6 Best Sandpaper Grits for Paint Stripping Pros Rely On

Stripping paint is often the most grueling phase of exterior restoration, whether working on historic wood siding or refurbishing metal structural components. Selecting the incorrect grit leads to wasted labor, premature sandpaper clogging, and potential damage to the substrate itself. Professional results depend entirely on understanding the material removal rate versus the surface finish required. This guide breaks down the essential grit progression used by trade professionals to ensure efficient, high-quality results.

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40-Grit Sandpaper: The Heavy Lifter for Thick Paint

When faced with alligatoring paint or deep, multi-layered lead-based coatings that have been built up over decades, 40-grit is the starting point. This is an aggressive, coarse abrasive designed to shear through thick material without stalling the motor of a random orbital sander.

It functions much like a wood plane, removing high spots and heavy flakes rapidly. On exterior trim or thick siding, 40-grit minimizes the time spent in the initial phase, though it leaves deep scratches that demand subsequent refinement.

Always exercise caution when using 40-grit on soft wood species like cedar or pine. Excessive pressure in one spot can create divots or gouges that are nearly impossible to feather out later.

60-Grit Sandpaper: For Multiple Layers of Old Paint

Once the thick, loose, and peeling layers are gone, 60-grit becomes the primary tool for leveling the remaining stubborn patches. It strikes a balance between rapid stock removal and manageable scratch patterns.

This grit is ideal for bridging the gap between heavy stripping and surface preparation. It effectively removes the secondary layers of paint that 40-grit might have missed without tearing into the substrate as aggressively.

Contractors often rely on 60-grit for deck railings or window frames where detail work is required. It provides enough bite to clean out crevices while leaving a surface that is easier to smooth during the finishing stages.

80-Grit Sandpaper: The Go-To Stripping Workhorse

If a project requires stripping down to bare wood for a fresh stain or clear coat, 80-grit is the versatile middle ground. It is the most commonly used grit in the professional arsenal because it is aggressive enough to clean stubborn residue but fine enough to avoid irreparable surface damage.

On flat surfaces like exterior panels or board-and-batten, 80-grit allows for steady progress without requiring constant disk changes. It is the gold standard for removing the final traces of paint pigments from the grain of the wood.

Use 80-grit to determine the integrity of the substrate. If the wood remains rough after a pass with this grit, it usually indicates water damage or rot that sanding alone cannot address.

100-Grit Sandpaper: Smoothing After Coarse Grits

After stripping away the bulk of the old finish, 100-grit is used to erase the deep scratch patterns left by the 40 and 60-grit abrasives. It is essentially the transition phase into fine finishing.

This grit does not remove paint layers efficiently, so do not attempt to use it as a primary stripping tool. Its purpose is to homogenize the surface texture, ensuring the final paint or stain will not highlight deep gouges from earlier steps.

Focus on maintaining a uniform pace across the surface. Skipping this step often results in a “sanded” look where the paint highlights every scratch left behind by the coarser discs.

120-Grit Sandpaper: Feathering Edges for Priming

Feathering is the critical technique of sanding the edges where paint was removed so that the transition between bare wood and existing paint is invisible. 120-grit is the ideal choice for this final blending.

This grit smooths the perimeter of the stripped area, preventing the “picture frame” effect that happens when new paint is applied to an uneven transition. It ensures that when the primer goes on, the surface is uniform and smooth to the touch.

For many projects, stopping at 120-grit provides the perfect “tooth” for primer adhesion. Wood fibers are open enough to accept the primer, but smooth enough to provide a professional-grade finish.

150-Grit Sandpaper: For the Final Prep Sanding

150-grit is reserved for high-end finishing work or when applying a clear coat rather than an opaque paint. It is far too fine for stripping, but it is necessary for achieving a glass-smooth surface on architectural details.

This grit should only be used once the surface is entirely clean and stripped of all old coatings. It polishes the wood grain, ensuring that no stray fibers will rise when the paint or stain is applied.

While often considered optional on exterior work, 150-grit is essential for surfaces that will be seen at close range, such as entry doors. A finer surface allows the finish to lay flatter and more evenly.

Open-Coat vs. Closed-Coat: What You Need to Know

The spacing of the abrasive grains, known as the “coat,” is just as important as the grit number. Open-coat sandpaper has gaps between the grains, while closed-coat paper has the surface completely covered.

• Open-coat is mandatory for stripping paint because the gaps prevent the paper from clogging with gummy, peeling paint residue.
• Closed-coat is designed for sanding bare wood or metal where dust is the primary byproduct, but it will clog almost instantly on a painted surface.

Always check the packaging for “open-coat” designation when tackling paint removal. Using closed-coat paper on painted surfaces is a guaranteed way to burn through twice as much sandpaper.

Sanders vs. Hand Sanding: Picking the Right Tool

Random orbital sanders are the heavy lifters of the industry, utilizing a circular and oscillating motion to prevent swirl marks. These are the most effective tools for large, flat areas of siding or trim.

Hand sanding remains a necessity for corners, intricate moldings, and tight areas where an orbital sander cannot reach. A sanding block or a folded piece of paper allows for manual pressure control, which is essential to avoid damaging decorative profiles.

Match the tool to the surface complexity. If the structure has deep architectural details, invest in a detail sander or dedicated hand-sanding tools to ensure the finish remains uniform in the recesses.

Lead Paint Safety: Don’t Skip This Crucial Step

Any home built before 1978 is assumed to contain lead-based paint unless testing proves otherwise. Sanding lead paint creates fine, toxic dust that is a major health hazard to the applicator and the surrounding environment.

Always utilize HEPA-rated vacuum attachments on sanders and wear N100 or P100 particulate respirators when dealing with unknown paint layers. Containment, such as heavy-duty plastic sheeting and negative air pressure zones, is required by law in many jurisdictions.

Never dry-sand surfaces if lead is present. Use wet sanding techniques or chemical removal methods to keep the dust out of the air entirely.

When to Pair Sanding with a Chemical Stripper

There are instances where sanding alone is the wrong approach, particularly when dealing with intricate carvings, historic window muntins, or metal surfaces that cannot be scuffed without losing detail. Chemical strippers break down the binder in the paint, turning it into a sludge that can be scraped away.

Use chemical strippers to remove the bulk of the 10+ layers of paint, then use 80-grit or 100-grit sandpaper to clean the remaining residue. This saves the substrate from over-sanding and prevents the loss of sharp edges on architectural features.

This two-step process is more efficient for large-scale restorations than relying solely on abrasives. It protects the integrity of the material while providing a clean, sanded surface ready for the final finish.

Mastering the progression from 40-grit removal to 150-grit refinement is what separates a amateur finish from a professional-grade restoration. By choosing the right abrasive density and pairing it with proper tools, you ensure that the substrate is protected and the final coat is durable. Proper preparation is not a shortcut; it is the foundation upon which the longevity of the entire project rests.