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Sanding a Wooden Floor: How to Restore Floorboards Step by Step
To sand wooden floorboards, use a drum or belt floor sander for the main area and an edging sander or detail sander for the edges and corners. Always work along the grain, following the length of the boards, and move from coarse to fine grit: for example 40, then 80, then 120.
Before you start sanding wooden floorboards, punch every nail head below the surface. A protruding nail will tear the sanding belt in seconds and can damage the machine.
What will you learn in this article?
- Which wooden floors can you sand?
- Which sander should you use?
- Preparation: nails, screws and gaps
- How to sand a wooden floor step by step
- How do you avoid scratches and dips?
- Finishing with varnish, oil or stain
- Safety
- Common mistakes
- Frequently asked questions about sanding wooden floors
- In short: sanding wooden floorboards
Which wooden floors can you sand?
Solid timber boards can be sanded several times. That includes old pine floorboards hiding under a carpet, solid oak boards and floors made from scaffold boards. Engineered boards with a thin real-wood top layer can only be sanded a limited number of times, so check how thick the wear layer is before you start. Laminate and vinyl cannot be sanded at all.
If you have parquet laid in a pattern such as herringbone, the order of work is different from a plank floor, so treat it as a separate job.
Which sander should you use?
| Machine | What it does on a wooden floor |
|---|---|
| Drum or belt floor sander | The whole floor area, removing old varnish and dirt |
| Edging sander | The strip along the walls the big machine cannot reach |
| Detail sander | Corners, around pipes, under radiators |
| Random orbit sander | Small floors, final sanding, sanding between coats |
| Belt sander | Single boards, thresholds, steps |
Floor sanders and edging sanders are widely available from tool hire shops. For a small area such as a landing or a loft floor, a random orbit sander will do the job, but expect it to take a lot longer. A cordless random orbit sander from the Maxxpack 18V range is handy for edges and final sanding, because there is no cable trailing across the floor.
A drywall sander with a telescopic arm is designed for walls and ceilings, not floors.
Preparation: nails, screws and gaps
Nails and screws
Go over the whole floor. Use a nail punch to drive nail heads a few millimetres below the surface. Drive screws in a little deeper or replace them. Any head that sticks up will rip the abrasive and can damage the drum.
Loose and broken boards
Fix loose boards back down to the joists. Replace broken boards with a board of the same thickness and timber.
Gaps between boards
Narrow gaps can be filled after the coarse sanding pass with a mix of fine dust from the same floor and a gap filler or wood filler. For wider gaps, glue thin slivers of timber into the gap and sand them flush. Only fill gaps once the floor is dry and at room temperature, because timber expands and shrinks with the seasons.
How to sand a wooden floor step by step
Coarse sanding
Start with 36 or 40 grit if there is varnish, paint or a lot of dirt on the floor, or with 60 grit if the floor is fairly clean. Sand along the length of the boards, with the grain. Only on a very cupped or uneven floor should you do the first pass diagonally across the boards, then go back to sanding with the grain.
Edges and corners
After each pass, sand the edges with the edging sander using the same grit. Pick up the corners with a detail sander.
Medium and fine sanding
Move on to 80 grit, then to 100 or 120. Each pass removes the scratches left by the previous one. Do not skip a grit.
Remove the dust
Vacuum the floor and the gaps thoroughly. Wipe it over with a slightly damp cloth and let it dry completely.
How do you avoid scratches and dips?
- Keep the machine moving whenever the belt or drum is touching the wood.
- Only lower a drum sander once it is up to speed, and lift it before you stop.
- Work in overlapping passes of about a third of the machine's width.
- Do not press down: the weight of the machine is enough.
- Fit a new belt as soon as you notice it is cutting more slowly.
Finishing with varnish, oil or stain
Once sanded, the wood has no protection. Choose varnish if you want a hard-wearing surface that is easy to keep clean. Choose oil or hardwax oil if you prefer a natural look and want to be able to touch up worn areas later. If you want a different colour, apply a wood stain or a tinted oil first. Sand lightly between coats of varnish with 150 to 180 grit, and always follow the drying times on the tin.
Safety
Wear a dust mask with a P2 or P3 filter, ear defenders and safety glasses. Wood dust is harmful to your lungs, particularly from oak and other hardwoods. Use the dust bag or extraction on the machine and empty it outside.
If you lift a carpet and find old floor covering or adhesive you cannot identify, do not sand it. Old vinyl floor tiles and black bitumen adhesive can contain asbestos. The UK banned asbestos in 1999, so buildings built or refurbished before 2000 may contain it. Have it tested before you disturb it.
Common mistakes
- Leaving nails proud, so the belt tears.
- Sanding across the grain in the final passes, which leaves visible scratches.
- Moving to a fine grit too quickly.
- Filling gaps while the floor is still moving with the seasons.
- Forgetting the edges, which leaves a darker strip along the walls.
Frequently asked questions about sanding wooden floors
Can I sand a wooden floor with a random orbit sander?
For a small floor, yes, but it takes a long time and the result will be less flat than with a floor sander. For a full room or more, hire a floor sander and use the random orbit sander for the final sanding.
Which direction should I sand floorboards?
With the grain, so along the length of the boards. Only on a very uneven floor do you sand the first coarse pass diagonally, and then go back to sanding lengthways.
Which grit should I finish with?
Usually 100 or 120. Going finer is not necessary on floors and can make it harder for oil to soak in and bond.
Can I sand a scaffold board floor?
Yes. Scaffold boards are often rough and uneven, so start with a coarse grit to flatten the surface. If you want to keep the weathered look, only sand lightly with 80 to 120 grit.
In short: sanding wooden floorboards
Punch the nails down, fix loose boards and sand along the grain with a floor sander, working from coarse to fine grit. Do the edges after every pass and never skip a grit. Protect your lungs with a P2 or P3 mask, and finish the bare wood with varnish, oil or stain.
