Orbital vs Belt Sander for Deck Resurfacing: When Each Wins

Your old deck can look brand new again—with the right sander and the right grit sequence. But should you reach for a random orbital sander (ROS) or a belt sander? The answer depends on deck condition, species, and finish goals. This guide breaks down when each tool shines, the grits that actually move the needle on weathered boards, and a field-tested workflow you can follow in a weekend.

Why Sanding Matters on Weathered Decks

Deck boards live a hard life: UV, rain, and foot traffic raise grain, open checks, and leave old coatings patchy. Proper sanding does three critical things: (1) removes failing stain or gray fiber, (2) flattens cupped or ridged boards enough for a uniform appearance, and (3) creates a consistent scratch pattern that helps new coatings wet in evenly. Over-sanding, however, can scallop boards, round board edges, and reduce fastener bite, so control is everything.

Tools & Supplies

• Random orbital sander (5–6 in.) with dust extraction; great for control and blending.
• Belt sander (3×21 in. or 3×24 in.) for fast, straight-line stock removal on tough boards.
• Hand sanding block for edges, railings, and tight spots.
• Vacuum/extractor (HEPA preferred) plus a stiff brush for crevices.
• Wet/dry silicon carbide sandpaper sheets in a practical deck sequence (80 → 120 → 220).
• PPE: respirator, ear/eye protection, knee pads.
• Raking light or a bright work light for quality checks.
• Deck cleaner/brightener for prep and a high-quality exterior stain or sealer for aftercare.

Recommended Grit Sequence for Deck Boards

• 80 grit: Primary cut to remove gray fiber, failed stain, and minor ridges without trenching.
• 120 grit: Refine 80-grit scratches and equalize sheen across mixed boards.
• 220 grit: Optional finishing pass for smooth feel on railings/treads; on open-grain softwoods you can stop at 120 for better stain uptake.

Step-by-Step Workflow (With Smart Tool Switching)

1. Assess & clean. Sweep, vacuum, and wash the deck to remove grit that can scratch during sanding. Mark any proud fasteners and set them slightly below the surface.
2. Choose your primary sander. If boards are heavily weathered, cupped, or ridged, start with a belt sander for a controlled flattening pass. If boards are generally flat with light wear, begin with a random orbital to protect the surface from accidental gouges.
3. Level & strip with 80 grit. On tough zones, a belt sander running with-the-board cuts quickly but must be kept dead flat and moving. Everywhere else, use a ROS with light pressure and long, overlapping passes. For consistent sheet-backed support on hand work and edges, use 80 Grit (25-pack) — aggressive enough to reset weathered fiber without digging trenches.
4. Blend with 120 grit. Switch to the ROS across the whole field to erase 80-grit lines and unify the scratch pattern. Work board-by-board, checking under raking light. For faster progress and fewer swirl risks, keep the pad flat and the extractor on. Stock up on 120 Grit (50-pack) for this bulk refinement stage.
5. Detail edges, railings, and treads. Hand-sand spindles, risers, and nosings. If you want a barefoot-smooth feel on handrails and stair treads, add a light pass with 220 Grit (100-pack). Keep pressure minimal—you're de-nibbing, not reshaping.
6. Vacuum & inspect. Vacuum thoroughly and wipe test boards with a damp cloth. Dull patches or visible 80-grit lines mean you should revisit that area with 120 before you move on.
7. Finish prep. If using a cleaner/brightener system, follow the manufacturer’s timing after sanding, then allow proper dry time before coating. Confirm moisture content is within the finish’s spec (typically under ~15%).
8. Coat. Apply your stain or sealer per label—maintain a wet edge and back-brush between boards to avoid lap marks. The 120/220 scratch field should disappear under a penetrating finish.

Orbital vs Belt: When Each Wins (and Fails)

Random Orbital Sander (ROS)
Wins when the deck is mostly flat, the coating is thin, or you need to blend after a belt pass. It’s forgiving, resists directional scratches, and works well near edges. Fails when you try to use it like a planer—deep cupping or heavy ridges will take forever and tempt you to add pressure, which invites swirl.

Belt Sander
Wins on severe weathering, ridges at board seams, and localized high spots. Its linear scratch pattern is easy to blend later. Fails when used across board joints, at angles, or with too much pressure—hello divots and cross-grain scars. Keep it parallel to boards and moving.

Special Cases

Pressure-treated pine: Stop at 120 on the field to preserve porosity for penetrating stain; over-sanding can reduce uptake.
Cedar/Redwood: Gentle species benefit from ROS-only work; limit belt passes to only the worst ridges and keep grits fresh to avoid burnishing.
Hardwood decks (IPE, cumaru): Dense fibers prefer controlled ROS passes and may warrant finishing at 180–220 before an oil specifically made for exotics.
Paint removal: Sanding thick, elastic paint is risky and slow—consider chemical strippers for bulk removal, then sand to equalize the surface.

Pro Tips

• Keep the pad or platen flat; tipping at board edges creates scallops you’ll have to chase later.
• Let abrasives cut—don’t add weight. Pressure creates heat and swirl without increasing removal rate.
• Vacuum as you go. Dust in the scratch field acts like rogue coarse grit and re-scratches smoothed boards.
• Alternate ROS directions (with-the-board, then slight diagonal) to reveal lingering scratches without creating cross-grain tracks.
• Replace paper early; dull 80 behaves like polished 120 and wastes time.
• Mask metal hardware; hitting screw heads will tear sheets and create black streaks on tannin-rich woods.

Aftercare

• Wait the product’s specified cure time before heavy foot traffic or furniture replacement.
• Clean seasonally with a mild deck wash—avoid harsh bleach mixtures that degrade lignin and finishes.
• Plan a light maintenance scuff (120) and recoat on high-wear zones every 12–24 months depending on climate and exposure.

FAQs

• Can I jump from 80 to 220? Not on deck boards. You’ll lock 80-grit scratches under finish. Use 120 as the bridging grit.
• Will 220 make my stain blotchy? On softwoods, yes—stop at 120 on the field. Use 220 only on rails/treads where touch-feel matters most.
• What about drum floor sanders? Too aggressive for typical deck thickness and fastener layout; risk of waves is high.
• Do I need to wet-sand? No—decks are best dry-sanded with good dust extraction. Wet debris can pack board gaps and stain adjacent masonry.

Watch: Deck Sanding & Blending

Bottom line: Use the belt sander sparingly and purposefully to flatten truly rough boards, then hand the job to the ROS to erase lines and even the sheen. Follow an 80 → 120 (→ 220 for touch zones) sequence, and pair it with quality sheets—80 Grit (25-pack), 120 Grit (50-pack), and 220 Grit (100-pack)—for predictable results you can repeat every season.