Deck Resurfacing: Belt vs Orbital Sander (60–120 Grit Guide)

Decks age hard: UV bleaches lignin, rain raises grain, old coatings flake, and foot traffic mashes fibers flat. If you’re resurfacing, the big choice is belt sander vs orbital (random-orbit) sander. Each shines at different tasks. Used together—belt for fast leveling and coating removal, orbital for blending and finish-prep—you’ll get straight boards with uniform scratch that accepts stain evenly. This guide shows when each tool wins (and fails), the grits to run (60 → 80 → 120), and a step-by-step routine you can repeat on any deck.

Why Sanding Discipline Matters on Decks

Exterior softwoods (pine, cedar) crush and raise easily; hardwoods (ipe, teak) resist cutting and heat up. A disciplined process (1) levels cupping and ridges without gouging, (2) replaces scratches in tight steps so stain doesn’t telegraph belt tracks or halos, and (3) controls heat and dust so you don’t glaze resin or embed grit that causes future splinters.

Tools You’ll Need

• Belt sander (3×21 or 4×24 in.) with a flat, rigid platen; dust bag or extractor.
• Random-orbit (DA) sander with a firm pad (5–6 in.) and variable speed.
• Sandpaper: 60, 80, and 120 grits (belts and sheets/discs).
• Hand sanding blocks (firm) for edges, nosings, and between balusters.
• Driver/bit set and punch to recess screws/nails below the board surface.
• Vacuum/blower, stiff brush, microfibers; tarps to protect landscaping.
• Raking/inspection light (or low sun angle) and a pencil for witness marks.
• PPE: respirator, hearing protection, eye protection; knee pads and gloves.

Recommended Grit Sequence

• 60 grit: Aggressive leveling & coating removal; break glaze.
• 80 grit: Primary refinement; erase 60 tracks and even color uptake.
• 120 grit: Final prep for semi-transparent/solid stains and most topcoats.

Step-by-Step: Flat Boards, Even Color

1. Assess the deck & make it safe. Tighten or replace fasteners; recess all screws/nails below the board surface. Sweep and wash if needed, then allow the wood to dry thoroughly (24–48 hours of good weather). Flag boards that should be replaced rather than sanded thin.
2. Plan your tool zones. Use the belt sander on flat, straight runs to knock down cupping, ridges, and heavy coating. Use the orbital near edges, posts, transitions, and for the final blend. Never belt-sand railings or narrow edges—you’ll round them in seconds.
3. Level at 60 with the belt. Load a fresh belt and set low–medium speed. With two hands on the tool, start moving before the belt touches down. Run long, overlapping strokes with the board’s length and keep the platen dead-flat. For small local highs, wrap a firm block with 60 Grit (25-pack) and kiss down the spot—don’t plow valleys.
4. Refine at 80 and start blending. Where you belted, switch to 80 on the orbital and keep the pad flat at low–medium speed. Slightly change stroke angle so leftover 60 lines pop and disappear. On broad flats, you can also run a fresh 80 belt to speed things up, then immediately follow with the orbital to remove belt tracking. Do edges and nosings by hand or with the orbital using a firm block wrapped with 80 Grit (50-pack) so geometry stays crisp.
5. Handle nosings, seams, and end grain. Do stair nosings and board ends by hand on a firm block at the current grit. Count strokes to avoid rounding. Between tight balusters, wrap a thin block for control. Vacuum often—embedded grit = random scratches at the next step.
6. Final prep at 120 for stain/coat. Switch to the orbital at 120 with feather-light pressure, pad flat, and long, overlapping passes. Your target is an even matte with no visible directional lines. Touch edges and details with a firm block wrapped with 120 Grit (100-pack). Stop the instant your pencil witness marks just disappear—over-sanding can burnish softwoods and reduce stain uptake.
7. De-dust and test stain. Vacuum in two directions, blow out seams, then wipe with a clean microfiber. Test your stain on a small area—if color is blotchy, re-enter locally at 80 → 120 to even the scratch, or use a wood brightener per your finish system.
8. Apply finish smart. Follow the product’s spread rate and timing. Maintain a wet edge and work in shade if possible. On hot days, thinner coats reduce lap marks. For film-forming products, respect recoat windows and de-nib with 120–150 only when the coat powders.

When Each Tool Wins (and Fails)

Belt sander wins: heavy coating removal, cupped or ridged boards, long straight runs, and time savings on large decks. Fails: near edges, seams, curves, or railings; on bouncy boards; and in inexperienced hands where divots and waves appear quickly.
Orbital wins: blending, edge work, nosings, railings, and final prep. Fails: deep leveling—it will follow dips and may polish high spots without flattening.

Special Cases

Deep checks or splinters: Replace boards rather than grinding them flat; aggressive sanding weakens fibers.
Painted decks: For thick, elastic coatings, consider chemical/heat-assisted removal first; belts can smear and clog.
Dense hardwoods (ipe/teak): Run lower speeds, lighter pressure, and expect longer time at 80–120.
Pressure-treated lumber: Let new PT dry several weeks before sanding; wet PT gums abrasives and stains poorly.
Nail heads & screws: Countersink before sanding; striking metal with a belt creates sparks and tears belts, and a DA will throw crescents.

Pro Tips

• Flat platen, flat pad. A cupped belt platen or soft orbital pad makes waves and swirls. Keep contact true.
• Fresh media beats pressure. Rotate to a new belt/disc as soon as cut slows—pressure makes heat, glaze, and random scratches.
• Alternate directions. Slight angle change at each step reveals leftover scratches before you climb.
• Feather your exits. Lift off while moving; never stop with the belt spinning on the wood.
• Mind the weather. Sand and finish in shade on cool boards; hot resinous decks smear and burnish.

Aftercare

• Blow debris from seams before coating; dust left in gaps wicks moisture and can cause failure.
• Respect recoat windows; sanding a green coat smears and clogs.
• Use door mats and furniture pads to minimize grit scratching.
• Plan maintenance: a light 120 de-nib and a thin refresh coat when traffic paths dull—don’t wait for full failure.

FAQs

• Can I skip 80 and go 60 → 120? Not if you want even color. 80 erases 60 tracks and sets a uniform field for 120.
• Will 120 make the deck too smooth for stain? No—used lightly, 120 leaves excellent tooth and even uptake on most species. Avoid burnishing by keeping pressure light and sheets fresh.
• What orbit size is best? Smaller orbits hide paths better; any DA works if kept flat with tight grits.
• How do I avoid edge rounding? Keep machines off nosings and edges; do them by hand on a firm block at the current grit.
• Is power washing a substitute? It cleans but raises grain and can erode soft springwood. Use it as prep, then sand per the ladder.

Watch & Learn

Closing: Let each tool do what it’s best at. Use the belt to level and break through old coatings at 60 (25-pack), hand and orbital sanders to refine uniformly at 80 (50-pack), and finish with a quick, even 120 (100-pack) pass for a stain-ready surface. Keep the pad flat, pressure light, and steps tight—and your deck will look straight, accept color evenly, and weather better.