Architrave and casing

Frequently asked questions

How much architrave does one door actually take?

Usually more than the obvious sum, and the mitres are why. A single side of a standard doorway takes two vertical legs and one head, and if each leg is cut from the opening height and the head from the opening width you have measured the SHORT edge of a mitred piece — the long edge of each piece is longer by the width of the moulding at each mitred end. Then a door that is trimmed on both faces doubles everything, which people forget on internal doors. Stock lengths make it worse: legs commonly come from a length that leaves an offcut too short for another leg, so the practical order is set by how the stock divides rather than by the total run. Ordering the bare run plus a nominal percentage tends to fall short on a job with many doors.

What is the difference between architrave and the lining?

Which surface it covers, and they are two separate orders. The lining — jamb in Australian and American usage — is the board forming the INSIDE of the opening, the surface you see when you stand in the doorway and look at the edge of the wall; it is as wide as the wall is thick, and it is what the door stop and the hinges are fixed to. The architrave is the moulding on the FACE of the wall, covering the joint where the lining meets the plaster. A door set quoted as including casing in North America may include both, whereas a British quote for architrave rarely includes the lining. That is one of the commoner mismatches when a package is priced from a specification written in another market.

Why do some mitres open up and others do not?

Because the moulding is still moving after it is fixed, and the mitre is the joint least able to tolerate it. Timber shrinks across its width far more than along its length, so a mitred corner — where the grain of one piece meets the grain of another at forty-five degrees — opens as the two pieces shrink in different directions. That is why a mitre cut in timber delivered wet, or fixed in a building still drying out, is the one that gapes months later, and why MDF mouldings, which move much less across their width, tend to hold a mitre better while being far less tolerant of damp. The other cause is mechanical: a mitre held only by the paint pulls apart, whereas one glued and pinned through the joint stays closed even when the pieces move.