How to measure for an overdoor pediment

To measure for an overdoor pediment, measure the full width of your door architrave from outside edge to outside edge, then the height from the top of the architrave to the ceiling or cornice. Choose a pediment that is at least as wide as the architrave, usually a little wider, and that leaves a clear gap below the ceiling or cornice.

Those two numbers, width and clearance, decide almost everything. The rest is proportion: how deep the overhang should be, how tall the pediment can sit and how it relates to the doors and windows around it. Ten minutes with a tape measure saves ordering a piece that looks pinched or crowded.

What you need

• Steel tape measure. Metric is easiest. Write everything down in millimetres.
• Pencil and paper. A quick sketch of the door, architrave and ceiling with numbers on it.
• Spirit level. To check whether the top of the architrave is level. In older houses it often is not.
• Masking tape or card. For marking out the pediment's size on the wall before you commit.

Measure the architrave width

The architrave is the moulded trim around the door opening. Measure across the top of it, from the outer edge on the left to the outer edge on the right. Do not measure the door itself or the opening: the pediment sits on or above the architrave, so that is the width that matters.

For reference, the most common internal door in England and Wales is 762 mm wide and 1981 mm high, the old 2 ft 6 in by 6 ft 6 in size. Add the architrave on each side and the overall width is usually a good deal more than the door. Period houses vary, so measure every door you plan to dress. Doors in the same hall are often different.

Also note the depth of the architrave, how far it stands off the wall. A pediment with a shelf or cornice usually looks best when it projects a little further than the architrave below.

Decide on the overhang

A pediment narrower than the architrave looks like a mistake. One exactly flush can look flat. Most classical overdoors run slightly past the architrave on each side, so the top reads as a cap. There is no single rule, but a modest overhang, enough to see but not enough to dominate, is the usual aim.

• Narrow hallways. Keep the overhang small so the piece does not crowd a side wall, light switch or the next door.
• Wide rooms and tall doors. A broader pediment holds its own and stops the door looking lost.
• Pairs of doors. Use the same piece on both and line the tops up, even if the architraves differ slightly.

Check what is beside the door. A switch plate, radiator or corner close to the architrave limits how far the pediment can extend.

Measure the architrave, not the door. That is the width the pediment has to answer to.

Check the ceiling clearance

Measure from the top of the architrave to the ceiling. If there is a cornice or coving, measure to its lowest edge instead. The pediment needs to fit in that space with a visible gap above it. If it touches or nearly touches the cornice, it looks squeezed and the two mouldings fight.

Modern houses with lower ceilings may have only a small space above the door frame. That suits a shallow pediment or a simple cornice-style topper. Victorian and Georgian rooms with high ceilings can take a taller pediment, or a triangular or swan-neck form. Our article on Palladio and the pediment explains where those shapes come from.

Test the proportion before you order

Cut a piece of card to the pediment's width and height, or mark the outline with masking tape. Fix it above the door and step back to the far side of the room. Look at it from where you normally see the door. Ask three questions: is it wider than the architrave, is there clear space above it and does it feel in scale with the door's height?

Also check the wall above the door. You will need sound plaster or masonry to fix into, and you should know whether any cables or pipes run there. If in doubt, use a detector before drilling.

Ordering and fitting

Once you have your numbers, compare them with the dimensions on each listing in our overdoors and door toppers collection. Each piece is hand-cast to order in Shrewsbury and arrives as natural plaster, ready to paint. Before you fix it, read our fitting instructions for the method we recommend. For ideas on combining an overdoor with other details, see styling a hallway with architectural details.