For most standard interior plasterboard joints, you'll need three coats of stopping compound over your GIB tape — a bedding coat, a fill coat, and a finishing coat. Each coat has a specific job, and skipping one is the most common reason DIY plastering ends up showing through paint.
Why Three Coats?
Plasterboard stopping isn't just about hiding the tape — it's about building up a feathered, flat surface that blends invisibly with the surrounding board. Stopping compound shrinks slightly as it dries, so a single thick coat will crack or show a ridge. Three thin coats, each sanded lightly before the next, give you a stable, flat result.
GIB's technical literature outlines the recommended stopping system for their plasterboard products, and it consistently specifies a three-coat process for recessed (standard) joints.
The Three Coats Explained
Coat 1 — The Bedding Coat
This coat embeds the tape into the joint. Apply a thin layer of stopping compound into the recess, press your GIB tape firmly into it (paper tape is the trade standard), then skim a thin layer over the top to fully bed it in. The tape should be fully covered but the coat should be thin — you're not trying to fill the recess yet. Allow to dry completely (usually overnight in normal NZ conditions).
Coat 2 — The Fill Coat
Once the bedding coat is dry and lightly sanded, the fill coat builds up the recess to roughly flush with the board face. Feather the edges out wider than the first coat — typically 200–250 mm across the joint. This coat does most of the levelling work. Let it dry fully before sanding.
Coat 3 — The Finishing Coat
The finishing coat is a thin skim applied over a wider area (sometimes 300 mm or more) to blend the joint seamlessly into the board surface. Use a fine-grade finishing compound or a thinned-down version of your stopping compound. Sand lightly with 120–180 grit paper once dry, then prime before painting.
What About Butt Joints and External Corners?
- Butt joints (where two square-edged board ends meet) have no recess, so they need extra care. You may need to feather the stopping out even wider — up to 400 mm — and some plasterers apply a fourth coat to achieve a flat result.
- External corners use a metal or plastic corner bead, which is bedded in compound and then stopped over in two to three coats.
- Internal corners are taped with paper tape folded along the crease, then stopped in two to three coats.
Choosing the Right Stopping Compound
In New Zealand, you'll find two main types of stopping compound:
| Type | Best For | Notes |
|---|---|---|
| Premixed (air-dry) | DIY, small repairs, finishing coats | Shrinks more; longer dry time |
| Powder (setting-type) | Bedding coat, faster turnaround | Sets by chemical reaction; less shrinkage |
GIB recommends using their own system products for warranty purposes. You can also find compatible compounds from brands like Ardex and Mapei. Check with your supplier at Bunnings, Mitre 10, or PlaceMakers for what's available locally.
Drying Times in NZ Conditions
Drying times vary depending on your region's humidity and temperature. In Auckland's humid summers or on the West Coast, allow extra drying time between coats — rushing this is the number-one cause of cracking and poor adhesion. In dry Central Otago conditions, coats may dry faster. A coat that looks dry on the surface may still be damp underneath — check for any cool or dark patches before sanding.
Priming Before Painting
Once your final coat is sanded smooth, always apply a plasterboard primer before your topcoat. Stopped areas absorb paint differently to the board face, and skipping primer will leave shiny or patchy spots — especially visible in raking light. Resene, Dulux, and Wattyl all offer suitable plasterboard primers.
When to Call a Professional
Stopping is a skill that takes practice — even experienced DIYers often find their first few joints show up under paint. If you're working on a large area, a new build, or a renovation that requires a Level 4 or Level 5 finish (common where strong raking light is expected, such as near large windows), it's well worth engaging a qualified plasterer.
For work that forms part of a building consent — such as new partition walls or structural alterations — check with your local council whether the work needs to be carried out or inspected by a Licensed Building Practitioner (LBP). Plastering itself is not restricted electrical or plumbing work, but the broader building work it's part of may have consent requirements.
You can find qualified local plasterers on tradedirectory.co.nz to get the job done right first time.
Sources & Further Reading
- GIB — Plasterboard Systems & Technical Guides
- BRANZ — Build Magazine & Technical Guidance
- MBIE Building Performance — Building Code & Consent Info
- Licensed Building Practitioners — Find or Verify an LBP
- Resene — Primers & Paints for Plasterboard
- PlaceMakers — Stopping Compounds & Plastering Supplies
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