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

Weathered deck boards can look gray, splintery, and uneven after years of sun and rain. If your coating is failing or the boards feel rough, sanding is the quickest path to clean wood and a finish that actually lasts. The question is which tool to use: a belt sander or a random-orbital (DA) sander? The short answer: use a belt to knock down ridges and cupping quickly on straight runs, then switch to a random-orbital to refine the scratch and prep for stain. Below is a simple, deck-safe routine that stays flat, controls dust, and lands on a stain-ready surface with a tight ladder of 60 → 80 → 120.

Why Sanding Sequence Matters

Decking is usually softwood (pine, fir, cedar) or pressure-treated lumber. Coarse grits remove weathered fibers fast—but they also carve deep grooves that trap pigment and look blotchy if you skip the refinement step. A smart process (1) levels high spots and light cupping mechanically, (2) tightens the scratch field in small, predictable steps so stain lays evenly, and (3) protects edges, fasteners, and board ends where tear-out and gouges start. Keep pressure light, replace paper early, and let the grit do the work.

Tools & Supplies

• Belt sander (3×21 or 3×24) with fresh belts for fast flattening along board length.
• Random-orbital (DA) sander with variable speed and a firm pad for refining.
• Hand sanding block for edges, railings, and nosings.
• Grits: 60, 80, 120 (discs and sheets as appropriate).
• Vacuum/dust extractor or outdoor-rated blower; stiff nylon brush.
• Deck cleaner/brightener (optional but helpful after sanding dust is removed).
• Raking/inspection light or sunny angle for reading scratches.
• PPE: respirator, eye/ear protection, knee pads; work when the deck is dry.

Recommended Grit Sequence

• 60 grit: Brief, controlled leveling of ridges, cupping, and heavy weathering.
• 80 grit: Primary refinement to erase 60 tracks and even the field.
• 120 grit: Final pre-stain pass for a tight, uniform scratch that accepts finish evenly.

Step-by-Step: Fast Flatten, Clean Finish

1. Prep the deck. Tighten or set fasteners below the surface. Sweep debris and scrape loose flaking finish. Work dry—wet fibers smear and clog paper.
2. Map the board faces. Under raking light, pencil a light line along a few boards. These witness marks tell you when each grit has fully done its job so you don’t over-sand.
3. Level quickly at 60 (belt, with the grain). On straight, accessible runs, take long, even strokes with a belt sander with the board length, pressure feather-light. Stop the moment the pencil lines just disappear and high ridges are reduced. For tight control on small areas or near obstacles, switch to a DA or block at 60 Grit (25-pack)—don’t linger; you’re only resetting the surface.
4. Refine at 80 (switch to DA). Vacuum dust, then run a random-orbital at low–medium speed with a firm pad and dead-flat contact. Slightly change direction (shallow diagonals, then finish with the board) so leftover 60 lines stand out. Replace every 60 scratch with a tight, uniform 80 field. Stock a mid-step that cuts cleanly without gouging like 80 Grit (50-pack).
5. Edges, nosings, and rail parts. Do these by hand or with the DA at the current grit. Keep contact flat on nosings to avoid flats and facets. Count strokes—most round-overs happen here.
6. Pre-stain pass at 120. Make a brief, even pass with the DA at 120 Grit (100-pack) to tighten the scratch for more even color and reduced fuzzing. Don’t polish—if the surface starts to shine, you’re pressing too hard or the disc is dull.
7. De-dust and brightener (optional). Vacuum or blow off thoroughly, then brush. If your species benefits from a wood brightener (common after heavy weathering), apply per label and let the deck dry fully before finishing.
8. Finish smart. Apply stain/sealer in shade, maintaining a wet edge. Back-brush puddles and follow spread rates. Test color on an off-cut or hidden area first.

Special Cases

Severely cupped or ridged boards: Belt at 60 just long enough to knock peaks, then move to the DA at 80. If deep defects remain, consider selective board replacement rather than over-grinding.
Softwoods (PT pine, cedar): Keep pressure very light at 120; going finer than 120 can reduce stain uptake.
Hardwoods (ipe, cumaru): Often prefer 80 → 100/120 only; avoid 60 unless absolutely needed. Use manufacturer-recommended prep for dense exotics.
Old film finishes: If the deck has thick, peeling film, chemically strip first to save time and paper, then use 80 → 120 to refine.

Pro Tips

• Let grit work, not pressure. As soon as cut slows, rotate to a fresh section. Pressure creates heat and stripes.
• Belt to set the plane, DA to refine. Keep the belt moving with the grain; never across boards. The DA bridges minor dips and erases belt lines.
• Alternate directions. A shallow diagonal at each grit reveals leftover scratches instantly—finish passes with the board length.
• Mind fasteners. Exposed screw heads shred discs. Set or countersink before you sand.
• Work in shade. Hot boards soften resins and load paper. Early morning or late day is friendlier on both tools and wood.

Aftercare

• Keep traffic light until the coating cures; follow the product’s re-entry guidance.
• Clean seasonally with deck soap and a soft brush—avoid harsh pressure washing that raises grain.
• Plan maintenance coats before the deck looks tired; a light 120 scuff and recoat extends life dramatically.
• Use furniture glides and avoid dragging metal across boards.

FAQs

• Can I skip 60 and start at 80? Yes, if the deck is only lightly weathered. Use 60 briefly only where ridges or cupping demand it.
• Is 150 or 180 better before stain? On most decking, 120 is the sweet spot—finer grits can reduce penetration and cause uneven color.
• Should I sand railings the same? Similar idea, but stay gentler: 80 → 120 by hand or DA at low speed to avoid flats on profiles.
• Why do I see stripes after staining? Likely leftover 60 lines or belt dwell. Re-enter locally at 80 → 120, then touch up finish.
• Do I need dust extraction outdoors? It helps discs cut cooler and cleaner, but a stiff brush + blower can suffice. Always wear a respirator.

Watch & Learn

Closing: For deck resurfacing, let each tool do what it’s best at: a belt sander for quick, straight-line leveling and a random-orbital for uniform, stain-ready refinement. Keep the ladder tight—60 → 80 → 120—and embed discipline into each step with fresh abrasives and light pressure. Stock exactly what you need so you stay on sequence: reset trouble spots with 60 (25-pack), replace coarse tracks cleanly with 80 (50-pack), and land a uniform pre-stain surface with 120 (100-pack). Do that, and your next coat will look even, feel smooth, and last longer.