# Installing a Coffered Plywood Ceiling

• 20-30 hours
• Intermediate
• 1,200-2,000
What You'll Need
Tape measure
Ruler/straight edge
Pencil
Graph paper
Nail gun
Miter saw
Table saw
5-inch wide studs
1x4 timber
Moldings for interior corner trim
Wood glue
Caulk tube
Protective goggles
Gloves

An attractive feature for traditional homes is a coffered plywood ceiling. This type of ceiling is most often found in older, stately houses. Its name derives from the recessed panels bordered by beams.

These beams are not usually solid. They are constructed using a box design and can often disguise ugly structural beams used for the initial construction. They not only give a room a more formal appearance, but they also provide superior acoustic properties.

Installing a coffered ceiling is a project that should be taken on by those with advanced knowledge of carpentry. The coffered beams may be constructed over an existing plywood ceiling, making it more attractive.

## Calculate the Beam Positions

The position of the coffers should be calculated by measuring the ceiling. Pay particular attention to the position of any light fittings. Mark any walls that touch the ceiling with a thick line on the graph paper. The coffers may be rectangular, square, or any other pleasing shape. Note any odd protrusions that may affect the measurements.

Coffers look better in a symmetrical pattern. A box-shaped room should be divided into equal sections. For example, a 15-foot room may be divided up into three 5-foot sections.

## Draw the Ceiling Plan

Lightly draw a dashed line on the graph paper showing approximate dimensions of the ceiling. If these lines cross an obstruction, recalculate the position of the beams. The coffered beams are constructed by nailing a 5-inch wide stud to the ceiling joists and attaching 1-inch thick timber to the sides of it.

## Calculate the Coffer

To calculate the dimensions of the coffers, subtract two times the thickness of the side timber and add the thickness of the beam for each coffer in the room. Using the original ceiling dimension of 15-feet, subtract the widths of the number of beams and what remains gets divided by how many recessed areas were drawn on the graph paper.

For example, if the room measures 15-feet long. The timber used for the side of the coffers is 1-inch thick. The actual beam support is 5-inches wide. On the drawing, the 15-feet is divided into three panels supported by two beams. The original room length is 15-feet minus the two beams at 7-inches total width each, which leaves a distance of 13-feet and 10-inches. The 13-feet and 10-inches divided by three equals 4-feet 2/3-inch, which is the length of each panel. This process may be repeated to obtain the coffer width.

## Transfer the Dimensions to Paper

Transfer the coffer dimensions to scale on the graph paper. The graph should show the 1-inch boards on the wall as a thin line. The panel is fitted to the outside edge of the wallboards. The wallboard will be positioned across the ceiling.
Record the panel dimensions on the graph for easy recall. Remember that each beam is the width of the stud plus a 1-inch thick length of timber on each side of it. The 5-inch wide studs will be installed first.

## Mark the Ceiling

Standing on the ladder, transfer the measurements from the graph to the ceiling using the pencil and a tape measure. Draw the straight lines with a long piece of wood as the straight edge.

## Attach the Studs

Cut the 7-inch wide studs to length and attach them to the ceiling between the marks you placed in Step-5. Have someone hold the studs against the ceiling, first in one direction, then the other. Form a “U” section of the 1-inch thick boards the entire length of the coffer, then lift it up to cover a stud and nail it onto the sides of the stud to form a hollow beam.

## Attach the Cross Sections

Form shorter “U” sections to fit at right angles between the two main coffers on the ceiling and attach them in the same way as the main coffers.

## Attach the Wall Boards

Cut short sections of 1-inch thick boards and attach them to the walls around the room in between the coffers.

## Finishing

Measure and cut quarter-round trim and attach them between the coffers and the ceiling. Caulk all gaps and nail holes. Apply primer and paint for a neat finish.