How to Choose a Sandpaper Grit Progression Before Painting

Choose your sandpaper grit progression by the surface in front of you, not by a fixed list. One practical guide suggests 80 then 120 grit for rough or weathered wood, a light 120 or 150 pass for smooth new lumber, and a light 180 to 220 scuff for glossy old paint. Matte paint may only need a good cleaning.

At each grit change, keep sanding until the scratches from the previous, coarser grit are gone, then move up. Finish by matching the surface to the prep directions for the primer and paint you plan to use.

What Grit Progression Should You Use Before Painting Wood?

Start from the condition of the wood, because rough, smooth, and painted surfaces need different amounts of work. The routes below come from The Craftsman Blog's grit guide. They are practical starting points from one experienced practitioner, not a universal standard.

Rough or weathered wood needs the most work. According to the guide, paint does not adhere well to gray weathered wood, so the goal of the 80-grit stage is to get back to healthy wood. The 120-grit stage then refines the scratches the 80 left behind.

Smooth lumber from the store still needs attention. The guide explains that freshly milled boards can have "mill glaze," a surface so smooth it can look glossy. That slick layer can keep paint from gripping well, which is why it recommends a light 120- or 150-grit pass instead of starting coarse. Jumping to 80 grit on wood that is already flat just adds scratches you then have to remove.

For bare wood going under paint, the guide sets 120, or at most 150, as its usual stopping point. Its reasoning is that this leaves the primer enough "tooth," meaning fine texture, to grip the wood. Treat that as the guide's rule of thumb. If your primer's instructions call for a different surface result, follow the primer.

Previously painted wood is a separate job. On semi-gloss or high-gloss paint, the guide recommends lightly scuffing with 180 to 220 grit until the shine is gone and the surface looks matte. You are not trying to strip the old paint, only dull it. On flat or matte paint, the same source says sanding often isn't needed and a thorough cleaning is the main step.

How Do You Know When to Move to the Next Grit?

Move up only when the scratch pattern from the previous grit is no longer visible. That is the practical handoff point, and it matters more than any set number of passes or minutes.

The reason comes from how sanding works. Each coarser grit cuts deeper scratches. The next, finer grit's job is to replace those deep scratches with shallower ones. If you advance while the coarser marks are still there, the finer paper only polishes around them, and they can show through paint.

The guide gives a firm warning about grit jumps and scratches: don't skip more than one grit in your progression. Its example is starting at 40 grit, then going to 60 or 80, not straight to 100. Skipping too far, it says, leaves swirl marks and an uneven finish.

Turning that warning into a visual check is a working method, not a formal test. Wipe or brush off the dust so you can see the surface clearly. Look for the deeper lines from the last grit. If you still see them, keep going with the paper you have. If the surface shows only the finer, even pattern of the current grit, step up to the next one.

How Do Paint-System Directions Change the Prep?

Your primer and paint can set their own prep requirements, so read them before you decide the sanding is done. Many product data sheets describe the surface result they need rather than naming a grit number.

The Fresh Start primer preparation instructions show how this works. The U.S. technical data sheet for Benjamin Moore Fresh Start Moorwhite Exterior Wood Primer 100, dated January 10, 2020, says surfaces must be clean, dry, and free of dust, heavy chalk, oily deposits, and mildew. It calls for removing loose or scaling paint by scraping, wire brushing, or sanding. It also warns that smooth-planed clapboards or siding must be sanded thoroughly to break the mill glaze so the primer can penetrate and adhere.

Notice what that sheet leaves out: a grit number. It tells you the result to reach, a surface with the mill glaze broken, but not which paper gets you there. This is where the grit routes above fit. A light 120 or 150 pass is one practical way to reach a "glaze broken" condition on smooth boards. The primer's own conditions, such as dust-free and no loose paint, still decide whether you are ready to coat.

These directions apply only to that named primer and that dated sheet. Before you start, pull the current data sheet for the exact primer and paint you bought, usually from the manufacturer's website. If it names a grit, a sheen to remove, or a cleaning step, follow it over any general rule of thumb.

FAQs

How many grits do I need for a paint job?

Usually two or three. The Craftsman Blog notes that most sanding jobs need at least two grits used in sequence, and its author often prefers three. A glossy painted surface may need only one light pass with fine paper, while matte paint may need none.

Why not sand bare wood finer than 150 before painting?

Very fine sanding can make bare wood too smooth for primer to grip well. The guide recommends stopping at 120, or at most 150, so the surface keeps enough tooth for long-term adhesion. Finer grits are more useful later, such as for scuffing glossy paint.

Should I sand primer before the topcoat?

A light pass can help. For freshly primed wood, the same guide suggests one pass with a fine sanding sponge or 150 to 220 grit paper to knock down rough spots and raised grain. Go lightly so you don't sand through the primer.

Do I need to remove sanding dust before painting?

Yes. Dust left on the surface can get in the way of adhesion, and some primer data sheets require a dust-free surface before you coat. Brush or vacuum the dust off, then wipe the surface before you prime or paint.