Stopping, skimming and rendering are all plastering techniques, but they serve very different purposes and are applied to different surfaces. Understanding the difference helps you describe the job accurately when getting quotes — and ensures you hire the right tradesperson for the work.
Stopping: Finishing Plasterboard Joints and Holes
Stopping (sometimes called jointing) is the process of filling and smoothing the joints, screw holes, and imperfections in plasterboard (GIB board) walls and ceilings before painting. It's the most common plastering task in NZ new builds and renovations, since the vast majority of interior walls are lined with GIB plasterboard.
The process typically involves:
- Embedding paper or fibreglass tape over board joints
- Applying stopping compound (also called joint compound or filler) in multiple coats
- Sanding back between coats to achieve a flat, seamless surface
- Finishing to a Level 3, 4 or 5 finish depending on the paint sheen and lighting conditions
GIB publishes detailed guidance on stopping levels and recommended compounds for their board systems — it's worth checking if you're specifying finish quality for a project.
Stopping is generally considered non-restricted work, meaning a competent homeowner can patch small holes or touch up minor damage. However, achieving a truly flat, paint-ready finish across large areas takes skill and practice, and poor stopping is very obvious once paint goes on — especially with low-sheen or gloss paints.
Skimming: A Thin Plaster Coat Over an Existing Surface
Skimming refers to applying a very thin finishing coat of plaster — typically 2–4 mm — over an existing surface to create a smooth, even base for painting. It's often used to:
- Refresh old, rough or damaged plaster walls
- Smooth over textured surfaces (like orange peel or stipple ceilings)
- Cover repaired areas where the texture no longer matches
- Provide a high-quality finish over plasterboard that has already been stopped
Skimming uses a fine-finish plaster or a proprietary finishing compound, applied with a steel trowel and feathered out to a very thin, consistent layer. It requires a high level of skill to avoid trowel marks, ridges or uneven thickness — this is where experienced plasterers really earn their keep.
In NZ, skimming is commonly used when renovating older homes with fibrous plaster or hard plaster walls, which may have cracked or deteriorated over time. It can also be applied over plasterboard to achieve a superior Level 5 finish for high-gloss paints or feature walls.
Rendering: External (and Sometimes Internal) Cement or Plaster Coatings
Rendering is the application of a cement-, lime- or acrylic-based coating to exterior walls — or occasionally internal masonry walls. It's a much thicker application than skimming, typically 10–20 mm, and is used to:
- Weatherproof and protect exterior masonry, brick or block walls
- Provide a decorative finish on fibre cement or polystyrene cladding systems
- Cover and seal exterior substrates before painting or texture coating
- Achieve a specific architectural look (e.g. smooth, textured or patterned finishes)
In NZ, rendering is closely tied to the NZ Building Code — particularly Clause E2 (External Moisture). Exterior render systems must be correctly detailed to prevent water ingress, and many proprietary systems (such as those using James Hardie fibre cement substrates) require the render to be applied strictly to the manufacturer's specifications to maintain warranty and Code compliance.
Render mixes vary widely:
| Type | Common Use | Key Characteristic |
|---|---|---|
| Cement render | Masonry, block, brick | Hard, durable, traditional |
| Acrylic render | Lightweight cladding systems | Flexible, crack-resistant |
| Lime render | Heritage/older homes | Breathable, softer finish |
| Polymer-modified | High-performance exterior | Improved adhesion and flexibility |
Products from Sika and Ardex are commonly used by NZ plasterers for render and finishing systems.
Key Differences at a Glance
- Stopping = filling joints and holes in plasterboard — interior, thin, paint prep
- Skimming = thin finishing coat over an existing surface — interior (usually), smoothing and levelling
- Rendering = thick protective/decorative coat — exterior (mainly), weatherproofing and finish
Do You Need a Building Consent?
Most interior stopping and skimming work does not require a building consent. However, if you're re-cladding or significantly altering an exterior wall system, a building consent is very likely required. Always check with your local council before starting exterior work — MBIE Building Performance has useful guidance on what triggers consent requirements and Schedule 1 exemptions.
When to Call a Professional
While patching a small hole in GIB is a reasonable DIY job, most plastering work benefits enormously from professional skill:
- Large stopping or skimming jobs — uneven or ridged surfaces are very hard to fix once painted
- Any exterior rendering — incorrect application can lead to water damage, Code non-compliance and costly remediation
- Heritage or hard plaster walls — matching existing texture and composition requires specialist knowledge
- New builds or major renovations — a Licensed Building Practitioner (LBP) may be required to carry out or supervise certain restricted building work
A qualified plasterer will assess your substrate, recommend the right system, and deliver a finish that holds up over time. You can find experienced local plasterers on tradedirectory.co.nz.
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