6 minute read -
Sanding Stairs: Step by Step From Old Varnish to Smooth Wood
Sand a staircase from the top down, using a random orbit sander or orbital sander for the treads and a detail sander for corners and edges. Start with 80 grit to remove old varnish or paint, then work up through 120 to 180. If there is a thick or old layer of paint, strip it first, and if the paint could date from before 1992, check it for lead before you do anything else.
This guide to sanding stairs covers the tools and grits you need, when to strip rather than sand, and the order of work that gives you a smooth finish without walking over freshly sanded wood.
What will you learn in this article?
- What do you need to sand a staircase?
- Which sander should you use for which part of the stairs?
- Which grit should you choose?
- Should you strip the stairs first or sand straight away?
- Old paint on the stairs: what about lead?
- Step by step: how to sand a staircase
- Can you keep using the stairs while you work?
- How long does it take to sand a staircase?
- How do you finish the stairs after sanding?
- Common mistakes when sanding stairs
- Frequently asked questions about sanding stairs
- In short: sanding stairs
What do you need to sand a staircase?
- A random orbit sander or orbital sander for the treads and risers
- A detail sander (triangular pad) for corners, edges and the nosing
- Sandpaper in 80, 120, 180 and 240 grit (the last for between coats)
- A sanding block or sanding sponge for spindles and mouldings
- A scraper or filling knife
- If needed, paint stripper, a brush and a nylon scrubbing brush
- A vacuum cleaner, soft brush and damp cloth
- Dust sheets and masking tape
- A dust mask (at least FFP2), safety glasses and gloves
A cordless sander, for example from the Maxxpack 18V range, is handy on stairs because you are not constantly tripping over a cable on the treads. For long, heavy sanding sessions, a sander you can connect to a vacuum cleaner is worth it, as it keeps far more dust out of the house.
Which sander should you use for which part of the stairs?
| Part of the stairs | Sander or method |
|---|---|
| Treads (flat) | Random orbit or orbital sander |
| Risers | Orbital sander or detail sander |
| Corners, edges and nosing | Detail sander |
| Spindles, handrail and mouldings | Sanding sponge or sandpaper by hand |
| Narrow gaps along the wall | Scraper, then sand by hand |
A random orbit sander removes material faster and leaves fewer scratches. The detail sander reaches where a round or rectangular pad cannot.
Which grit should you choose?
The grit depends on what is on the stairs now:
- Thick layer of old varnish or paint: start with 60 or 80 grit.
- Varnished stairs that only need freshening up: start with 120 grit.
- Bare, untreated treads: 120 grit, then 180.
- Between two coats of varnish: a light key with 240 grit.
Do not skip grits. Jumping straight from 80 to 180 means the deep scratches from the 80 grit will still show under the varnish.
Should you strip the stairs first or sand straight away?
A thin layer of varnish can simply be sanded off. With several coats of paint, stripping is quicker and creates less dust:
- Apply the stripper thickly with a brush and leave it for the time stated on the tin.
- Scrape the softened paint off with a scraper, working along the grain.
- Clean or neutralise the wood as described on the packaging.
- Let the wood dry completely before you start sanding.
Ventilate well and wear gloves. Sanding wood that is still damp raises the grain and clogs your sandpaper.
Old paint on the stairs: what about lead?
In houses built before 1992, the lower layers of paint may contain lead. Dry sanding releases it as fine dust. If you are unsure, have the paint tested or use a lead test kit from a DIY store.
Step by step: how to sand a staircase
Prepare the stairs
Remove the stair runner, carpet grippers, nails and staples. Mask the walls and skirting with tape and dust sheets, and cover the floor at the bottom of the stairs.
Fix loose parts
Secure any creaking or loose treads before you start sanding.
Start at the top
Work from the top tread down. That way you never walk on sanded treads and the dust falls on parts you still have to do.
Sand the treads with a coarse grit
Sand with the random orbit sander and 80 or 120 grit along the grain. Keep the sander flat and do not press hard.
Do the corners and nosing
Use the detail sander for the edges along the wall and the rounded nosing.
Sand the risers
Use the same grits, with the orbital sander or detail sander.
Sand the spindles and handrail
Use a sanding sponge, which follows the curves better than a machine.
Fine sand
Repeat everything with 180 grit.
Remove all the dust
Vacuum thoroughly, wipe down with a slightly damp cloth and let it dry.
Can you keep using the stairs while you work?
Yes, with some planning. Sand and varnish every other tread: first the odd-numbered treads, and once they are dry the even ones. That way you always have a tread to step on. Put a note or a strip of tape on the treads that are wet. It does take extra time, so allow a few days rather than one weekend.
How long does it take to sand a staircase?
For an average closed staircase with a thin coat of varnish, the sanding usually takes about a day. If you need to strip paint, or the stairs have a lot of spindles, it will take longer. After that come the drying times of the primer and the coats of varnish, which are given on the tin.
How do you finish the stairs after sanding?
- Choose a hard-wearing stair varnish, oil or stain made for floors and stairs.
- With varnish or paint, apply a primer first if the product calls for one.
- Lightly sand between coats with 240 grit and remove the dust.
- Apply at least two top coats to the treads, as they take the most wear.
Common mistakes when sanding stairs
- Pressing too hard, so the sander leaves dips or waves in the wood.
- Sanding across the grain with the orbital sander.
- Skipping grits.
- Not removing the dust, so specks end up in the varnish.
- Starting at the bottom and then walking over the sanded wood.
Frequently asked questions about sanding stairs
What is the final grit for sanding stairs?
Before varnishing, you usually finish on 180 grit. Sanding finer makes the wood so smooth that some varnishes do not bond as well. Between coats, give a light sand with 240 grit.
Can I sand stairs with just a detail sander?
You can, but it is slow on the flat treads. A detail sander is designed for corners and edges. For the treads themselves, a random orbit or orbital sander is faster and gives a flatter result.
Do I need to sand varnished stairs back to bare wood?
Not always. If the varnish is still intact and you are using the same type of varnish, a thorough sand with 120 to 180 grit is often enough. If you want to switch to oil or stain, the wood does need to be completely bare.
How do I stop the dust spreading through the house?
Connect the sander to a vacuum cleaner, seal doorways with plastic sheeting and keep windows open. Vacuum as you go and wear a dust mask. That keeps most of the dust in the stairwell.
In short: sanding stairs
Work from the top down, use a random orbit or orbital sander on the treads and a detail sander for corners and nosings, and go from 80 or 120 grit up to 180 without skipping steps. Strip thick paint first and check old paint for lead. Remove all the dust before you apply at least two coats of hard-wearing stair varnish.
