. |
Common questions
- Which sandpaper grit for plasterboard and filler?
- 120 to 150 grit to level joint compound and 220 for the final pass, ideally on a mesh with a vacuum attached.
- What should I avoid?
- Sanding through to the board's paper facing Sanding without a mask or extraction; gypsum dust gets everywhere and irritates the airways Painting straight over sanded compound without primer
Related pages
- Which sandpaper grit for bare wood before finishing? 80 to 120 to 150 on softwood, finishing at 180 or 220 on hardwood — and stop there, because over-sanding ruins stain.
- Which sandpaper grit removes paint? 40 to 80 grit open-coat aluminium oxide or ceramic — but test for lead paint before sanding anything painted before the 1990s.
- Which sandpaper grit removes rust? 60 to 80 grit to strip scale, 120 to 180 to blend — then prime the same day, because bare steel flash rusts within hours.
- Which sandpaper grit between coats of paint or varnish? 220 to 320 grit with almost no pressure — you are knocking off dust nibs, not removing the coat.
- Which sandpaper grit for plastic? Start at 320-600 wet for scratches, work up to 2000, then finish with a plastic polish — and keep it cool.
- Which sandpaper grit for car body filler? 80 grit to shape, 180 to refine, 320 before primer and 400-600 on the primer before paint.
- Which sandpaper grit for a final finish? 400 to 600 dry, or 800 to 2000 wet on a fully cured film, followed by a polishing compound.
- Which sandpaper should I use for wet sanding? Silicon carbide wet-or-dry paper, water with a drop of detergent, a rigid block, and 800 grit upwards.
Sources
- Typical range compiled from manufacturer specifications — At One Place