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How to sand a deck in one line: set every nail and screw below the surface, sand the deck boards with the grain at 60 grit (40 only where old paint or stain is thick), go over them again at 80 grit and stop there, then hand-sand or detail-sand the edges, railings and stairs to the same 80 grit and remove every bit of dust before you stain. Deck sanding is coarse work by design: a penetrating deck stain needs open pores, so the fine grits you’d use on furniture would ruin it.
This guide is about the sanding itself: when a deck needs it, what grit sandpaper to use, which sander does which part, and how to sand the boards, the gaps, the end grain, the railings and the stairs. If you’re still choosing a machine, be sure to read my article on the best sanders for decks; for the cleaning, weather and stain steps that come after, see how to stain a deck.
⚡ Quick Answer
Grit: start at 60, finish at 80, and never go finer before a penetrating stain. Use 40 only on thick, peeling finish. The full deck grit table is below.
Tools: a belt sander or rented floor sander for the boards, a random orbital to even out the scratches, and a detail sander or sanding sponges for railings and edges.
Then: vacuum, clean and stain within days, before the bare wood starts to weather again.
How to Sand a Deck: The Short Version
- Check whether the deck needs sanding at all with the water test below.
- Pick a dry spell. The boards have to be dry before you sand, and you’ll want to stain soon after.
- Clear and repair the deck: furniture off, fasteners set below the surface, cracks filled.
- Wash off dirt and mildew if there is any, then let the deck dry completely.
- Sand the deck boards with the grain at 60 grit, then 80.
- Sand the edges, the end grain and the gaps between boards.
- Sand the railings, balusters and stairs by hand or with a detail sander.
- Remove the dust, check in raking light, and stain within the same dry spell.
What Grit Sandpaper for a Deck?
Sand a weathered deck with 60 grit and stop at 80 grit before a penetrating stain. Use 40 grit only where old, peeling stain or paint is thick. Going finer than 80 is the most common deck sanding mistake: Sikkens tells you to sand both new and weathered decks with 60 to 80 grit, Ready Seal says “if you absolutely have to sand, use 60 or 80 grit”, and Wood Defender prefers a 60-grit pad “to help prevent closing the wood pores”. Cabot allows 80 to 100 for its semi-solid stain.
| Your deck | Start with | Finish with |
|---|---|---|
| Gray, weathered boards before stain | 60 | 80 |
| New, smooth deck boards | 60 or 80, one light pass | 80 |
| Peeling stain or paint | 40 on the thick spots | 60, then 80 |
| End grain and board edges | 60 | 80 |
| Handrails | 60 | 80, or 100 at most |
Why Not Finer Than 80 Before Stain?
A penetrating deck stain has to soak into the wood to work. Fine sandpaper burnishes the surface and closes the pores, so the stain sits on top, looks blotchy and wears off early. Ready Seal warns that on sanded boards you may only get one light coat to soak in. That is the opposite of furniture, where you sand to 150 or 180 before stain. Sherwin-Williams’ general exterior wood guide does go up to 180 or 220, so if your stain maker gives a grit, follow your stain maker.
What Grit Sandpaper to Get Paint Off a Deck
Start at 40 grit on a belt sander or a rented floor sander for thick, peeling paint or solid stain, move to 60 once the boards are mostly bare, and finish at 80. Change the paper as soon as it loads up with paint. If the paint could date from before 1978, test it for lead before you sand; Cabot’s data sheets carry the same EPA warning. Stripping chemically first and then sanding lightly at 60 to 80 makes less dust.
Grit and the Stain You Buy
Once the deck is sanded, the condition of the boards also decides how much stain you need: weathered and freshly sanded wood takes more than new boards. My deck stain calculator works out the gallons and cost for your deck, railings and stairs. For grits on every other surface, from furniture to drywall to car paint, see the sandpaper grit chart.
Does Your Deck Need Sanding?
Not every deck does, and sanding a sound deck only removes wood you’ll want later. Sprinkle some water on the boards in a few places, including the sunniest ones:
- Water beads up: the old finish is still working. Clean the deck and wait, or recoat with the same product if the color has faded.
- Water soaks in within seconds: the finish has worn through. If the wood is still smooth, a cleaner and brightener may be all the prep the next coat needs.
- The boards are gray, fuzzy, splintered or peeling: that’s when you sand. Gray fibers, raised grain and patches of failing finish are exactly what a 60-grit pass removes.
Sand or Strip?
Some stain makers would rather you didn’t sand. Ready Seal advises against it unless you have to, because sanding closes the pores, and its protocol removes old finish with a stripper and a pressure washer instead. TWP accepts any of the three: a stripper, sanding at 60 to 80 grit, or power washing. PPG’s data sheet for Sikkens SRD does the opposite and asks for a 60 to 80 grit sanding on every deck. In practice, a stripper is quicker on a big deck with a lot of old film, and sanding is better for gray, fuzzy boards and splinters. Many decks get both: strip the film, then a light 60 to 80 grit pass to even out the surface.
