How to Sand a Timber Floor
Step-by-step guide to sanding and finishing a timber floor with the Bona system. Watch a real job from start to finish.
Sanding and refinishing a cypress pine floor with Bona Traffic HD Extra Matt. Products supplied by Sand-Aid. Thanks to Sap & Grain for sharing their work with the trade.
Watch with captions on YouTube →
Before you start
The video shows Sap & Grain Timber Flooring working through a cypress pine floor -- a relatively soft, knotty Australian species with a warm honey colour. The same process applies to any timber species; the only things that change per species are the starting grit, the primer choice, and how hard the belt has to work.
- Clear the room. All furniture out. Remove shoe moulding and quarter-round if fitted.
- Check for fasteners. Walk the floor and hammer down any protruding nails, pull staples, check for screws flush with the surface. A belt sander hitting a nail destroys the belt and scores the drum.
- Seal doorways. Tape plastic sheeting over doorways to contain dust. Even with Bona DCS extraction, fine particles travel.
- Check the moisture content. Pin-test the timber. If it's above 14% MC, the floor isn't ready to sand. Full moisture guide here.
Step 1: Belt sand the field
1The belt sander does the heavy lifting. Run it along the board direction (never across the grain on a straight-laid floor). Start at the grit the species and condition call for -- on the cypress pine in the video, that's P40 or P50 since cypress is soft and forgiving.
Work through the full grit sequence without skipping:
- Cypress pine: P40 → P60 → P80 → P100
- Blackbutt / spotted gum: P40 → P50 → P60 → P80 → P100
- Ironbark: P36 → P40 → P60 → P80 → P100
The grit sequence picker gives the exact sequence for any species, condition, and finish. Sand-Aid stocks SIA 2800 Siaron Zirconia belts in 200x750mm and 250x750mm, P24 through P120.
Step 2: Edge the perimeter
2The edger reaches where the belt sander can't -- the perimeter, under kickboards, around doorframes, and into corners. Match the edger to the same grit as the belt or step one finer (e.g. if the belt finished at P100, run the edger to P120). The edger cuts in a circular pattern, which is why the picture framing guide exists -- blending the two zones later is critical.
Step 3: Inspect under raking light
3This is the step most beginners skip and most callbacks come from. Hold a torch flat against the floor so the light rakes across the surface at a shallow angle. Walk every section. Look for:
- Drum marks -- straight lines following the sanding direction. Caused by a worn belt or too much pressure.
- Edger swirls -- circular arcs around the perimeter. Caused by a coarse edger disc or uneven pressure.
- Cross-grain scratches -- diagonal marks where the sander ran at an angle to the boards.
If you see any of these: go back a grit and re-sand the affected area. Finding them now costs 30 minutes. Finding them after the topcoat costs a full re-sand. Full sanding marks guide here.
Step 4: Buffer the whole floor
4Run a Bona FlexiSand 1.9 buffer with a fine screen or maroon pad over the entire floor -- field and edges. This does two things: it levels out the scratch pattern difference between belt and edger (preventing picture framing), and it opens the grain for the primer to absorb evenly.
Step 5: Vacuum and clean
5Vacuum the floor. Then vacuum the walls, window sills, ledges, and every horizontal surface above the floor -- because dust settled on those surfaces will fall into the wet coating. Wipe down with a tack cloth. Turn off the HVAC so the air system doesn't circulate dust back into the room. Change clothes if needed. Full dust control guide here.
Step 6: Prime
6Apply one coat of primer with a roller or T-bar at about 8 m² per litre.
- Cypress pine: Bona Classic UX -- low tannin, no bleed risk. Keeps the warm honey colour.
- Blackbutt, tallowwood, spotted gum, ironbark: Bona Prime Intense -- controls tannin bleed and pops the grain colour.
The primer picker tells you exactly which primer for any species and finish goal. Allow 1-2 hours drying before the next step.
Step 7: Intercoat abrade
7Light pass with a maroon pad on the buffer after the primer dries. This knocks back any dust nibs that landed in the wet primer and keys the surface for the topcoat. Takes 10-15 minutes per room.
Step 8: First topcoat
8In the video, Sap & Grain apply Bona Traffic HD in Extra Matt -- the closest water-based finish to a raw-timber look, at just 10% gloss. Roll or T-bar at 8-10 m² per litre. Allow 2-3 hours drying before the next coat.
The topcoat options and when to pick each:
- Bona Traffic HD -- 2K commercial benchmark. Satin, Matt, Extra Matt. For high-traffic and commercial.
- Bona Traffic GO -- 1K with built-in hardener. Same sheens, no mixing, no pot life.
- Bona Mega -- 1K with oxygen cross-linking. The residential default. Gloss, Satin, Matt, Extra Matt.
- Bona Wave 2K -- 2K at a residential price. Silkmatt, Matt.
- Handley Urethane -- traditional solvent poly in 20L trade packs. Gloss, Satin, Low Sheen, Matt.
The coverage calculator gives the exact litres and pack sizes for any product and floor area.
Step 9: Second topcoat
9Intercoat abrade again (maroon pad), then apply the second coat the same way. Walk-on traffic in 24 hours for Bona Traffic HD. Full cure over the following 3-7 days depending on the product. Keep furniture off for at least 3 days.
The species in the video: cypress pine
Cypress pine is one of the softer Australian timbers (Janka hardness ~6.5 kN). It sands quickly, takes primer and topcoat well, and doesn't have the tannin issues of blackbutt or spotted gum. The warm honey colour with dark knots is part of its character -- most clients want the knots visible, not hidden. Classic UX is the right primer (no tannin control needed), and any Bona topcoat works well on top. Sand finer around the knots to avoid tearing the softer grain around them.
Blackbutt, spotted gum, ironbark, jarrah, and Tasmanian oak each have their own species guide with the specific grit sequence, primer, and topcoat recommendations.
Products used in this job
- Bona Traffic HD Extra Matt -- the topcoat
- Bona Classic UX -- the primer (cypress pine is low-tannin)
- SIA 2800 Siaron Zirconia belts -- the abrasives
- SIA abrasive discs -- for the edger
All supplied by Sand-Aid, Toronto NSW. 1300 950 551.
Sap & Grain are a professional floor sanding contractor running the full Bona system. The video above shows their real work on a real floor -- not a studio demo. Products supplied by Sand-Aid. Follow Sap & Grain on YouTube for more of their floor sanding work.
Sanding a floor this week?
Ring with the species, the square metres, and the condition. You'll get the grit sequence, the primer, the topcoat, the litres, and the schedule in one call.
Call 1300 950 551