Prepping floorboards that have been glued with old adhesive is one of the trickier parts of a floor restoration project, but it's absolutely doable with the right approach. The key is removing as much adhesive as possible before you sand, because drum and belt sanders struggle badly with sticky residue — it clogs abrasives fast and can cause uneven results. Here's how to tackle it properly.
Stop First: Check for Asbestos
Before you touch anything, consider the age of your home. If your house was built before the mid-1980s, the old adhesive (or any vinyl tiles underneath) may contain asbestos. Disturbing asbestos-containing materials is a serious health hazard and is regulated under the Health and Safety at Work (Asbestos) Regulations 2016.
- If you're unsure, have a sample tested by a licensed asbestos assessor before proceeding.
- WorkSafe NZ has clear guidance on identifying and managing asbestos in homes.
- Do not sand, scrape, or grind suspect material until it has been cleared.
Identify the Type of Adhesive
Knowing what you're dealing with shapes your removal strategy. Common adhesives found on NZ floorboards include:
| Adhesive Type | Appearance | Typical Era | Removal Method |
|---|---|---|---|
| Bitumen (tar-based) | Black, tarry, brittle | Pre-1980s | Solvent or heat |
| Rubber/contact adhesive | Yellow-brown, rubbery | 1970s–1990s | Solvent or scraping |
| PVA/construction adhesive | White or cream, hard | 1990s–present | Mechanical scraping |
| Epoxy adhesive | Very hard, clear or amber | Any era | Mechanical grinding |
If you're not sure what type you have, take a small sample to your local flooring or hardware store for advice.
Tools and Materials You'll Need
- Floor scraper (long-handled, with replaceable blades)
- Heat gun (for softening stubborn adhesive)
- Oscillating multi-tool with scraper blade (great for tight spots)
- Adhesive remover/solvent suited to your adhesive type
- Mineral spirits or turpentine (for bitumen-based adhesives)
- Putty knife for detail work
- Safety gear: gloves, safety glasses, P2 respirator mask, knee pads
- Plenty of rags and a bucket
You can find most of these tools and consumables at Bunnings or Mitre 10.
Step-by-Step Adhesive Removal
1. Ventilate the Space
Open all windows and doors. Many adhesive solvents produce strong fumes. Wear your respirator and keep the area well ventilated throughout.
2. Apply Heat or Solvent
For bitumen or rubber adhesives, apply a suitable solvent or use a heat gun to soften the material. Work in small sections — about half a square metre at a time — so the adhesive doesn't re-harden before you scrape.
For hard construction adhesives, a heat gun alone often works well. Hold it 5–10 cm from the surface and move it slowly until the adhesive softens.
3. Scrape Methodically
Using your long-handled floor scraper, work at a low angle (roughly 20–30 degrees) and push firmly in the direction of the grain. Replace blades frequently — a dull blade tears the timber rather than shaving the adhesive cleanly.
4. Detail Work
Use a putty knife or oscillating multi-tool for edges, corners, and areas between boards. Take care not to gouge the timber.
5. Clean the Surface
Wipe down the floor with a rag dampened with the appropriate solvent to remove residue. Allow the floor to dry completely — typically 24 hours minimum — before sanding. Any remaining solvent or moisture will clog sandpaper and can affect your finish.
6. Inspect and Fill
Once clean, check for raised nails, damaged boards, and gaps. Punch nails at least 3 mm below the surface. Fill gaps and holes with a timber filler compatible with your intended finish. Products from Sika or similar brands are widely available and suitable for timber floors.
Sanding After Adhesive Removal
Even after thorough scraping, some adhesive residue usually remains. Start with a coarser grit than you'd normally use — typically 24 or 36 grit on a drum sander — to cut through the last of the residue and level the surface. Expect to go through more abrasive sheets than a standard sand job.
Tip: Always sand in the direction of the grain to avoid cross-grain scratches that show up under a clear finish.
For guidance on finishing products once your floor is prepped, Resene and Wattyl both offer NZ-formulated floor coatings with technical data sheets to help you choose the right product for your timber species and conditions.
When to Call a Professional
Some situations are best left to a qualified floor sanding professional:
- Confirmed or suspected asbestos — stop work immediately and contact a licensed asbestos removalist.
- Large areas of epoxy adhesive — this often requires specialist grinding equipment.
- Severely damaged or cupped boards — a professional can assess whether boards need replacing before sanding.
- Heritage or exotic timber — mistakes are costly and hard to reverse.
A licensed floor sanding tradesperson has the equipment and experience to handle difficult adhesive situations efficiently and safely. You can find qualified local floor sanders on tradedirectory.co.nz.
For broader guidance on building work and what requires consent, check MBIE Building Performance — floor sanding is generally exempt from building consent, but it's always worth confirming with your local council if you're unsure.
