Matching a missing moulding profile
Applies to: Assumes a run of original interior moulding partly lost, with at least one intact length remaining somewhere in the building.
Last worked on 2014-12-16
Matching a profile is a measuring problem before it is a machining problem. Four measurements and one accurate section will get a run made.
Find an intact length
Look in the least-altered parts of the building: the top floor, inside cupboards, behind later partitions, and on the back of doors. A single clean length of the original is worth more than any amount of description.
If nothing survives in the room, a length from elsewhere in the same building is usually the same run, because a house of any given date was trimmed out from a small number of profiles.
Taking the section
The reliable method is a physical section rather than a drawing. A profile gauge pressed onto a clean length records the shape directly; the gauge is then traced onto card and cut out to give a template that can be offered back up to the original to check.
Take the section on a length that has not been repeatedly painted, or strip a short area first, because accumulated paint rounds every arris and softens every quirk. A profile taken over paint comes back visibly wrong.
The four measurements
Overall width and overall projection set the blank size. The rebate or ground depth sets how the moulding sits against the surface behind it. The largest single radius in the profile determines the cutter and is the measurement most often lost when a template is traced carelessly.
Record the species and the direction of the grain as well, because a match in shape and a mismatch in timber is still visible under a clear finish.
Accepting a near match
Where an exact match is not available, a near match is far more convincing in some positions than others. A run that meets the original at an internal corner reads as a change of material; a run that meets it in the middle of a straight wall reads as a mistake.
Planning where the joint between old and new falls is the part of the job that decides whether the repair is noticed.
What to record before ordering
- Overall width
- The full face dimension of the moulding, measured on a clean unpainted length.
- Overall projection
- How far the moulding stands off the surface it is fixed to.
- Ground or rebate
- Any recess on the back that lets the moulding sit over the surface behind it.
- Largest radius
- The biggest single curve in the profile, which usually determines the cutter.
- Species and grain
- Recorded from a fresh cut end rather than from the finished face.
The commonest reason a matched run does not match is a template traced over paint. Strip a hand's width of the original first and the rest of the job becomes straightforward.