The short answer: Look at an exposed edge, not the surface of the floor.

• A closet threshold, floor vent cutout, or a loose transition strip usually shows a cross-section of the board.
• A thin putty knife slid between boards (where finish isn’t blocking access) can help locate the tongue-and-groove line.
• Calipers give the most precise reading if the edge is accessible.

Signs a floor has already reached its limit:

• Visible nail heads at or near the surface.
• The tongue-and-groove line itself is starting to show through.
• Individual boards that look noticeably thinner than their neighbors, or have started to split at the edges.

If any of these show up during an inspection, that’s a sign to stop and reconsider rather than push forward with a full sanding.

The short answer: Yes. Nail-down floors generally tolerate more aggressive sanding than glue-down floors.

• Nail-down solid floors are fastened mechanically, so there’s less risk of disturbing the installation itself during a sand.
• Glue-down solid floors rely on an adhesive bond to the subfloor, and overly aggressive sanding can generate enough heat and vibration to affect that bond over time.
• Either way, the tongue-and-groove measurement is still the deciding factor; the installation method just changes how much margin for error there is.

The short answer: Start with a test patch, not a guess, and never skip more than one grit level at a time.

The standard test: Run a 36-grit belt across a 4-foot by 4-foot section in the worst-looking part of the floor.

• If that section comes out clean and bare, even at the board edges, 36 grit is your starting point.
• If it’s not fully clean, drop down to 24 grit and test again.
• Most floors that haven’t been refinished in 20 to 30 years, or that have several old layers of finish, need that 24-grit start.

A common full-refinish sequence:

• 24 or 36 grit: removes the old finish and any surface damage.
• 60 grit: removes the scratch pattern left by the coarser grit.
• 80 grit: the final sanding grit for most standard floors.
• 100 grit: often used instead of 80 as the final grit on floors that will be stained, or on lighter woods like maple and birch.
• 120 to 150 grit screen: not a sanding step, used on a buffer to lightly abrade the surface between coats of finish.

Why skipping grits causes problems:

• Jumping from 36 straight to 80 leaves deeper scratches that the finer grit can’t fully remove.
• Those leftover scratches show up more once stain or finish is applied, since pigment settles into them and makes them more visible, not less.
• Following the sequence in order, without skipping more than one level, keeps the surface consistent from room to room.

We stock the full range of belts, discs, and screens needed to run this sequence properly, including 3M Regalite and Resinite abrasives across the grits mentioned above.

The short answer: Harder species tolerate more aggressive sanding than softer ones, but the tongue-and-groove measurement still applies to all of them.

• Oak, maple, and hickory hold up well to repeated sanding and are common in floors that reach the higher end of the refinish range.
• Softer woods, like pine, scratch and dent more easily during sanding and often call for a gentler starting grit even when the wood above the tongue is otherwise sufficient.
• Quarter-sawn boards can be denser and slower to sand than plain-sawn boards of the same species, which sometimes shows up as uneven drying time later if finish is applied unevenly across the room.

The short answer: A walk-through for loose boards, protruding fasteners, and squeaks saves problems mid-job.

• Protruding nail or staple heads can tear a sanding belt almost immediately, and a torn belt mid-pass wastes both material and time.
• Loose or squeaking boards tend to get worse under the vibration of a drum sander, worth resetting or securing before starting rather than discovering it partway through a room.
• Old wax, oil soap, or polish buildup can clog abrasives fast and may need a separate cleaning pass before the first sanding grit ever touches the floor.
• Gaps between boards from seasonal movement are normal and typically close up again once humidity levels even out; they’re rarely something to address before sanding.

Catching these on a walk-through before the first belt goes on the sander is faster than stopping mid-job to deal with a torn belt or a board that won’t stop rattling.

The short answer: Using a screen and recoat between full sands stretches out how long the floor’s total refinish budget actually lasts.

• A full sand removes wood and uses up one of the floor’s limited number of refinishes.
• A screen and recoat refresh the surface finish without removing any wood, so it doesn’t count against that total.
• A floor that gets a screen and recoat every few years, with a full sand only when the finish is truly worn through, can go decades longer between full refinishes than one that gets a full sand every single time the finish looks tired.

This is worth explaining to a customer directly, since a lot of homeowners assume every refinish means a full sand. In many cases, especially on a floor that’s still holding its finish reasonably well, a screen and recoat gets the same visual result for less cost and without spending down the floor’s remaining refinish life.

The short answer: The drum or belt sander does most of the work, but the edger needs to keep pace with it.

• A drum sander removes material faster and more evenly acrosan openen floor area than an edger does along the walls.
• If the edger runs a different number of passes at a different grit than the drum sander, the edges of the room can end up a shade different from the field once stain or finish goes down.
• Marking each grit change with a light pencil line before starting the next pass helps keep track of progress across a large room, since there’s no leftover finish to serve as a visual guide partway through the sequence.

Equipment built for this kind of full refinish work, like the Lagler Hummel Belt Sander or the American Sanders Legend 8″ Belt Sander, is built for the aggressive material removal a full-thickness solid wood floor can handle. That same equipment is too aggressive for a thin engineered wear layer, which calls for a gentler orbital or multidisc approach instead.

The short answer: Screening and recoating can still refresh the surface, but it won’t remove wood or fix damage that goes below the finish layer.

• A screen and recoat lightly abrades the existing finish so a new coat has something to grip, without removing any wood.
• It works well for surface dullness and light wear, but not for deep scratches, stains, or gouges in the wood itself.
• Once a floor is out of usable material above the tongue, replacement becomes the more honest option for anything a screen and recoat can’t fix.

The short answer: A floor near the end of its refinish life is a different conversation than one with plenty of material left.

• A floor with several refinishes still available can be quoted as a standard full sand and refinish without much hesitation.
• A floor close to the tongue-and-groove line may only support a screen and recoat safely, which changes both the scope and the price of the job.
• Bringing this up during the estimate, before any sanding starts, avoids a harder conversation later about why the job turned into something different than what was quoted

The short answer: Check the wood above the tongue, not the calendar or the number of times it’s already been done.

1. Find an exposed edge and check how much solid wood remains above the tongue-and-groove joint.
2. Confirm whether the floor is nail-down or glue-down, since that affects how much margin there is.
3. Run a 36-grit test patch in the worst section of the floor before committing to a starting grit.
4. Follow the grit sequence in order, without skipping more than one level.
5. Keep the drum sander and edger on matching grits and pass counts to avoid a visible mismatch at the walls.
6. If the floor is out of usable material, plan for a screen and recoat or replacement rather than forcing another full sand