6 minute read -
Sanding Walls with a Drywall Sander: The Right Approach for Each Wall
For sanding whole walls and ceilings, a drywall sander is the most practical choice: a round, tilting sanding head on a long pole, connected to a dust extractor. For a small wall or a few filled patches, a sheet sander with mesh abrasive is enough.
Whether sanding makes sense at all depends on the wall. Plasterboard and filled walls only need a light sand, but old textured plaster or textured coatings such as Artex should never be sanded until you know what is in them.
What will you learn in this article?
- What is a drywall sander?
- Which sander suits which wall?
- Plasterboard and filled walls
- Coarse textured plaster
- Textured paint
- Glass fibre wallcovering
- Preparing a wall for sanding
- How to sand a wall
- Keeping dust down
- Safety
- Common mistakes
- Frequently asked questions about sanding walls
- In short: sanding walls with a drywall sander
What is a drywall sander?
A drywall sander, often called a giraffe sander or long-reach sander, has a motor with a round sanding disc at the end of a pole of around one and a half metres or longer. The head pivots so the disc stays flat against the wall. Dust is drawn through the pole to a dust extractor. That lets you sand large areas and ceilings without scaffolding and with far less dust in the room.
Which sander suits which wall?
| Wall | Sand it? | Machine | Grit |
|---|---|---|---|
| Plasterboard with filled joints | Yes, lightly | Drywall sander or sheet sander | 120 to 180 |
| Filled or plastered wall with imperfections | Yes | Drywall sander | 120 to 150 |
| Painted wall you are repainting | Light key only | Sheet sander or drywall sander | 150 to 180 |
| Textured plaster or render finish | Only knock off the peaks, after testing | Drywall sander | 40 to 80 |
| Textured paint or coating | Preferably not, depending on age | See below | See below |
| Glass fibre wallcovering | No, only remove paint drips | By hand | 180 to 240 |
Plasterboard and filled walls
This is the most common wall-sanding job. After filling, you sand the joints and holes flush so they do not show through the paint. Use mesh abrasive of 120 to 180 grit with light pressure, because you do not want to damage the paper face of the plasterboard. A drywall sander is quick and even here. For a few joints you can also use a sheet sander, for example a cordless sander from the Maxxpack 18V range.
Coarse textured plaster
If you want to have a wall with a heavy textured finish skimmed smooth, you can first knock off the sharp peaks with a coarse grit. That means less filler or plaster is needed. Sanding it completely flat will not work: the texture is too deep. For that you need a plasterer to apply a new skim coat.
Textured paint
Textured paint is a thick paint with grit mixed into it. Sanding will not make the wall truly smooth and creates a lot of dust. Older textured paint carries the same warning as textured plaster: have it tested for asbestos first. If it is asbestos-free, you can knock off the peaks with a coarse grit and then fill the wall smooth or have it skimmed.
Glass fibre wallcovering
Do not sand glass fibre wallcovering. You will damage the weave and release fine glass fibres that cause itching and irritation. If you want a new colour, clean the wallcovering and paint over it. Remove drips or paint residue carefully by hand with fine 180 to 240 grit sandpaper. If you want a smooth wall, strip the wallcovering and fill the wall again.
Preparing a wall for sanding
- Move furniture out or cover it with dust sheets or plastic.
- Tape over sockets and switches, and if in doubt switch off the circuit at the consumer unit.
- Seal doorways with dust screens or plastic sheeting.
- Check that the wall is dry and remove loose paint or loose plaster with a filling knife.
- Connect the drywall sander to a dust extractor.
How to sand a wall
Switch the machine on before the disc touches the wall. Place the head flat against the wall and move it in steady, overlapping passes, for example from top to bottom. Do not press: the weight of the head and light pressure are enough. Keep the sander moving, or you will sand a dip.
Check the result with a work light held at a low angle to the wall. That shows up imperfections you would otherwise only notice once the paint is on.
Keeping dust down
Wall dust is fine and spreads through the whole house. Always connect the drywall sander to a dust extractor with a fine dust filter. An ordinary household vacuum cleaner clogs quickly and can overheat. Open a window, but not in a way that blows dust into other rooms.
Safety
Wear a dust mask with at least a P2 filter, close-fitting safety goggles when sanding ceilings and ear defenders for longer jobs. Work from a stable stepladder or a mobile scaffold tower. Do not sand old materials unless you are sure they are asbestos-free.
Common mistakes
- Using a drywall sander without a dust extractor.
- Pressing too hard, so the head judders and gouges.
- Sanding old textured plaster or Artex without an asbestos test.
- Trying to sand glass fibre wallcovering smooth.
- Painting without removing the dust from the wall.
Frequently asked questions about sanding walls
Can I sand a wall with a random orbit sander?
For a small area, yes, with fine mesh abrasive and light pressure. For whole walls and ceilings it is hard work and creates a lot of dust. A drywall sander with extraction is quicker and cleaner.
Which grit should I use on a wall?
For filler and plasterboard, 120 to 180 grit. For knocking the peaks off coarse textured plaster, a coarse 40 to 80 grit, but only if the material is asbestos-free.
Do I need to sand a wall before painting?
On a smooth, clean wall in good condition it is usually not necessary. Do sand if there are filled patches, paint drips or imperfections. Give an old glossy paint finish a light key so the new paint adheres better.
Do I need a dust extractor?
With a drywall sander, yes. Without extraction so much fine dust is released that you can barely see and the whole house ends up covered. A dust extractor is built for fine dust and has a filter that holds on to it.
In short: sanding walls with a drywall sander
A drywall sander with a dust extractor is the quickest and cleanest way to sand plasterboard, filled walls and ceilings with 120 to 180 grit. Only knock the peaks off textured plaster, leave glass fibre wallcovering alone and never sand old textured coatings until they have been tested for asbestos.