The Australian and New Zealand standard for plasterboard, AS/NZS 2589, defines three main levels of finish. Level 4 is the default for most painted walls and ceilings. Level 5 adds a thin skim coat over the whole surface and is the right choice where light hits walls at a low angle, or where you're using gloss paint or dark colours. Paint can't turn a Level 4 wall into a Level 5 wall, so the finish level needs to be decided before the plastering starts.
Have you ever looked at a freshly painted wall at night and thought it was perfect, then seen it in the late afternoon sun and noticed faint lines, ripples and patches? You're not imagining it, and it doesn't always mean the work was done badly. It usually comes down to two things: the level of finish that was specified, and the lighting in the room.
What are levels of finish?
Levels of finish are a set of guidelines in AS/NZS 2589, the standard for applying and finishing gypsum linings like plasterboard. They describe how much jointing, coating and sanding is done before painting, and what quality you can expect from the result.
The standard covers several levels, but three matter for most homes and offices:
| Level | What's involved | Where it suits |
|---|---|---|
| Level 3 | Joints and fixings set and coated, but not to a smooth paint-ready standard | Areas with heavy textured finishes or that won't be decorated, such as garages, service areas and above suspended ceilings |
| Level 4 | Joints, corners and fixings fully set, coated and sanded smooth | The default for most painted walls and ceilings with flat or low-sheen paint and normal lighting |
| Level 5 | Level 4, plus a thin skim coat applied over the entire surface | Critical lighting, gloss or semi-gloss paint, dark colours and feature walls |
Unless something else is specified, Level 4 is the default for plasterboard that will be painted.
Why a Level 4 wall can still show joints
Plasterboard has a paper face. The joints and screw holes are covered with plaster compound. Even when they're sanded perfectly flat, paper and plaster absorb paint differently and have slightly different textures. Joints can also have a very gentle crown that's impossible to see straight on.
Under soft, even light, none of this shows. But when light skims across the surface at a low angle, every tiny difference casts a shadow. This is where Level 5 comes in. The skim coat over the whole board evens out the surface and texture, so there's no difference between paper and joint for the light to pick up.
What is critical lighting?
Critical lighting is light that hits a wall or ceiling at a low, glancing angle, nearly parallel to the surface. It's the enemy of a flawless finish. Common examples in Sydney homes include:
- Large windows and glass doors that let low morning or afternoon sun rake along a wall
- Skylights shining down a wall
- Downlights close to a wall, especially wall-washer lighting
- LED strip lighting in bulkheads, coves and shadowline ceilings
- Long hallways and high ceilings, where light travels along large uninterrupted surfaces
Modern open-plan homes with big windows and lots of LED lighting have far more critical lighting than older homes, which is one reason this issue is more noticeable today.
Paint choices matter too
Paint can make imperfections more or less visible:
- Gloss and semi-gloss reflect more light and highlight every flaw.
- Dark colours show surface variation more than light colours.
- Flat and matte finishes are the most forgiving.
One important point: a good paint job can't upgrade the finish level. Extra coats of paint won't hide joints under critical lighting if the plasterboard underneath is a Level 4 finish. If you want semi-gloss walls or a dark feature wall, plan for Level 5. You can read more about paint sheen in our article on semi-gloss paint.
How to choose the right level
Ask yourself:
- Will the wall or ceiling be lit from a low angle by windows, skylights or downlights?
- Will you use gloss, semi-gloss or a dark colour?
- Is it a feature area where you'll notice imperfections, like a main living wall or a long hallway?
If you answered yes to any of these, talk to your plasterer about Level 5 for those areas. You don't have to do the whole house. Many people choose Level 4 for bedrooms and Level 5 for living areas, hallways and feature walls.
Why it needs to be decided early
The level of finish affects how the board is installed, how many coats are applied and how long the job takes. Level 5 costs more because of the extra skim coat, sanding and drying time. It's much easier and cheaper to plan it from the start than to fix walls after they've been painted.
When comparing quotes, check which level of finish each plasterer is quoting. Two quotes that look very different on price may be for different levels of finish.
Get a finish you'll love in any light
At Sydney Wide Plastering, we'll look at your windows, lighting plan and paint choices and recommend the right level of finish for each room. For a premium, ultra-smooth look, you can also read about white set plaster.
Planning a new build or renovation? Contact us and we'll help you get the finish right the first time.