Moulding proportions by ceiling height

At a glance

Millimetres from finished floor, rounded to 5 mm. Our arithmetic on rules in circulation: skirting 2.5 to 7%; cornice projection 2.5 to 5%; dado rail top a fifth to a third; picture rail about 300 below the ceiling. Starting points, not standards. Architrave and cornice drop: no ratio rule found.

How to use the table

Pick the ceiling height in the first column and read across for a range in each band. The ranges are wide on purpose: they are what the rules give, and the rules disagree. A designer chooses a point inside each range, draws it, and tests it on a mock-up in the room. The architrave is missing because we found no ratio rule for it: it is set from the profile and from how it meets the skirting, as our skirting and architrave sizes sheet shows. The cornice drop and the frieze are missing for the same reason.

Two warnings the table cannot show. The dado fractions give very tall rails in tall rooms (a third of 4.2 m is 1,400 mm), while the one published range we have, 26 to 32 in. (660 to 813 mm), is meant for any ceiling. And the 300 mm picture rail drop is a period convention from a source that cites nothing; the same wiki says Victorian rails sat around the height of tall door architraves. Treat both as prompts to look at the room.

Where each rule comes from

This is the weakest part of the topic, so the sheet shows the provenance rather than hiding it. None of the sources is a standard or a conservation record.

The skirting, dado and picture-rail rules are set out with their sources on the skirting and architrave and dado, chair, picture and plate rails sheets. For cornice, see the sheet on cornice, crown moulding and coving. The profiles themselves are on moulding profiles.

A worked 3.0 m wall

The table gives, for 3.0 m: skirting 75 to 210, cornice projection 75 to 150, dado rail top 600 to 1,000, picture rail top 2,700. Choose a point in each: skirting 150, dado rail top 800, a cornice that drops 120. Then every band is fixed and they add up to the ceiling height. This is an example of the method, not a recommended room.

Seeing the bands as heights exposes clashes the ranges hide: a frieze of 180 mm is narrow beside a 1,900 mm field, and a dado of 650 mm is a little over a fifth of the wall. If the room has a door, tie the dado rail to the window stool or the door architrave so the lines meet: see wall panelling set-out and architrave profiles and door casings.

What overrides proportion

• The building. In an older house, surviving mouldings, paint lines and marks are better evidence than a ratio: match them.
• Fixed datums. A window stool, a door head, a stair handrail or a floor build-up decides a height before a fraction can.
• The profile. A cornice's projection and drop depend on its profile, which is a design decision: see moulding materials compared for what each material can make.
• Fire, in England. Approved Document B Volume 2 leaves “architraves, cover moulds, picture rails, skirtings and similar narrow members” out of what counts as a wall lining (paragraph 6.3(c)), and architraves, cover moulds, picture rails, exposed beams and similar narrow members out of a ceiling (paragraph 6.6(c)); the 2019 edition with amendments to 2026, as read in November 2026. Cornices and dado rails are not named, so whether they count is for the fire engineer or building control. Wales, Scotland and Northern Ireland were not read.

Sizes in this schedule are set by the designer and shown on the drawings: skirting [150] mm high, dado rail top [800] mm, picture rail top [2,700] mm, cornice projection [100] mm and drop [120] mm, all from finished floor level and the ceiling as built. No proportion rule (a fraction of the ceiling height) is to be applied by the workshop in place of a drawn size.

Before production, a mock-up of the skirting, dado rail and cornice at the sizes above is to be fixed on [one wall] of [room] and approved by [designer]. Sizes may be adjusted by up to [ ] mm at that stage; the adjusted sizes become the schedule.

Dado rail top is tied to [the window stool / the door head] at [ ] mm. Picture rail and cornice are measured from the finished ceiling [at the highest point of the room]. The contractor is to confirm the ceiling height as built before the schedule is issued.

Standards and sources

• Approved Document B Volume 2 (England), 2019 edition with amendments to 2026: paragraphs 6.3 and 6.6. Read 7 Nov 2026.
• No standard fixes any moulding proportion: the rules in the table are conventions; none is taken from a British Standard.

Questions we are asked

What size should skirting be for a given ceiling height?

No standard sets it. The rules that circulate give 2.5 to 7 per cent of the ceiling height, which is 60 to 170 mm at 2.4 m and 75 to 210 mm at 3.0 m. Choose a size inside the range for the room and its profile, draw it, and mock it up.

How big should a cornice be for a 3 m ceiling?

No standard sets it. Two manufacturers' guides give a projection of 2.5 to 5 per cent of the ceiling height as a starting point, which is 75 to 150 mm at 3.0 m. We found no ratio for the drop. Use surviving cornice in an old house as the reference.

How high should a dado rail be?

No standard or regulation sets it. The sources we read give 26 to 32 inches (660 to 813 mm), or a fifth to a third of the wall height, or the height of the window stool. They disagree in tall rooms.

How far below the ceiling should a picture rail be?

One period source says Victorian rails dropped about a foot (300 mm), and Georgian rails were hidden in the cornice. None cites a primary source. Match the room, or draw a height.

Do dado rails and cornices need a fire rating in England?

Approved Document B Volume 2 names picture rails, architraves, cover moulds and skirtings among narrow members left out of the wall lining classification, and does not name dado rails or cornices. Whether they count is for the fire engineer or building control.