Coffered, tray or waffle ceiling

All three change the ceiling from a flat plane into something with depth, and all three get called by each other's names. They are different in how they are built and in how much ceiling they need.

Coffered

A grid of beams across the ceiling, dividing it into sunken bays. The beams can be simple boxes or carry mouldings on every face. The depth of the beams is what makes the shadow lines, and it is also what brings the ceiling down visually, so a coffered ceiling reads best with height to spare.

Waffle

A coffered ceiling with a tight, even grid of square bays. The name describes the look. It is built the same way, with more beams and more intersections, and every intersection has to line up.

Tray

A ceiling with a raised centre, so the perimeter steps down around the room. There is no grid. The trim around the step is what makes a tray ceiling read as deliberate. It suits rooms where a full coffered grid would feel heavy, and works in lower rooms than a coffered ceiling does.

Which suits which room

• Coffered: living rooms, libraries and dining rooms with nine foot ceilings or more
• Waffle: large rooms where a bigger grid would leave oversized bays
• Tray: bedrooms and dining rooms, and rooms where the ceiling height is modest

Building one into an existing house

Beams for a coffered or waffle ceiling are built onto the ceiling that is already there. Very few ceilings are perfectly level, so the grid is set out against a level line rather than against the ceiling itself, and the beams are scribed to meet it. Light fixtures, sprinklers, speakers and vents are planned into the grid before anything goes up, so they land in the centre of a bay.