Cornices
Cornices near you
A cornice is the moulding that closes the junction between a wall and a ceiling, and in Australia it is almost universal. The reason is structural rather than decorative. The wall frame and the ceiling frame are separate structures that move independently, so the line where they meet is the one place in a room guaranteed to open up. A cornice bridges that line with a wide, forgiving profile that hides a few millimetres of movement without anyone noticing.
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That is also why the alternative, a square set junction with no cornice at all, is a considered decision rather than a saving. Square set gives the crisp shadowless line that modern Australian architecture likes, but it removes the tolerance, so the junction has to be detailed and set properly or it cracks. In a house on reactive clay soil, which describes a great deal of suburban Australia, that is a real risk and not a theoretical one.
Beyond the choice of whether to have one, the decisions are about profile and scale. Australian housing eras have recognisable cornices: the deep ornate runs of Victorian and Federation houses, the stepped and geometric profiles of the interwar period, the simple cove of post-war and project housing, and the shadow line and square set details of contemporary work. Getting the scale right for the ceiling height matters more than the ornament, because a profile that suits a high Federation ceiling looks oppressive in a standard modern room.
Cornice profiles and what suits which Australian house
- Plain cove is the default in post-war and project housing, an economical concave run that suits standard ceiling heights and takes paint well.
- Stepped and geometric profiles belong to interwar and mid-century houses and read as period-correct in a way a plain cove does not.
- Ornate and decorated runs suit Victorian, Federation and Edwardian rooms with high ceilings, where a deep profile is in proportion.
- Shadow line detailing replaces the cornice with a deliberate recessed gap, giving a clean line while still allowing some movement.
- Square set removes the junction entirely for a sharp wall-to-ceiling line, which is the most demanding option to execute and the most prone to cracking.
- Coffered and bulkhead details combine cornice runs with dropped ceiling sections, and are often used to conceal ducting or lighting.
- Lighting cornices and cove details with a concealed strip create indirect light, and need the electrical work planned before the plasterwork.
How cornice is installed and why the setting out matters
- Ceiling and wall linings are completed and the junction is cleaned out, because cornice fixed over loose or proud material will not sit flat.
- The run is set out from the most visible corner, so any necessary adjustment falls where nobody looks rather than across a main sightline.
- A line is struck on both the wall and the ceiling to keep the cornice height consistent, which is what stops a run drifting along a long wall.
- Lengths are cut with mitres at external corners and either mitred or scribed internally depending on the profile and the plasterer's method.
- Adhesive is applied to both contact faces and the length is bedded firmly, with excess cleaned out of the joint before it goes off.
- Joints and mitres are filled and worked while the material is still green, because a joint finished after the adhesive has hardened is much harder to hide.
- The finished run is sanded lightly and sealed before painting, and the junction is not caulked unless the profile and the situation call for it.
- Decorative runs may be built up from several components, and each one has to be set out so the ornament lines up around the room.
Cracking at the cornice: what it means
Cracking along a cornice is common in Australian houses and most of it is benign. A hairline that appears along one edge of the run, usually the ceiling side, and opens and closes with the seasons is ordinary differential movement between a wall frame and a ceiling frame. It is cosmetic, it will come back if it is simply filled with a rigid compound, and it is one of the reasons cornice exists.
What is not benign is a crack that steps, widens along its length, appears at the same time as cracking in the brickwork or the floor, or comes with doors and windows binding. That combination points at foundation or structural movement rather than surface movement, and much of suburban Australia sits on reactive clay that swells and shrinks with moisture, which makes it a genuinely common cause. Drainage, a leaking service, a large tree or a change in watering can all drive it.
In those cases the cornice is a symptom, and repairing it before the cause is addressed simply buys a season. The right order is to have the movement assessed, deal with whatever is driving it, allow time to see whether it stabilises, and then repair the finishes. Our plaster repair and ceiling repair guides cover that repair work, including the materials used in pre-1990 cornices and the tools that must not be used on them.
Cornice, shadow line or square set
Cornice is the tolerant option. It covers a junction that will move, it hides small imperfections in both the wall and the ceiling lines, it is quick to install and it is easy to repair. In an older house, or any house where movement is expected, it is the low-risk choice, and the only real argument against it is aesthetic.
A shadow line sits in between. The junction is detailed with a deliberate recess, so the eye reads a clean modern line while the gap still allows some movement without cracking a visible surface. It costs more than a cove because it requires a proprietary bead and careful setting, and it is less forgiving of an out-of-square room, but it is far more robust than a full square set.
Square set is the demanding option. With no cornice and no recess, the wall and ceiling meet in a single set line, so everything depends on the framing being accurate, the junction being reinforced properly and the building not moving. In a well-built house on stable ground it looks superb. On reactive clay, in a house with a long unsupported ceiling span, or in a room where the framing is not square, it is the detail most likely to need repeated repair.
What cornices are made from
- Plaster cornice cast in gypsum is the Australian standard, available in long lengths in every common profile and fixed with a cement-based adhesive.
- Fibrous plaster with a reinforcing fibre is used for decorative and custom runs, and is what most heritage reproduction work is made from.
- Timber cornice appears in some period and contemporary work, fixed mechanically like trim rather than bedded in adhesive, and it moves seasonally.
- Polyurethane and expanded polymer cornices are light, water-tolerant and easy to fit, which makes them a practical option in wet areas and for retrofits.
