Arch braces Curved timbers ostensibly rising from the walls to support the cross tie beams of a roof, but largely employed for their visual effect creating arches.
Arris The sharp angle where two worked faces of the same timber meet.
Birdsmouth A carpenter’s term where a right-angled notch is cut on the bottom of a sloping timber to allow it to rest on a horizontal timber.

A timbers in a roof truss, parallel to and above the tie beam, tying together the principal rafters of the roof.

Cusping Within a timber framed panel, decorative round carvings meeting at points
Hammer beam/
False hammer beam
A device found in the larger medieval roofs, designed to allow shorter major timbers to span the space. This was a sign of high gentry status and was simulated by the ‘false hammer beam roof’which is without the vertical hammer post.
Louvre A timber ventilator on the ridge of a roof, usually to let out smoke. Sometimes spelt louver.
Plate A horizontal timber placed on top or within a wall to carry the roof structure.
Post In medieval timber construction, a vertical timber. In a roof, a king post supports the ridge beam; a crown post rises centrally from the tie beam and supports the collar; a queen-post is similar, but are equally spaced away from the centre, and are used instead of a crown post.
Purlin Horizontal timbers spanning between trusses in a roof, carrying the common rafters

A means of joining timbers end to end to make a longer piece of the same cross section.

Bridled scarf is where the upper face of one timber is formed with a tenon, entering in a mortice on the top face of its joining timber and pegged through from the side. There are many variations of scarfed joints.

Soffit The underside of a feature.
Tie beam The major horizontal timbers spanning the space at the top of the walls, usually defining structural ‘bays’.
Waney The edge of any timber where the removed sapwood has prevented the timber from being properly squared up.
Wind braces Straight or curved flat timbers in the angles between the principal rafters of a roof and the purlins, to provide rigidity, especially under pressure from the wind.