80 Grit vs 100 Grit Sandpaper for Floors

The choice between 80-grit and 100-grit as your final drum sander pass is one of the most consequential decisions in hardwood floor refinishing. This grit determines surface uniformity, how well stain accepts, and whether your finish will look professional or flawed. The answer depends entirely on your finish type and specific floor condition.

Understanding Grit and Floor Surface Preparation

In the NWFA (National Wood Flooring Association) grit sequence, 80-grit and 100-grit are not intermediate grits—they are the final drum sander passes. What comes after depends on your finish type:

• Oil-based polyurethane: Can be applied directly over 80–100 grit; no additional sanding required
• Water-based polyurethane: Requires 100–120 grit minimum; must then use a 120-grit buffer screen before finishing
• Site-finished acid-cured lacquer: Typically stops at 60–80 grit due to UV aging considerations

The fundamental difference: 100-grit creates a slightly smoother surface than 80-grit, which affects stain color development, finish adhesion, and the visibility of any sanding scratches after the wood is stained.

80-Grit Sandpaper: Characteristics and Applications

What 80-Grit Does

80-grit leaves visible scratch patterns on the wood surface. These scratches are uniform and acceptable for darker stains or if a buffer screen (120-grit) will be used for final preparation. The grit size is approximately 0.2 mm—the scratches are subtle but present under magnification or raking light.

Advantages of 80-Grit

• Faster cutting: More material removed per pass; useful on heavily damaged or stained floors
• Better for hide-it finishes: If applying dark stain or semi-transparent finishes, 80-grit marks are completely hidden
• Extended abrasive life: 80-grit sheets last longer than 100 or 120-grit due to fewer cuts per area
• Adequate for oil-based poly: Oil-based polyurethane fully hides 80-grit scratches and bonds well
• Cost-effective: Slightly less expensive per sheet than 100-grit
• Professional standard: Most commercial refinishing uses 80-grit as the final drum pass to save time and material

Disadvantages of 80-Grit

• Visible with clear finishes: On natural or light-stained floors with clear polyurethane, 80-grit scratches may be visible under certain lighting
• More particle sanding required: If applying water-based poly, you must do a 100–120 grit buffer screen pass afterward to hide the scratches
• Not ideal for light wood: Pine, ash, or other light woods may show scratch patterns unless heavily stained

When to Use 80-Grit as Final Pass

• Oil-based polyurethane finish is planned
• Dark or medium stain will be applied (hiding scratches)
• Floor has moderate damage requiring aggressive refinishing
• Budget and time are limited
• A buffer screen (120-grit) will follow for final preparation

100-Grit Sandpaper: Characteristics and Applications

What 100-Grit Does

100-grit creates finer scratch patterns than 80-grit (approximately 0.15 mm). These scratches are less visible to the naked eye under normal lighting, though still present under magnification. 100-grit represents a middle ground between the cutting power of 80-grit and the smoothness of 120-grit.

Advantages of 100-Grit

• Smoother surface appearance: Scratches less visible to naked eye, especially with side lighting
• Better for light finishes: Clear stains and natural finishes look more professional
• Improved stain acceptance: Slightly finer grit creates more uniform stain application
• Less buffer sanding needed: Even with water-based poly, can proceed directly to 120-grit buffer without additional drum sanding
• Professional appearance: Creates a more refined looking floor in natural or light-stained finishes
• Compromise solution: Good balance between cutting speed and final surface quality

Disadvantages of 100-Grit

• Slower cutting than 80-grit: Takes slightly longer per pass; less efficient on very damaged floors
• Higher abrasive cost: 100-grit sheets cost 5–10% more than 80-grit
• Still visible on light woods: Without darker stain, scratch patterns remain visible compared to 120-grit
• Marginal improvement over 80-grit: The visual difference is subtle; may not justify the added time for commercial applications

When to Use 100-Grit as Final Pass

• Natural or light-stained finish is planned
• Water-based polyurethane will be applied (better substrate for poly adhesion)
• Homeowner requests maximum surface smoothness
• The floor has minimal damage (no heavy restoration needed)
• Budget allows for additional sanding time

