Floor Sanding Abrasive Grit Guide: Which Grit for Each Stage?

Selecting the right sanding abrasive grit sequence is critical to achieving a smooth, professional timber floor finish. Use the wrong grit at the wrong stage and you create scratches that show through your oil or lacquer. This guide explains each grit level, when to use it, and which abrasive types work best for Australian hardwoods and softwoods.

How Grit Numbers Work

Grit numbers refer to the size of the abrasive particles on the disc, belt or paper. Lower numbers mean coarser, more aggressive cutting. Higher numbers mean finer, smoother finishing. A 24-grit disc removes material fast. A 150-grit disc creates a smooth surface ready for coating.

The standard sanding sequence moves from coarse to fine in controlled steps. Skipping grits or jumping too far between stages leaves visible scratch patterns in the finished floor.

Coarse Grits: 16 to 40

Use coarse grits for the initial cut. This stage removes old coatings, levels uneven boards and takes the floor down to fresh timber. A 24-grit or 36-grit ceramic or zirconia belt on a drum sander handles this work efficiently.

Ceramic abrasives from SIA cut faster and last longer than standard aluminium oxide at this stage. They handle the heat generated during heavy material removal without glazing over.

Run the sander with the grain. Diagonal passes are acceptable on the first cut to level cupped boards, but follow up with a pass along the grain direction.

Medium Grits: 60 to 80

The medium grit stage removes the scratch pattern left by the coarse grit. A 60-grit pass followed by an 80-grit pass is the standard approach. This is where the floor starts to look smooth.

Zirconia abrasives perform well at this stage. They maintain their cutting edge longer than aluminium oxide and produce consistent results across the floor.

Pay attention to the edger work. Match the grit sequence on the edger to the drum sander. If you finish the main floor at 80 grit, the edges need to match before moving to fine grits.

Fine Grits: 100 to 150

Fine grits prepare the timber for coating. A 100-grit or 120-grit pass removes the medium grit scratch pattern and creates a surface smooth enough for oil or lacquer application.

For water-based lacquer systems like Berger-Seidle AquaSeal, finish at 120 grit. Water-based products highlight fine scratches, so the surface needs to be clean and consistent.

For oil finishes like Rubio Monocoat or WOCA, 100 to 120 grit works well. Going too fine with oil finishes reduces absorption. The timber needs some tooth for the oil to grip.

Abrasive Types Explained

Aluminium Oxide: The most common abrasive. Good all-round performance. Cost-effective for fine grit work and general sanding.

Zirconia: Harder than aluminium oxide. Self-sharpening as it wears. Ideal for medium grits and hardwood species like spotted gum, blackbutt and jarrah.

Ceramic: The hardest and longest-lasting option. Best for coarse grit work and heavy material removal. SIA ceramic discs and belts are the professional standard in Australia.

Disc, Belt or Paper?

Drum sanders use belts for the main floor area. Edgers use discs. Orbital or multi-disc machines use paper or mesh pads for the final screening pass.

Match the abrasive type to the machine and the stage. Ceramic belts on the drum for the first cut. Zirconia discs on the edger for medium work. Aluminium oxide mesh on the buffer for the final screen.

Common Sanding Mistakes

Skipping grits. Jumping from 36 straight to 100 leaves deep scratches that the fine grit cannot remove. Follow the sequence: 36, 60, 80, 100 or 120.

Using worn abrasives too long. A dull disc generates heat, burns the timber and creates an uneven surface. Change abrasives when they stop cutting efficiently.

Ignoring the edges. The edger needs the same grit progression as the drum sander. Mismatched edges show clearly once the finish is applied.

Recommended Grit Sequence

For most Australian hardwood floors, this sequence delivers professional results:

First pass: 24 or 36 grit (ceramic belt on drum sander)
Second pass: 60 grit (zirconia belt on drum sander)
Third pass: 80 grit (zirconia or aluminium oxide)
Fourth pass: 100 or 120 grit (aluminium oxide)
Final screen: 120 or 150 grit (mesh pad on buffer)

EcoGrit stocks the full range of SIA professional sanding abrasives including ceramic, zirconia and aluminium oxide discs, belts and papers. Browse the Abrasives collection to find what you need for your next job.