Orbital vs Belt Sander for Deck Resurfacing: When Each Wins

Resurfacing a weathered deck is part wood science, part smart tool choice. The big question is whether to reach for a random-orbital (DA) sander or a belt sander. One shines at refinement without gouges; the other erases defects fast—but can flatten the wrong places just as quickly. This guide explains exactly when each wins (and fails), and it gives you a proven grit ladder for cedar, redwood, and pressure-treated pine so stain takes evenly and boards stay flat.

Why Sanding Matters Before You Stain

Deck wood is exposed to UV, rain, and foot traffic. Power washing raises fibers; old coatings flake; resin pockets and soft earlywood wear faster than latewood. Sanding isn’t just about making it smooth. Done right, it (1) levels raised fibers without dishing soft zones, (2) removes gray oxidized layers and failing finish, and (3) leaves a uniform scratch field that absorbs stain evenly. Done wrong, it rounds edges, leaves ripples, and burnishes the surface so your stain won’t bite.

Tools & Supplies

• Random-orbital (DA) sander (5–6 in.) with dust extraction; add a thin foam interface pad only on slightly crowned boards.
• Belt sander (3x21 or 3x24 in.) with a flat platen for fast leveling on stubborn boards.
• Firm hand block for edges, rail caps, and stair nosing.
• Wet/dry silicon-carbide sandpaper sheets in outdoor-friendly grits.
• Vacuum/leaf blower, nylon brush for cleaning abrasive faces, and tarps to protect plantings.
• Exterior deck cleaner/brightener (optional pre-sand), raking light or bright sidelight, and painter’s tape for hardware and siding.
• PPE: respirator, hearing/eye protection, knee pads, sun protection.

Grit Sequence (Deck-Friendly)

• 60 grit: Heavy reset—remove gray oxidation, flaking coatings, and raised fibers after washing.
• 80 grit: Primary refinement—replace 60 tracks and even the field without burnishing.
• 120 grit: Final prep before stain; tight, stain-friendly tooth that avoids shiny burnish spots.

Orbital vs Belt: When Each Wins (and Fails)

Random-Orbital (DA) Wins: best for general deck surfaces that are mostly sound but fuzzy from washing. It follows slight crowns without digging, leaves a forgiving scratch signature, and minimizes waves. Fails when you try to level serious cupping, ridges, or thick failing film—too slow; you’ll be tempted to press (heat = burnish).

Belt Sander Wins: best for localized heavy defects: proud seams, thick old coating islands, ridged boards, and high spots. It erases fast and stays straight with two-handed control. Fails when you freehand across soft earlywood or into edges—one second of tilt creates a dish you’ll see forever in raking light.

Step-by-Step: Flat Boards, Even Color

1. Clean first. Use a deck cleaner/brightener to remove mildew and grime, then let the deck dry fully (often 24–48 hours). Sanding wet fibers tears them into fuzz you’ll chase later.
2. Map the surface. In angled sunlight or under a raking work light, pencil a light crosshatch on a few representative boards. These witness marks tell you when a grit has finished its job—no extra cutting.
3. Heavy reset where needed (60 grit). For broad areas that are gray or fuzzy but not coated, start with a DA at low/medium speed, pad dead-flat, feather-light pressure. Where coating islands or ridges remain, spot-level briefly with a belt sander running parallel to the board. Stop the instant the pencil map fades uniformly and the gray is gone. For fast, predictable cut at this stage, stock 60 Grit (25-pack) for hand blocks and detail zones.
4. Primary refinement (80 grit). Switch to the DA everywhere and replace the 60 field with 80 Grit (25-pack). Change your pass direction slightly (still along the board) so any leftover 60 lines pop under light—then finish with-the-grain. Keep the sander moving; don’t lean. If you must touch a stubborn hump, feather a short belt pass and immediately blend with the DA at 80.
5. Edge and detail control. Hand-sand rail caps, baluster flats, and stair nosing with a firm block at 80. Count strokes (e.g., two per edge) to avoid rounding profiles. Keep belts and DAs off crisp outside corners—finish those by hand.
6. Final prep (120 grit). For even stain absorption and a touch-friendly feel, take a quick, light pass with 120 Grit (25-pack) on the DA. You’re not polishing; you’re tightening the scratch field. If you see shine, you’ve burnished—back up to 80 lightly and re-refine.
7. Dust control. Vacuum or blow the surface thoroughly, then wipe rail tops with a clean microfiber. Dust left behind becomes rogue coarse grit under your finish brush or pad.
8. Stain or coat promptly. Apply stain in the shade, keep a wet edge, and back-brush to even lap marks. For solid-color finishes, follow the label’s spread rate and recoat windows. Avoid heavy build on board edges; it peels first.

