The short answer: Check the manufacturer’s spec sheet first. Guessing from the surface is not reliable.

Where to actually find the number:

• Manufacturer spec sheets list wear layer thickness directly, usually in millimeters
• A cut edge at a heat register, vent cutout, or transition strip can show the layer in cross-section
• Some manufacturers stamp or print the spec on the box or the plank’s tongue

When there’s no spec sheet on hand:

• Pull a spare plank if one exists; closets and under large appliances sometimes have a leftover board from the original install
• A caliper on the tongue-and-groove edge shows the visible grain line where real wood ends and the core begins
• If the home has a basement or accessible crawlspace under a glued or nailed floor, a look from underneath at a seam or gap can sometimes confirm total board thickness, though not the wear layer specifically

Why you shouldn’t guess:

• A floor can look thick and substantial from above and still have a paper-thin veneer
• Finish sheen and board width tell you nothing about wear layer depth
• Sanding blind on an unconfirmed thickness is how a floor ends up sanded through into the core

The short answer: The listed wear layer thickness is often an average, not a guarantee at every point on the board.

What makes textured floors different:

• Hand-scraped and distressed boards have low points and dips built into the surface texture
• Those low points can sit thinner than the average thickness printed on the spec sheet
• A sander set to a “safe” depth for the average thickness can still break through in the low spots

What this means on the job:

• Most heavily textured engineered floors can only be lightly screened and recoated, not fully sanded
• If sanding is attempted anyway, expect visible core exposure at the low points before the rest of the floor is done
• When in doubt, a small test area in a closet or under a rug tells you more than the spec sheet does

The short answer: Something with more control and less aggressive material removal than a standard drum sander.

Better suited to engineered work:

• Mirka DEROS II 650X Orbital Sander: random orbital action, removes material more gradually and gives finer control near a thin veneer
• Bona Multidisc: multi-head design distributes the sanding pass more evenly across the floor

Better suited to solid wood or thick wear layers:

• Lagler Hummel Belt Sander: aggressive material removal, built for full sand-and-refinish jobs on solid wood
• American Sanders Legend 8″ Belt Sander: same category, same level of aggression

Running a belt sander meant for solid wood across a 2mm engineered wear layer is one of the fastest ways to sand straight through to the core.

The short answer: Screen and recoat instead of sanding.

What that process actually does:

• A screen (like 3M Screens) abrades the surface of the existing finish just enough to give a new coat something to grip
• No wood is removed, so it’s safe on wear layers too thin to sand
• It refreshes the sheen and fixes light surface wear, but it will not remove deep scratches, stains, or gouges that go into the wood itself

When a screen and recoat won’t work:

• The floor has wax, oil soap, or polish residue on it, which blocks the new coat from bonding properly
• Damage goes deeper than the finish layer, into the wood itself
• The floor has already been sanded down close to the core

If the floor doesn’t qualify for sanding and the damage is deeper than a screen-and-recoat can fix, replacement is usually the more honest answer than trying to force a refinish that won’t hold up.

The short answer: A quick order of operations to run through before committing to the job.

1. Confirm the wear layer thickness from the spec sheet, a spare plank, or a visible cross-section
2. Check whether the floor is textured or hand-scraped, and treat the listed thickness as a best case, not a guarantee, if it is
3. Confirm the installation method, floating, glued, or nailed, since that changes how the floor behaves under the sander
4. Run a test pass in a closet or under a rug before touching the rest of the room
5. Choose equipment based on what the test pass showed: an orbital or multidisc machine for anything on the thinner side and a standard drum or belt sander only once solid material is confirmed
6. Walk the customer through what the wear layer allows before the job starts, not after

Running through these six steps in order catches most of the problems that turn a routine refinish into a floor replacement halfway through the job.