As a new comer to the timber framing craft, I admit it’s taken me some time to become familiar with timber framing terms. Did you know there is a difference between the terms Post & Beam and Timber Frame? I didn’t. I also didn’t know that Truss and Bent are interchangeable terms, but Hand Hewn and Rough Hewn are not. So to help with all the intricacies of a very old craft, I’ve taken it upon myself to compile a cheat sheet of some of the most common timber frame terms and their meanings.
Timber Frame: A structure constructed using heavy timber that is fitted together, or joined, with mortise and tenon joinery. Timber frames are more complicated and have more intricate joinery than post & beam structures.
Post & Beam: Like timber frames, post and beam structures are constructed with heavy timber or logs, but are more simple, using just posts, beams, and rafters.
Timber: A squared off piece of wood that is used structurally.
Bent: A pre-assembled structural framework of beams.
Post: The primary vertical timbers in a timber frame.
Beam: The primary horizontal support timbers in a timber frame.
Rafters: Series of timbers that are used to support roofs.
Brace: A diagonal piece of timber used to support beams.
Joist: Horizontal timbers used to support floors and ceilings.
Purlin: A horizontal roof beam that supports rafters and spans the distance between gable ends.
Chord: The bottom horizontal timber in a truss.
Gable: The triangular upper part of a wall that connects to a pitched roof.
Collar Tie: A horizontal beam between roof rafters that reduces spreading or sagging of the rafters.
Tension Tie: A tension tie is a steel rod that acts as the bottom chord for a truss and allows for large, open, arched truss designs, because the rod carries structural loads.
Post Base: The connection between the bottom of the post and the concrete.
Glulam: Layers of 1 or 1-1/2 inch boards that are glued together to form a beam.
Hand Hewn: A beam that has been hand crafted with an adze and a slick to get a scored, decorative texture.
Rough Hewn: Beams that have been reclaimed from old mill buildings and barns.
Rough Sawn: Timber that has not been sanded or smoothed, but is used as originally cut.
Shake: Shake is the separation of the rings in a piece of wood that occurs as the wood dries. Usually found in Hemlock.
Checking: Checking is a long crack that appears as the sap wood of a timber shrinks around the heart wood over time. Checking is not a structural problem, and usually occurs only on one or two sides of a beam.
Adze: A tool with a long wooden handle with a steel plate at a right angle used to make decorative cuts in heavy timber.
Slick: A tool used to clean the surface of hand hewn beams.
Truss: A structural framework used to support external loads.
King Post: A truss with a center vertical beam with an angled support beam on each side of the vertical beam.
Queen Post: A truss with two vertical beams that each have an outer angled support beam.
Scissor: A truss shaped like a scissor with bottom chords that cross each other.
Hammer Beam: A truss with short beams that extend from and transfer loads to the wall and roof. Because the truss transfers its load to the outer walls and roof, it is able to have an open, arch design. The hammer beam truss design originated in old European cathedrals.
Joinery: Two or more timbers that are connected. The combined components of a timber frame.
Mortise: A notch, hole, or cut in a piece of wood into which a tenon is fit to join two timbers together. This is the female part of a joint.
Tenon: The cut end of a timber that fits into a mortise to join two pieces of timber together. This is the male part of a joint.
Dovetail: A mortise and tenon joint shaped like a dove’s tail.
Gusset: A metal plate attached to one or both sides of a joint to strengthen the joint.
There are, of course, many more timber frame terms. After all, this craft has been around for thousands of years. Do you think I missed any of the more important terms? Let me know!