Equipment Care & Repair

Sanding Wood Floors: Machines and Grit Sequence

Sanding angles, grit sequences, drum and edger technique, and dust, fire and lead rules for sanding wood floors, from Lägler, Bona, NWFA and EPA.

Updated · 3 min read

Sanding is about removing the last grit's scratches with the next one. Start with the finest grit that will do the job, don't skip more than one grit, and cut at an angle until the last pass. The details below come from sander makers' manuals and NWFA.[1][2][3][4] Follow the manual for your machine.

Fire, dust and lead

Sanding dust can ignite. Empty the dust bag when it's a third full,[3] and always take it off the machine and empty it outdoors into a non-flammable container.[1] Hitting a nail can spark a fire, so sink every nail first. In pre-1978 homes, the finish may count as a painted surface under EPA's lead rule, and sanding it requires shrouded machines with HEPA collection.[5] Wood dust can cause respiratory problems and cancer, according to OSHA.[6][7]

Before you start

Prep decides how many passes you need.

  • Countersink every nail and screw deep enough that the sander can't reach them.[1]
  • Vacuum the floor and the expansion gaps right before sanding.[1]
  • Always check moisture on a cupped floor before sanding it.[1] See Wood acclimation and moisture.
  • Joints wider than about 1/32" can't be closed permanently with filler.[1]

Grit sequence

Each grit removes the scratch from the one before it.

  • Start with the finest grit that will do the job.[1] Do a test pass first.
  • For strip and plank on a belt sander, skip no more than one grit. For fine sanding, skip none.[1]
  • End grain is stricter: don't skip any grits.[4]
Step (Bona example)[2] Grit Machine
Coarse 40 to 50 Belt or drum sander
Medium 60 to 80 Belt or drum sander
Edges 60 to 80 Edger
Fine 100 to 120 Multi-disc sander

A badly damaged or uneven floor may need a coarser start.

Angle and direction

Angle cuts level the floor; the last cut goes with the grain.

  • On strip and plank, sand every step except the last at 15 to 45 degrees to the grain, then make the last pass with the grain.[1] The more uneven the floor, the greater the angle.
  • Parquet and herringbone: 45 degrees.[1] End grain: first cut at 45°, second on the opposite 45°.[4]
  • On cupped boards with large height differences, even them out with the grain first.[1]

Running the big machine

Most drum marks come from technique.

  1. Work left to right so the left wheel rides on freshly sanded floor.[1]
  2. Lower the drum while moving forward and lift it before stopping. Never pause while lowering or raising the drum, and keep a steady pace.[3]
  3. Overlap each pass by about half the drum width.
  4. Reduce pressure and walk faster as the grits get finer.
  5. Vacuum between grits.

Edges and corners

The edger has to match the field.

  • Use the same grit on the edger as on the big machine for each step, including the final cut.[1][4] Hand-scrape corners and around jambs.
  • Don't sharpen scrapers over raw wood when using waterborne finish; the filings can cause rust or black spots.[4]

Dust collection

A HEPA vacuum at the machine controls dust and, on pre-1978 finishes, is required. EPA defines HEPA as capturing 99.97% of particles at 0.3 microns.[8] Pulse-Bac PRO Series vacuums meet that rating.[9] The American Sanders EZ-8 accepts a remote vacuum on a 2" or 1.5" hose.[3]

Common mistakes

These leave marks you'll see under finish.

  • Starting too coarse. You spend the next two grits removing the damage.
  • Skipping grits. Scratches show through the finish.
  • Stopping with the drum down. It gouges the floor in one spot.
  • Different grits on edger and field. The perimeter looks different.
  • Leaving a full dust bag. It's a fire risk.

Dust collection we carry

We don't sell sanders, but these vacuums and hoses work with them.

Regulations and references

  1. Lägler: Sanding of wooden floors, the manual
  2. Bona: Sanding sequence
  3. American Sanders EZ-8 operator's manual
  4. NWFA: Sanding end-grain flooring
  5. EPA Lead RRP rule, 40 CFR 745.85 (work practices)
  6. OSHA: Wood dust
  7. NIOSH Pocket Guide: Wood dust
  8. EPA Lead RRP rule, 40 CFR 745.83 (definitions)
  9. Pulse-Bac: PRO Series vacuums

Linked PDF documents are archived copies saved by PreFloor Tools so they stay available if the publisher moves or removes them. Check the publisher's website for the latest revision.

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