The following is a working glossary, sometimes specific to our usage here at PTF. The TFGuild’s glossary is also a good reference. Please contact Jessica MilNeil if there is any terminology you would like to see added.
Bed Timber: Large horizontal framing member that crosses two or more tie beams and supports the belfry or clock tower frame within a steeple.
Bent: Refers to a bread slice of framing members parallel to the gable, and containing posts, a gable sill, floor girts, tie beam and rafters. Bents are typically numbered, starting at the reference end of the building, if there is one.
Cog: This is a square cut-out from the top edge of a rafter horizontal framing member. The L-shaped end of joist or purlin usually drops into it. Sometimes purlins also contain a cog, and they join to a rafter like two hands cupping one another.
Collar tie: A small horizontal roof framing member. It connects an opposite pair of rafters, in the upper half of their height. In older frames, collar ties are tenoned into mortises in the rafters, creating an especially strong roof frame.
Cornice: The collection of trim located at the top of an exterior wall, where it meets the roof. The cornice is composed of crown, fascia, soffit, bed molding and sometimes a frieze.
Eave: The side of the house parallel with the slope of the roof, and parallel with the plate.
English Tying Joint: A double mortise and tenon connection used to join the top of a post, usually a gunstock, to both the tie beam and the plate. The top of the post is cut into two tenons which are oriented perpendicular to one another and run parallel to the length of the mortises they enter. The tenon which enters the tie beam is called a teasel tenon. The plate and tie are not only mortised to accept the post, but are connected to one another by a lapped half dovetail joint.
Frieze: A wide horizontal trim board hung at the top of a wall directly beneath the soffit. Characteristic of a drop tie frame and the Greek Revival period.
Gable: The face of the house parallel with the triangle created by the two slopes of the roof, or parallel with the tie beam in the case of a hip-roofed house.
Girt: A horizontal framing member within the floor or wall plane. It usually goes from post to post, or sill to sill. Frequently cogs are cut into it, and floor joists rest on it. A chimney girt runs adjacent to the chimney mass. It is frequently larger, and runs from eave to eave, when in the first floor framing, chimney girts are also called carrying timbers.
Joist: A smaller floor or ceiling framing member. They rest on sills, girts, tie beams, and sometimes plates. They provide a nailing surface for flooring or ceiling plaster and lath and sometimes both.
Joist pocket: A square void cut out of the top edge of a floor girt, sill or tie beam, usually occurring in a series that indicates joist layout. The L-shaped end of a joist drops into this.
Mortise: Square hole in a framing member, a tenon fits into it to create a mortise and tenon joint. This joint is typically pinned together, and is what allows timber frame structures to be assembled without nails. This is the primary joint that distinguishes a timber frame from later platform, balloon, or post and beam structures.
Plate: Horizontal framing member, sits atop the posts, parallel with the eave.
Post: Main vertical framing members, in corners and within walls. Connect the sill to the plate. A gunstock post is one that tapers, narrower at the bottom and wider at the top. It is wider at the top to accommodate two tenons, one that goes into the tie beam, and one that goes into the plate. A gunstock post is typically found in older frames.
Purlins: Horizontal roof framing members that run from rafter to rafter. They provide nailing surface for roof sheathing.
Rafters: Diagonal roof framing members, create the roof pitch, contain cogs in which the roof purlins sit.
Sill: Horizontal framing member that sits on foundation. Posts stand upon it, first floor girts and carrying timbers fit into cogs or mortises along its length.
Sleeper: Horizontal framing member that runs across other framing members and supports framing above it. They are usually large, upwards of 10”x10” and are often used in steeples, crossing tie beams or girts and supporting the frame of a tower box or belfry telescoped deep inside the building.
Soffit: The horizontal section of exterior trim that projects from top of the wall. Combined with the fascia, crown, bed molding, and sometimes the frieze, it creates the cornice.
Summer Beam: Horizontal first floor framing member. A summer beam is like a floor girt, but it has larger dimensions and it runs from gable sill to gable sill. Sometimes called a carrying timber.
Tenon: The “male” part of a mortise and tenon joint. It occurs on the end of a framing member (such as a post or girt), and its dimensions are reduced from the size of the rest of piece in order to fit into the mortise.
Tie Beam: Horizontal framing member, runs parallel to gable. Keeps the eave walls from falling out by resisting the outward thrust of the rafters.
Water Table: Horizontal trim piece at the bottom of an exterior wall plane. Provides a visual termination of the wall cladding, and creates a drip line away from the foundation below it.
This glossary was written by Jessica MilNeil and is the property of Preservation Timber Framing. We encourage its sharing, but please credit its use.