Sanding a floor covered in multiple thick layers of paint is one of the more demanding DIY floor projects you can take on. The paint clogs abrasives quickly, can hide the true condition of the timber underneath, and may contain hazardous materials like lead. With the right preparation, equipment, and approach, however, it is absolutely achievable — and the results can be stunning.
Test for Lead Paint First
Before you touch a sander, this step is non-negotiable. Homes built before 1980 in New Zealand commonly used lead-based paints, and sanding lead paint creates fine dust that is a serious health hazard. Purchase a lead paint test kit from a hardware store (available at Bunnings or Mitre 10) and test the paint layers before starting.
If lead is detected, you have two options:
- Hire a specialist trained in lead paint removal — this is strongly recommended for thick, multi-layer situations.
- If you proceed yourself, follow WorkSafe NZ guidelines for working with hazardous substances, including wearing a P2 respirator (not just a dust mask), disposable coveralls, and sealing off the work area completely.
Dispose of lead-contaminated dust and debris as hazardous waste through your local council.
Gather the Right Equipment
Regular sanding sheets will clog and burn out within minutes on thick paint. You need:
- Drum sander or belt sander (hire) — a large drum sander is the workhorse for open floor areas. Hire one from a tool hire company or a flooring specialist.
- Edge sander — for the perimeter the drum sander can't reach.
- Detail sander or hand scraper — for corners and tight spots.
- Open-coat abrasives — these are specifically designed to resist clogging on paint and soft materials. Start with a coarse grit (16–24 grit) for the initial paint removal passes.
- Dust extraction — most hire sanders have a built-in bag, but connect to a vacuum where possible and seal doorways with plastic sheeting.
- P2 respirator, safety glasses, and hearing protection — essential.
Prepare the Room
- Remove all furniture, rugs, and fittings.
- Punch any raised nail heads below the surface with a nail punch — exposed nails will shred your abrasive paper instantly.
- Check for loose boards and screw or nail them down.
- Seal gaps under doors and cover air vents to contain dust.
- Open windows for ventilation, but be mindful of dust spreading to neighbouring areas.
The Sanding Process: Step by Step
Pass 1 — Coarse Grit (Paint Removal)
Load the drum sander with 16 or 24 grit open-coat paper. Work at a 45-degree angle to the grain on the first pass if the paint is very thick — this is more aggressive and lifts paint faster. Keep the machine moving at all times; stopping with the drum spinning will gouge the timber.
Expect to change abrasive sheets frequently — thick paint is brutal on paper. Have plenty of spares on hand.
Pass 2 — Medium Grit (Levelling)
Once the bulk of the paint is gone, switch to 40 grit and work parallel to the grain. This pass removes the scratch marks from the coarse grit and begins to level the surface.
Pass 3 — Fine Grit (Finishing)
Finish with 60–80 grit to smooth the surface ready for your chosen finish. Some floors may benefit from a final 100 grit pass if you want a very smooth result.
Use the edge sander at each grit stage to match the main floor, and finish corners by hand with a scraper or detail sander.
Checking Your Progress
| Grit | Purpose | Direction |
|---|---|---|
| 16–24 | Remove thick paint | 45° to grain |
| 40 | Level and blend | With grain |
| 60–80 | Smooth finish | With grain |
| 100 (optional) | Ultra-smooth | With grain |
Dealing with Stubborn Paint in Corners and Edges
Paint often builds up thickest in corners and along skirting boards. A heat gun can soften thick paint for scraping before you sand — this reduces clogging and makes the edge sander's job much easier. Work carefully with a heat gun near timber to avoid scorching.
Finishing the Floor
Once bare timber is exposed and the surface is smooth, vacuum thoroughly and wipe down with a tack cloth before applying your chosen finish. Options include polyurethane, hard-wax oil, or water-based floor coatings. Products from Resene, Dulux, and Wattyl all offer floor-specific finishes suited to NZ conditions. Always follow the manufacturer's application instructions and allow proper drying time between coats.
When to Call a Professional
Consider hiring a qualified floor sanding professional if:
- Lead paint is confirmed — specialist removal is the safest option.
- The floor has severe damage, deep gouges, or cupping that needs assessment before sanding.
- You are unsure about the timber species or thickness — some older NZ floors have thin wear layers that can be sanded through if you're not experienced.
- The job is large or time-sensitive — professionals have commercial-grade equipment that works significantly faster.
A licensed floor sander will also know how to assess whether a floor is worth saving or needs replacement. You can find experienced local floor sanding professionals on tradedirectory.co.nz.
For guidance on building work and what requires consent, check MBIE Building Performance — floor sanding generally does not require a building consent, but it's always worth confirming with your local council if you're unsure.
