How to Make Curved Ceiling Moulding Out of Plaster

Written by f.r.r. mallory
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How to Make Curved Ceiling Moulding Out of Plaster
Plaster ceiling moulding with painted and gold leaf trim. (antique ceiling image by John Sfondilias from

Curved ceiling mouldings made of plaster are not as common in homes being built today. One reason is that the use of plaster has changed. Most modern homes use drywall with a thin application of texture, if the homeowner wants texture. Plaster walls were built over lath and mesh and the plaster was applied like a coat of mud. This thickness allowed the plaster to form a wall surface and because plaster dries quickly and holds shapes, many types of plaster mouldings were developed and used to decorate walls and ceilings. Medallion shapes centred over a drop light fixture were often standard requests for a plasterer working on a formal style home. The technique for creating a medallion or circle shape in plaster on the ceiling isn't actually that difficult.

Skill level:

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Things you need

  • Ladder
  • Tape measure
  • String
  • Pencil
  • Tin snips
  • Files
  • 1 x 2-inch board
  • U bracket
  • Screws
  • Screwdriver
  • Plastic sheeting
  • Polyvinyl acetate (Plaster weld)
  • Disposable paint brush
  • Galvanised bugle head screws
  • Rubber gloves
  • Safety goggles
  • Plaster
  • Lime putty
  • Powdered retarder
  • Putty knife
  • Sandpaper

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  1. 1

    Turn off the electricity to the room at the breaker box and remove the chandelier light fixture. Tuck the wires up out of the way after you screw the caps on them. You should have a threaded post-type fitting in the centre of the electrical box. Tie a loop in the end of some string. Place the loop over the threaded fitting. If your box doesn't have this fitting, wedge scrap 2 x 4-inch wood inside the electrical box with a protruding screw. Pull the string taut. Attach a pencil at the distance you think is a good size for a plaster moulding circle. Draw the circle.

  2. 2

    Step down and look up. If your circle needs to be larger or smaller then redraw it until the size looks proportional to the room. Select a piece of flat moulding that has the profile you want to create. Trace this profile onto a wide metal putty knife. Cut the profile out with tin snips and file the profile until it is smooth. The contoured putty knife is called a screed.

  3. 3

    Attach the screed to a 1 x 2-inch board by using a drill, bolts and nuts. Hold the screed and wood against the ceiling so that the outside contour of the screed matches your drawn circle. Mark the other end of the wood 1/4-inch from where it touches the threaded post. Cut the wood. Attach a U-shaped bracket on the end of the board so that when the edge of the screed is flat while touching the ceiling the bracket will surround the threaded post. Attach the bracket to the wood.

  4. 4

    Cover the floor with plastic sheeting. Scratch the ceiling inside the circle so the plaster will adhere better. Paint the ceiling inside the circle with polyvinyl acetate (Plasterweld). Drive galvanised bugle head screws into the drywall in the area where you will screed. Allow just the heads to stick out. Put on rubber gloves and safety goggles.

  5. 5

    Trowel equal parts plaster and lime putty to the ceiling. Add a powdered retarder (in the ratio recommended by the manufacturer) to slow the drying process. Attach your armature and screed and drag the screed evenly around the circle to form the plaster shape you desire. Clean off any excess plaster. Sand after the plaster has hardened.

Tips and warnings

  • You can modify your armature to catch some of the dropping plaster from the screed using plastic or plywood. You can attach decorative embellishments with plaster as the bond. Pre-plan your design on the floor so your spacing is worked out in advance.

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