80-Grit vs 100-Grit Comparison Table

Factor	80-Grit	100-Grit
Scratch Visibility	Visible under raking light	Subtle; less visible
Cutting Speed	Fast	Moderate
Abrasive Life	Longer (more material removed per area)	Shorter (finer particles)
Cost per Sheet	$	$$
Oil-Based Poly	Excellent; scratches fully hidden	Excellent; imperceptible scratches
Water-Based Poly	Acceptable (requires 120 buffer screen)	Better; less buffer sanding needed
Light Wood/Natural Stain	Fair; scratches visible	Good; scratches subtle
Dark Stain	Perfect; scratches hidden	Perfect; scratches hidden
Best Use	Oil-based finish, dark stains, tight budgets	Water-based finish, light finishes, premium jobs

Which Grit for Your Finish Type: The Decision Framework

Oil-Based Polyurethane

Oil-based polyurethane is more forgiving of surface texture because the finish material is thicker and more opaque than water-based poly. The finish fully obscures any 80-grit scratch patterns.

Recommendation: 80-grit is adequate and preferred because it allows faster sanding, extends abrasive life, and costs less. The finish will look identical to 100-grit once polyurethane is applied. Professional contractors almost universally use 80-grit for oil-based finishes.

Process: 36 → 60 → 80 (final drum) → polyurethane (no buffer screen needed)

Water-Based Polyurethane

Water-based polyurethane is thinner and more transparent than oil-based. It highlights surface texture more visibly. Additionally, water-based poly requires finer surfaces for optimal adhesion—applying water-based poly over 80-grit can sometimes show adhesion issues in high-traffic areas.

Recommendation: 100-grit minimum, then 120-grit buffer screen for professional results. If budget constraints require 80-grit, you must follow with a 120-grit buffer screen pass to hide the scratches and improve adhesion.

Recommended process: 36 → 60 → 80 → 100 (final drum) → 120-grit buffer screen → water-based polyurethane

Or budget-conscious: 36 → 60 → 80 → 120-grit buffer screen → water-based polyurethane (skip 100-grit)

Pre-Stain Wood Conditioner (Water-Based Finishes)

Water-based stains and pre-stain conditioners are very sensitive to surface grit. The conditioner raises wood grain slightly and requires a smooth substrate for even color.

Recommendation: 100-grit minimum, 120-grit preferred before stain application. If using a pre-stain wood conditioner (essential for softwoods like pine or ash), always go to at least 100-grit drum sanding, then 150–180 grit hand sanding or screen sanding after the conditioner dries.

Acid-Cured Lacquer (Site-Finished)

Acid-cured lacquers (Swedish or similar finishes) are mixed and applied on-site. These finishes cure through chemical reaction rather than evaporation, and surface grit is less critical because the finish bonds differently than polyurethane.

Recommendation: 60–80 grit is standard. Going finer doesn't improve results significantly. Many contractors stop at 60-grit and skip the 80-grit pass for these finishes.

Natural or Light Stain with Clear Poly

This is where grit selection matters most aesthetically. The wood grain is visible, and sanding scratches will show as subtle lines under certain lighting angles.

Recommendation: 100-grit minimum, 120-grit preferred. Consider: 36 → 60 → 80 → 100 (final drum) → 120-grit buffer screen → light stain → water-based or oil-based polyurethane. If premium finish is expected, add a final 150-grit hand sanding pass after stain application but before finishing coats.

NWFA Standard Grit Sequence and Grit Selection

The National Wood Flooring Association provides guidance on grit sequencing. The standard NWFA sequence is:

Pass	Machine	Grit	Purpose	Notes
1	Drum	36	Remove old finish, heavy scratches	Aggressive pass; may require two passes on damaged floors
2	Drum	60	Remove 36-grit scratches	Critical for uniform color appearance
3	Drum + Edger	80	Final aggressive pass, begin edge sanding	Last drum sander pass for many jobs
4	Edger	100	Perimeter matching and final edges	Optional; depends on finish type
5	Buffer with Screen	120	Surface preparation and burnishing	Required for water-based poly; optional for oil-based

Key NWFA guidance: The grit sequence should not be skipped. Jumping from 60-grit directly to 120-grit without the intermediate 80-grit pass results in visible scratches. Similarly, you cannot go directly from 36-grit to 100-grit.