Special Cases

Severely cupped or ridged boards: Use the belt sander sparingly in lanes with both hands, platen flat, moving in the board’s length. Immediately follow with the DA at the same grit to erase belt tracks. Replace boards that would require deep grinding to flatten.

Softwoods (cedar/redwood): Keep pressure minimal. Stop at 80–120; finer grits burnish and reduce stain uptake. Work in the cool of the day; warm boards fuzz and glaze more easily.

Pressure-treated pine: Fully dry stock sands more predictably. If boards still read damp internally, expect raised fibers; plan a quick 120 de-fuzz pass the next day before coating.

Old film finishes (poly/paint): If a finish is bonded and thick over large areas, chemical stripping plus a rinse may be faster and safer than grinding with a belt. Sand to uniform wood afterward with the 60 → 80 → 120 ladder.

Pro Tips

• Let grit do the work. If cut slows, switch to a fresh sheet—pressure just makes heat and burnish.
• Belt control = two hands, straight lanes. Never cross-grain or nose into edges. Feather in, feather out.
• DA speed sanity. Large-orbit/high-speed settings print halos at fine grits. Drop speed at 120.
• Alternate directions. A slight angle shift at each grit reveals leftover scratches instantly.
• Shade is your friend. Sanding and staining in direct sun raises temperature, drives moisture, and causes flash-dry lap marks.
• Tape the house wall & hardware. A minute of masking beats hours of cleanup.

Aftercare

• Respect recoat/cure times before heavy traffic, planters, or grills.
• Keep grit off the deck: door mats at entries and felt pads under furniture.
• Clean with mild, deck-safe cleaners—avoid harsh alkalines that strip new stain.
• Plan maintenance: a light 120 de-fuzz and a maintenance coat before the surface turns chalky extends life.

FAQs

• Is 40 grit faster? Yes—and it’s also deep. You’ll carve troughs you can’t hide. 60 removes fast enough without scarring most deck woods.
• Can I finish at 150 or 180? For stain, 120 is a sweet spot. Finer grits can burnish and reduce absorption—test on a scrap before committing.
• Why do I still see stripes after staining? That’s leftover coarse scratch or belt tracks. Back up to the previous grit, fully replace the field, and recoat.
• Can I use a drum floor sander? Not recommended. Deck boards aren’t flat enough; drums telegraph every crown and dip.
• Mesh vs standard paper? Mesh helps with dust outdoors, but standard sheets usually leave a tighter, stain-friendly scratch—either works if you keep sheets fresh and pressure light.

Watch & Learn

Closing: Use both tools strategically: the belt for quick, flat spot-leveling, and the DA everywhere else to leave a uniform, stain-ready field. Keep the ladder simple—60 → 80 → 120—and resist pressure that causes heat and burnish. Stock the exact sheets so you stay disciplined at each step: reset stubborn areas with 60 Grit (25-pack), refine universally with 80 Grit (25-pack), and leave a tight, stain-friendly surface with 120 Grit (25-pack). Do that, and your deck will look sharp, take color evenly, and stand up to weather.