- Proprietary shadow line beads are metal or plastic sections set into the junction rather than a moulding applied over it.
- Custom-run profiles can be cast from an existing section, which is how a missing length in a Federation room is matched properly.
- In pre-1990 houses, do not assume what an existing cornice or its bedding is made of: have it assessed before cutting, drilling or sanding it.
What changes the price of a cornice job
- The profile, since a plain cove is a fraction of the labour of a decorative run built from several components.
- The total length of run, which is driven by the number of rooms rather than their floor area.
- Ceiling height, because anything above a comfortable reach needs platforms and slows every operation.
- The number of internal and external corners, since corners are where the time goes and a room with a bay or a nib wall has many.
- Whether existing cornice has to be removed first, and what condition the wall and ceiling junction is left in.
- Access and protection in an occupied house, because plaster dust and adhesive splatter travel further than people expect.
- Any custom casting required to match an existing profile, which is a manufacturing cost rather than an installation one.
- Making good and painting afterwards, which is a separate trade and should be a separate line in the quote.
Cornices: frequently asked questions
What is the difference between cornice and square set?
Cornice is a moulding that covers the wall-to-ceiling junction; square set finishes that junction as a single sharp line with nothing over it. Cornice is tolerant of movement and of small inaccuracies in the framing. Square set looks cleaner and more modern but removes that tolerance, so it demands accurate framing, proper reinforcement at the junction and a building that does not move much.
Why does the crack above my cornice keep coming back?
Because it is a movement joint being treated as a defect. The wall frame and the ceiling frame move independently, so a hairline along the edge of the run opens and closes seasonally. Filling it with a rigid compound guarantees it reopens. Where the movement is ordinary, a flexible treatment at that edge is the durable answer; where the crack steps or widens, the cause is structural and needs assessing first.
What size cornice suits a standard Australian ceiling?
Scale it to the ceiling height and the era of the house. A modest cove suits standard modern ceilings, while a deep ornate profile needs the height of a Federation or Victorian room to look right and will feel oppressive in a low one. In a period house, match the profile that survives elsewhere in the building rather than choosing from a catalogue, and take an offcut to the supplier.
Can cornice be added to a house that never had it?
Yes, and it is a common retrofit, particularly where a square set junction keeps cracking. The junction is cleaned out, the run is set out to a struck line and bedded in adhesive, and the joints are filled and finished. The main things to check first are whether the existing linings are sound enough to take it and, in a pre-1990 house, what those linings and any existing material at the junction actually are.
Is cornice suitable in a bathroom?
Yes, but choose the material for the conditions. Gypsum plaster in a poorly ventilated bathroom will eventually suffer, so a polyurethane or composite cornice that does not absorb moisture is the more durable option, as is making sure the room is actually ventilated. Persistent mould at a bathroom cornice is a ventilation problem showing up at the coldest surface in the room, not a cornice problem.
Who installs cornice, a plasterer or a carpenter?
A plasterer, for anything bedded in adhesive, which covers plaster, fibrous plaster and most composite profiles. Timber cornice is carpentry, because it is fixed mechanically and mitred like trim. Painting is a third trade again. On a renovation it is worth agreeing who fills the joints and who seals the run before painting, since that handover is where finish problems usually originate.
Sources
Written by the LokalMatch editorial team. Last reviewed 22 September 2026. How we write and check our guides
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What affects the cost of crown moulding
Prices depend on the details of your project. We only publish price ranges when they’re backed by real LokalMatch quote data or reliable sources. Until then, here’s what usually changes the price:
- Size of the area and ceiling height
- Condition of the walls, trim or siding
- Amount of prep and repairs
- Number of colours and coats
- Paint quality
- Access, including stairwells and upper floors
How to compare finish carpenters before you hire
- Ask how the painter will prepare the surfaces, since patching, sanding and priming matter as much as the paint.
- Get a written quote that lists which rooms or surfaces are included, the number of coats and who supplies the paint.
- Ask how they'll protect floors, furniture, landscaping and anything they can't move.
- In older homes, ask how they handle old paint that may contain lead.
- Look at recent work, paying attention to clean lines at ceilings and trim.
Questions to ask finish carpenters before you hire
- What prep work is included, such as patching, sanding, caulking and priming?
- How many coats are included, and what paint will you use?
- Are ceilings, trim, doors and closets part of the price?
- How will you protect my floors, furniture and plants?
- Can you show me proof of liability insurance?
- What happens if I notice touch-ups needed after you finish?
Crown moulding permits and local rules
Some crown moulding work needs a permit or has to meet local bylaws. Rules vary by municipality, so ask your pro whether a permit is needed and who will apply for it — and check with your city or town if you’re unsure.
Permits and licensingGuides about crown moulding
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Carpenters guide
Carpentry in Australia divides into trades that often arrive on site months apart. Frame carpenters set out and erect the floor, wall and roof structure, fit the bracing and tie the frame down.
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Trim & Moulding guide
Skirtings, architraves, window reveals, door stops and sill trims are the joinery that finishes a room, and in an Australian house they do a job people rarely think about: they cover the gap where two materials that…
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Framing guide
Framing is the skeleton: the floor structure, the wall frames, the roof trusses or conventional roof, and the bracing and tie-downs that hold the whole assembly together when the weather arrives.
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