Plastering And Cornice Work

September 26, 2022

Plasterers And Cornices

What are cornices?

A cornice - also known as ceiling moulding, cove moulding, or scotia moulding - is the angled plaster between the ceiling and the wall.
You may have seen ornate cornices in Victorian or historic homes, which included elaborate ceiling roses.
These were considered fashionable, and cornices are associated with other eras, including the Edwardian, Georgian, and Art Deco eras of the 1920s and 1930s. Today, homeowners are still attracted to these features, which is why cornice replicas are made to match these historical designs.
Hire a plasterer skilled in ornate plastering if you want to outsource any plastering work.

What is the purpose of a cornice?

Cornices primarily serve a decorative function, but they can also help hide messy joints at the ceiling-wall junction or cracks caused by aging, settling and movement of a building. 

What are cornices made of?

Plaster- Cement, lime or gypsum are used to make plaster cornices. These materials are expensive but can be painted with oil or water-based paints. Plaster cornices must be applied with care by a skilled plasterer

Plaster or gypsum covered with paper is made of lime or gypsum, which is pressed between two layers of paper.


cornice work

What is the difference between the cornice and crown moulding?

After a Google search, you may feel quite confused. Cornices are decorative crown moulding, but crown moulding is cornice - none of this makes sense! So let's remove this confusion once and for all. Both are decorative mouldings used to cover the transition between the wall and the roof, balcony or ceiling.

Crown mouldings make the surface crown of something! On buildings, the decorative edges of the outer crown mouldings taper upward and extend beyond the top of the wall.

Cornices are essentially a kind of crown moulding. They sit at the top of the wall and project outward, with the uppermost edges protruding at the roofline. 

What is the difference between a ceiling coving and a cornice?

Some plasterers distinguish between cornice and coving.

A cornice is a generic term for moulding designed to conceal the transition between the wall and ceiling. Coving often refers to a type of cornice that has a uniform profile. Like hoover is the colloquial term for a vacuum cleaner, coving is now used to refer to any form of a cornice. In Australia, the word coving refers to mouldings/ cornices and a plasterer is who you would employbuilding to install them.


Equipment and materials for cutting and installing cornices

Get ready with these tools and materials before you start cutting and attaching cornices:

  • A fine-toothed handsaw 
  •  A mitre box or block
  •  Adhesive for cornices/projections or silicone adhesive
  • Spirit level
  • Pencil and chalk line 
  • Hammer and board pins 
  • Sponge and water 
  • Sandpaper to clean up end joints
  • Stanley knife 
  • Mechanical fasteners

How to cut a cornice?

Cornices are usually cut with a fine or medium tooth saw, but you should first measure your room to get all the dimensions.

If you are cutting a cornice to join the corners of a room, a mitre box will ensure that an accurate angle can be cut. This way, the two cornice sections can be neatly joined together, provided your room is perfectly square. But, of course, finding the right angle is easier said than done, so it's no surprise that people can be seen struggling to get it right on DIY forums. 

Cut your section by securing it in the mitre box and cutting it without any movement. This is the only method to ensure a precise cut.

At what angle do you cut the cornice corners?

Forty-five degrees is the correct angle. It looks like you laid the cornices flat in the mitre box to cut them. It would help if you cut the angle so that the cornice is upright, as it would be with the cabinets.

How should we measure the size of the cornice?

The cornice or cove's size is measured in a straight line across the face or visible side of the profile. 

There are three other important measurements:

  • The projection: indicates how far the cornice extends from the wall into the ceiling.
  • The slope or height is how far the cornice falls down the wall.
  • The length indicates how long the profile is and how far it covers the ceiling-wall junction.

Why is my cornice ceiling sagging?

The age of the ceiling and the building itself can often be the cause of cracks or sagging. As the building ages, the fasteners and adhesives that hold it together also change. Cracks can occur when cornices, ceilings and walls settle in their places.

How do you repair a sagging cornice ceiling?

Step 1

Use a paint scraper to remove loose paint or plaster along the crack.

Step 2

Mix the cement of cornice in a bucket to form a paste. Use a scraper to fill the gap between the cornice and ceiling with cornice paste/cement.

Step 3

Use the drill to screw up gypsum board screws through the cornice into the ceiling so that the cement comes out of the crack. Remove excess cement with a scraper and use it to fill the screw heads.

Step 4

Allow the cornice cement to set for a few minutes, then wipe along the crack with a damp, lint-free rag or sponge to create a smooth surface.

Step 5

When the cement is completely dry, lightly sand it if needed and then apply a primer or sealer.
Allow the cement to dry, and then apply two topcoats of acrylic paint in the same colour as the ceiling.
Read more about Renovations and Restorations when plastering

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