Pressure Washing Is Not Sanding
A pressure washer removes dirt, mildew and loose finish, but it also raises the grain, and too much pressure tears the soft earlywood out of the boards. Keep it low: Ready Seal suggests no more than 800 to 1,200 psi, and PPG 500 to 800 psi with the nozzle 8 to 12 inches from the wood. Then let the deck dry fully before any sanding, or the paper will clog almost at once.
Which Sander for Deck Sanding?
Every part of a deck suits a different tool. You don’t need all of them, but you’ll want at least one machine for the boards and something small for the railings.
| Tool | Best for | Watch out for |
|---|---|---|
| Rented drum or orbital floor sander | Large, flat decks with heavy gray wear or old film | Every fastener set below the surface; a drum gouges if it stops moving |
| Handheld belt sander (3″ or 4″ belt) | Stripping weathered boards on most home decks | Keep it moving with the grain; tilting it digs a dip |
| Random orbital sander | Evening out belt-sander scratches, small or lightly worn decks | Slow as a first pass on rough boards |
| Detail sander | Railings, balusters, stair corners, around posts | Far too slow for the deck floor |
| Sanding sponges and folded paper | Handrails, spindle profiles, board edges in the gaps | Use the same 60 and 80 grits, not the fine sponges |
The specific machines I recommend, from the Makita 9403 belt sander to a detail sander for railings, are compared in my best sanders for deck refinishing guide. If you’d rather rent a floor sander for a big deck, my floor sander rental guide covers the machine types, and belt sander vs. orbital sander explains the trade-off between the two handheld options.
Step 1: Prepare the Deck
Clear everything off the deck, then sweep it with a stiff push broom. Walk every board and look at the fasteners: a nail or screw head that sits proud will tear a sanding belt in seconds and can damage the drum or pad. Drive nails a little below the surface with a nail set and screws until the heads sit just under the wood. Screw down any boards that have lifted or cupped away from the joists, and replace boards that are split or soft.
Clear the gaps between boards with a putty knife or a thin scraper: packed gaps hold water against the board edges and stop the deck from draining. Fill cracks, holes and gouges now, before you sand, so the filler gets sanded flush with the rest of the board in your first pass. Use an exterior-rated product; a two-part epoxy putty like the one below won’t shrink back out of the hole.
Wash First If the Deck Is Dirty
Sanding a dirty or mildewed deck loads the paper with grime and grinds it into the grain. If the boards are dirty, green or black with mildew, wash them with a deck cleaner, rinse, and let the deck dry completely before you sand; Cabot asks for 24 to 48 hours after cleaning. A wood moisture meter takes the guesswork out of the wait: Ready Seal asks for 12% moisture or less before its stain, and PPG 18% or less. The makers differ on the order of the remaining steps: PPG cleans, then sands, then applies within a week, while most others put the cleaner and an oxalic acid brightener after the old finish is off. Either way, the boards must be dry when you sand and clean when you stain.
Step 2: Sand the Deck Boards
The boards, the main field of the deck, are where most of the time goes. Always sand with the grain, along the length of each board, never across it. Cross-grain scratches are hard to remove and show clearly under any semi-transparent stain. Work a few boards at a time from one end of the deck to the other, overlapping each pass a little so you don’t leave ridges.
- Softwood decks (pine, cedar, treated lumber): Start at 60 grit. Use 40 only where old stain or paint is thick; softwood cuts quickly and coarse paper can leave dips in the boards. New treated boards must be dry before you sand them: see can you sand pressure-treated wood for the sprinkle test and the dust precautions.
- Hardwood decks (ipe, teak, cumaru): Start at 40 to 60 grit, depending on how much old finish has to come off. Dense hardwood resists the abrasive, so change discs or belts as soon as they stop cutting.
First Pass at 60 Grit
The first pass takes off the gray layer, the raised fibers and whatever is left of the old finish. With a belt sander, set it down already moving, keep it flat and moving along the board, and lift it before you stop: a belt that sits still in one spot digs a hollow in seconds. With a floor sander, follow the rental shop’s instructions and never let the drum rest on the deck while it spins. Change the belt or disc as soon as it stops cutting; a worn abrasive burnishes the wood instead of sanding it.
Second Pass at 80 Grit, Then Stop
Go over the whole deck again at 80 grit to replace the deeper 60-grit scratches with finer ones. Stop at 80 before a penetrating stain: finer paper closes the pores, which is why Sikkens, Ready Seal and Wood Defender all cap deck sanding at 60 to 80 grit (details in the deck grit table above). If you used a belt sander, a random orbital at 80 grit is the best tool for this pass, because it blends the straight belt marks without polishing the wood. Sweep or blow the deck between grits: grit left from the coarse pass gets dragged under the finer paper and leaves scratches.
Step 3: Sand the Edges, End Grain and Between Deck Boards
A floor or belt sander leaves a strip along every board edge, around posts and against the house. A detail sander reaches those strips; its pointed pad gets into the corners where a round or rectangular pad can’t. Sand them at the same 60 then 80 grit, so the color comes out even.
