Sanding right into floor corners and edges is the part most DIYers find hardest — and it's where uneven results show up most. The good news is that with the right tools, a bit of patience, and a logical sequence, you can get a consistent finish from the centre of the room all the way into the tightest corners.
Understanding the Three Zones of a Timber Floor
When sanding a timber floor, professionals break the job into three zones:
- Field – the main open area, sanded with a large drum or belt sander
- Edges – the strip running 100–200 mm around the perimeter, where the drum sander can't reach
- Corners – the very ends of each edge run, where even an edge sander won't fit
Each zone needs a different tool and technique. Skipping or rushing any zone leaves visible lines and patchy staining.
Tools You'll Need
| Zone | Tool | Hire or Buy? |
|---|---|---|
| Field | Drum or belt floor sander | Hire |
| Edges | Rotary edge sander | Hire |
| Corners | Detail/triangle orbital sander or hand scraper | Buy or hire |
| Tight spots | Carbide hand scraper | Buy |
Hire equipment is available from most tool hire shops around NZ. Ask specifically for a rotary edge sander (sometimes called a disc edger) — it's a dedicated machine that gets within about 10–15 mm of the skirting board.
Sanding the Edges
The rotary edge sander is a powerful, fast-cutting machine. Treat it with respect:
- Start with the same grit you're using on the field (often 40 or 60 grit for a first cut on rough floors).
- Work in a sweeping arc motion — never hold the machine still or it will dig a circular gouge into the timber.
- Keep the machine moving constantly, overlapping each arc by about a third.
- Work along the grain direction as much as possible on your finer grits (80 and 100+).
- Feather the edge zone into the field zone so there's no visible line between them. This is the most common mistake — check by crouching low and looking along the floor in raking light.
Grit sequence for edges: Match the field — typically 40 → 60 → 80 → 100 (or 120 for a finer finish). Don't skip grits.
Tackling the Corners
This is where a rotary edger simply can't reach. You have a few options:
Detail orbital sander (triangle or multi-tool)
A triangular detail sander (sometimes called a delta sander) fits into 90-degree corners reasonably well. Use the same grit progression as the rest of the floor. These are inexpensive to buy and widely available at Bunnings or Mitre 10.
Oscillating multi-tool with sanding pad
An oscillating multi-tool fitted with a triangular sanding pad is excellent for corners. The rapid oscillation removes material efficiently without the swirl marks a rotary tool can leave.
Hand scraper
A carbide hand scraper is the traditional method and still one of the best. Hold it at roughly 45–75 degrees to the floor and push or pull firmly along the grain. It takes a bit of practice but gives excellent control right into the corner. Sharpen or replace the blade when it stops cutting cleanly.
Sanding by hand
For the very last grit (100 or 120), wrapping sandpaper around a small block and working by hand along the grain gives a clean, consistent result in corners that matches the rest of the floor.
Getting a Consistent Finish
- Always check your work in raking light (a torch held low and parallel to the floor) before moving to the next grit. Scratches from coarser grits must be fully removed before you go finer.
- Vacuum thoroughly between every grit change — dust from coarser paper left on the floor will scratch your finer finish.
- The goal is for the corner and edge zones to look identical to the field when the coating goes on. Stain will highlight any inconsistency dramatically.
- If you're applying a penetrating oil (like a Rubio or similar product), the surface prep is especially critical as these finishes don't fill scratches the way polyurethane can.
Dust and Safety
Floor sanding generates large volumes of fine dust. WorkSafe NZ classifies fine wood dust as a health hazard with repeated exposure.
- Wear a P2-rated dust mask at minimum — not a basic paper mask.
- Seal off doorways to the rest of the house with plastic sheeting.
- Hire sanders with dust bags and empty them regularly.
- Keep the work area ventilated.
- Sanding dust is flammable — no open flames, pilot lights, or smoking near the work area. Empty dust bags outside away from the house.
When to Call a Professional
Floor sanding is satisfying DIY work, but there are situations where a professional floor sander is the better call:
- Parquet, herringbone, or diagonal-laid floors — these require sanding at specific angles and are easy to ruin.
- Thin overlay floors — if the boards are thin or have been sanded multiple times before, a professional can assess whether there's enough timber left.
- Large areas or tight timelines — professionals work significantly faster and get a more consistent result.
- Floors with significant damage, cupping, or movement — these may need assessment before sanding.
You can find qualified local floor sanding professionals on tradedirectory.co.nz.
