You can use a floor polisher to buff between coats of polyurethane, but it needs to be set up correctly — wrong pads or too much pressure can scratch, scuff, or even cut through the coat you've just applied. Done right, light buffing between coats improves adhesion and gives you a noticeably smoother final finish.
Why Buff Between Coats at All?
Each coat of polyurethane, as it dries, can raise tiny fibres in the timber grain and leave a slightly rough or "whiskery" surface. Buffing — also called intercoat abrading or scuff sanding — knocks back these nibs without removing the coat itself. The result is better mechanical adhesion for the next coat and a flatter, more even sheen in the end.
This step is standard practice for professional floor sanders and is recommended by most polyurethane manufacturers. Check the technical data sheet for the specific product you're using, as cure times and recommended abrasive grits can vary.
Floor Polisher vs. Orbital Sander: What's the Difference?
A floor polisher (sometimes called a buffer or swing machine) spins a large disc at relatively low RPM. It covers ground quickly and is well suited to light abrading between coats. A random orbital floor sander is more aggressive and is better suited to cutting back bare timber or removing old finishes.
For intercoat buffing, the floor polisher is often the preferred tool because:
- It's gentler and less likely to cut through a thin coat
- It covers large areas evenly
- It's widely available for hire from tool hire shops around NZ
Choosing the Right Pad and Grit
This is where most DIYers go wrong. Using the wrong abrasive is the most common cause of scratched or dulled finishes.
| Situation | Recommended abrasive |
|---|---|
| Between first and second coat (water-based poly) | 180–220 grit screen disc or maroon abrasive pad |
| Between coats (oil-based poly) | 120–180 grit screen disc |
| Final light denib before last coat | 220 grit screen or white nylon pad |
| Polishing after final coat (fully cured) | White or red polishing pad — no abrasive |
Screen discs (mesh abrasive discs) are the most common choice for intercoat abrading with a floor polisher. They attach under a drive pad and are available from floor sanding suppliers and most large hardware stores.
Avoid steel wool — it can leave fine metal particles that rust under the finish and cause dark spots in your floor.
Step-by-Step: Buffing Between Coats
- Wait for the coat to fully dry — not just touch-dry. Check the manufacturer's recoat window on the tin. Water-based polyurethanes often allow recoating within 2–4 hours; oil-based products may need 12–24 hours or more. Buffing too early will gum up the pad and damage the coat.
- Vacuum and tack the floor — remove all dust before you start.
- Fit the correct screen disc or pad to the floor polisher's drive pad.
- Work in the direction of the grain where possible, using smooth, overlapping passes. Don't linger in one spot.
- Check your work — the sheen should look uniformly dull ("scuffed"). Any shiny patches mean you've missed a spot; any bare timber showing means you've cut through and will need to recoat carefully.
- Vacuum thoroughly, then wipe down with a tack cloth or a slightly damp microfibre cloth (for water-based products). Let it dry completely before applying the next coat.
Common Mistakes to Avoid
- Buffing too soon — the coat isn't hard enough and you'll create a mess
- Using too coarse a grit — you'll leave visible scratch marks in the finish
- Skipping the vacuum step — sanding dust trapped under the next coat creates a gritty surface
- Applying too much pressure — let the machine do the work; pressing down hard increases the risk of cutting through
- Buffing the final coat — unless you're using a very fine polishing pad on a fully cured floor, leave the last coat alone
NZ Climate Considerations
NZ's humidity levels vary significantly by region and season, and this affects drying times. In humid conditions (common in Auckland and Northland), water-based polyurethanes can take longer to dry than the tin suggests. In cold South Island winters, oil-based products can be very slow to cure. Always check the actual dryness of the coat — press a fingernail gently in an inconspicuous spot — before buffing. BRANZ has useful guidance on how moisture and temperature affect timber floor coatings.
Hiring Equipment
Floor polishers are readily available for daily or weekend hire from most tool hire outlets. Make sure you ask specifically for a buffing/polishing machine rather than a drum sander or edger, which are much more aggressive. Hire shops can also advise on the correct screen disc grit for your product.
For supplies and finishing products, Bunnings, Mitre 10, and PlaceMakers stock a range of polyurethane coatings and abrasive accessories.
When to Call a Professional
Floor finishing is a skill that takes practice. If your floor has deep scratches, significant staining, or an old finish that needs stripping, the job moves beyond intercoat buffing into full sanding — which involves drum sanders and edgers that can cause serious, expensive damage in inexperienced hands.
If you're unsure about any stage of the process, or if you want a guaranteed result on a valuable timber floor, it's well worth engaging a qualified floor sanding professional. You can find licensed, reviewed floor sanders in your area on tradedirectory.co.nz.
Safety note: Polyurethane products — especially oil-based — produce flammable vapours. Ensure the area is well ventilated, keep ignition sources away, and dispose of used rags safely (oil-soaked rags can self-ignite). Check the product's safety data sheet and refer to WorkSafe NZ for guidance on safe handling of finishing products.