End Grain
The cut ends of the boards absorb stain much faster than the faces, and they’re where decks start to rot and split. Sand them smooth at 60 to 80 grit, no finer, so they take stain evenly, and give them extra stain when you get to that step.
How to Sand Between Deck Boards
You can’t, and don’t need to, sand inside the gaps. What matters is the top edge of each board, where the arrises (the sharp corners) splinter. Round them over lightly with a sanding sponge or folded 80-grit paper run along the edge, then clear the gap with a putty knife and blow out the dust. The stain will reach the sides of the boards on its own when you apply it.
⚠️ Important
Don’t over-sand the edges and end grain. They need to be smooth enough to stop splinters, not polished. A finish at 120 grit and above closes the pores, and the stain sits on the surface instead of soaking in, which leads to peeling.
Step 4: Sand the Railings, Balusters and Stairs
Railings are the part of a deck people touch, so splinters there are a safety problem, not just a cosmetic one. Sand the top cap and the face boards with a detail sander or by hand at 60, then 80. On the handrail itself you can go to 100 at most, the top of Cabot’s range; finer than that and a penetrating stain won’t soak in properly. Run your bare hand along the full length of the handrail when you’re done and sand any rough spot you feel.
Balusters and spindles are faster by hand than with any machine: wrap a sanding sponge or folded paper around them and work up and down. On stairs, sand the treads like deck boards, then the risers and the stringers, and finish the nosings by hand. My guide to the best sanders for stairs covers the tools for awkward angles.
Step 5: Remove the Dust and Check Your Work
Once all sanding is complete, the deck needs to be completely clear of dust before any finish goes on. Vacuum or blow off the entire surface, including the gaps between boards, then wipe the boards with a clean, dry cloth. Dust left behind gets trapped under the stain and leaves a rough texture.
Inspect the deck in good raking light at a shallow angle: this reveals any missed areas, uneven sections, or filler that’s proud of the surface that aren’t visible under overhead light. Address anything you spot now; stain will not hide sanding deficiencies, it will emphasise them. If patches of the old stain survived sanding, my guide on how to remove stain from wood covers stripping it before you recoat.
Sand and Stain a Deck: What Comes Next
Freshly sanded wood starts to weather straight away, so plan the sanding and the staining as one job. Don’t sand and then leave the deck unfinished for weeks: PPG, for example, asks for its Sikkens deck finish to go on within a week of the preparation, and gray, sun-damaged fibers come back quickly on bare wood.
Clean and Brighten After Sanding
Most stain makers want a deck cleaner and an oxalic acid wood brightener on bare wood before the stain: they lift the sanding dust and any remaining gray, neutralize a stripper if you used one, and open the pores. Let the deck dry again afterwards; the water test tells you when it’s ready.
Stain in the Right Weather
Most deck stains need mild, dry weather, no direct sun on the boards and a rain-free window that ranges from 12 to 48 hours depending on the product. The full sequence, from cleaner and brightener to the last coat, is in my guide on how to stain a deck; if you’re still choosing a product, I compare seven in best deck stain.
Deck Sanding Safety
- Dust mask and eye protection for every pass. Pressure-treated wood dust in particular shouldn’t be breathed in; the pressure-treated wood guide covers the precautions.
- Lead paint: if the deck or railings were painted before 1978, test the paint before sanding. Cabot’s and Olympic’s data sheets both carry the EPA lead warning: sanding releases lead dust, which calls for a respirator and HEPA cleanup.
- Hearing protection with belt and floor sanders, and a GFCI-protected outlet or cord outdoors.
- Collect the dust with the sander’s bag or a shop vac rather than blowing it into the garden.
💡 Common Deck Sanding Mistakes
Sanding across the grain. Sanding to 120 or 150 like furniture. Sanding a wet or dirty deck. Leaving nail and screw heads proud. Letting a belt or drum sander sit in one spot. Skipping the edges, end grain and railings. Sanding and then waiting weeks to stain. Each one shows up as scratches, blotches, dips or peeling once the stain goes on.
✨ The Bottom Line
To sand a deck, set the fasteners, sand the boards with the grain at 60 then 80 grit, give the edges, end grain, railings and stairs the same grits by hand or with a detail sander, and remove every bit of dust. Stop at 80 so the stain can soak in, and stain within days, not weeks.
❓ Frequently Asked Questions
What is the quickest way to sand a deck?+
Is it better to strip or sand a deck?+
Can you sand a deck with an orbital sander?+
What grit sandpaper should I use on a deck before staining?+
What grit sandpaper is best for deck railings?+
Do decks need to be sanded before painting?+
How do I know if my deck needs sanding or just cleaning and recoating?+
Conclusion
A properly sanded deck is one of the most satisfying outdoor DIY projects you can complete: the transformation from weathered, gray, rough boards to an even surface ready for stain is remarkable. The rules are simple: sand with the grain, stop at 80 grit, don’t skip the edges and railings, and stain soon after. For the tools, see the best sanders for deck refinishing; for the gallons, my deck stain calculator; and for the next step, how to stain a deck.