Common Mistakes with Grit Selection

Using Only 80-Grit for Everything

Some contractors stop at 80-grit for all jobs regardless of finish type. This is cost-effective but produces visibly inferior results on light stains and water-based finishes. The scratch patterns are subtle but present, especially under side lighting.

Not Accounting for Stain Color in Grit Selection

Dark stains (ebony, espresso, dark walnut) completely hide sanding scratches. Light stains (natural, golden oak, whitewash) reveal scratches clearly. Grit selection should match finish plan—know your stain before finalizing the sanding sequence.

Skipping the 60-Grit Pass

Some DIYers go 36 → 80 or 36 → 100 to save time. This doesn't work. The 60-grit pass is critical for removing 36-grit scratches. Skipping it results in visible scratch patterns even under dark stain.

Assuming Water-Based Poly Can Skip Finer Grits

Water-based polyurethane requires finer surface preparation than oil-based. If you use 80-grit with water-based poly without a 120-grit buffer screen, you risk:

• Visible scratch patterns that show through the finish
• Potential adhesion issues in high-traffic areas
• Uneven stain acceptance if staining is part of the project

Complete Finishing Sequences by Scenario

Scenario 1: Oil-Based Poly, Dark Stain, Budget-Conscious

Sanding sequence: 36 → 60 → 80 (final)

• 3× 8×19.5" drum sheets in 36-grit
• 2× 8×19.5" drum sheets in 60-grit
• 2× 8×19.5" drum sheets in 80-grit
• 3× 7" edger discs in 80-grit
• 1× 120-grit buffer screen (optional; skipped if cost is primary concern)
• Apply dark stain
• Apply oil-based polyurethane (2–3 coats)

Scenario 2: Water-Based Poly, Natural Finish, Premium Results

Sanding sequence: 36 → 60 → 80 → 100 → 120-grit buffer screen

• 3× 8×19.5" drum sheets in 36-grit
• 2× 8×19.5" drum sheets in 60-grit
• 2× 8×19.5" drum sheets in 80-grit
• 2× 8×19.5" drum sheets in 100-grit
• 3× 7" edger discs in 80-grit
• 2× 7" edger discs in 100-grit
• 2× 120-grit buffer screens
• Optional: Final 150-grit hand sanding pass
• Apply water-based polyurethane (3 coats minimum)

Scenario 3: Oil-Based Poly, Medium Stain, Time-Conscious Commercial Job

Sanding sequence: 36 → 60 → 80 (final)

• 3× 8×19.5" drum sheets in 36-grit
• 2× 8×19.5" drum sheets in 60-grit
• 2× 8×19.5" drum sheets in 80-grit
• 3× 7" edger discs in 80-grit (single pass)
• 1× 120-grit buffer screen
• Apply medium stain
• Apply oil-based polyurethane (2 coats)

Visual Comparison: How 80 vs 100 Grit Appears

Under raking light (side lighting at a shallow angle), the difference is visible:

• 80-grit surface: Fine linear scratches visible; pattern uniform across the floor
• 100-grit surface: Scratches less visible; may see them under extreme side lighting but much subtler
• 120-grit buffer screen: Minimal visibility; practically undetectable to naked eye in normal room lighting

Once stain and finish are applied, the visibility reduces further. Dark stain eliminates visible scratches from any grit. Water-based poly on 80-grit may show subtle texture; water-based poly on 100-grit looks smooth.

Decision Guide Summary

Choose 80-grit final pass if:

• Oil-based polyurethane finish is planned
• Dark or medium stain will be applied
• Budget is a primary constraint
• Floor has significant damage (aggressive cutting needed)

Choose 100-grit final pass if:

• Water-based polyurethane finish is planned
• Natural or light stain finish is desired
• Premium results are expected
• Budget allows for additional sanding time

Best practice compromise: Use 80-grit for the final drum sander pass, then always follow with a 120-grit buffer screen pass. The buffer screen removes 80-grit scratches and provides final surface preparation regardless of finish type. This approach saves time while ensuring professional results.