Whether you’re a first-time homeowner exploring timber framing or an architect specifying joinery for a commercial project, this reference is for you. Terms are organized A–Z with plain-language definitions grounded in traditional craft and modern practice.
In joinery, the point where the end of one timber meets the face or end of another. The quality of an abutment directly affects how cleanly a joint transfers load. See also: Butt Joint.
A hand tool with a curved blade mounted perpendicular to the handle, used to shape and smooth timbers. An adze leaves distinctive scalloped marks that are a prized visual characteristic of hand-hewn timber work.
A lengthwise volume in a timber-framed building, running parallel to the roof ridge. Most traditional structures are divided into a central aisle flanked by narrower side aisles. Compare: Bay.
In Dutch-style barn framing, the heavy transverse tie beam that connects the tops of the H-bent posts, typically secured with wedged through-tenons. It anchors the entire crossframe and resists outward thrust from roof loads.
A horizontal brace placed diagonally at the corner of a timber frame, typically at plate level, to resist the lateral force of the hip rafter.
A curved brace that rises from a post or wall to support a beam or rafter above it. Arch braces are both structural and visually dramatic — one of the most celebrated elements in traditional timber frame design.
The sharp edge formed where two flat surfaces of a timber meet. Arrises can be left sharp, chamfered for aesthetics, or used as a reference line for layout and joinery.
A short vertical timber connecting the foot of a rafter to a wall plate at the top of a masonry wall. It stiffens the lower roof plane and provides a solid bearing point for rafter loads.
A handled boring tool used to drill large-diameter holes in timber, typically for peg holes in mortise-and-tenon joinery. Traditional framers used hand-cranked augers; modern shops often use chain mortisers or drill press rigs.
A compressive or tensile force applied directly along a member’s central axis — the kind of load a post carries when supporting a beam directly overhead.
A decorative and protective board fixed along the sloping edge of a gable roof, covering the exposed ends of the purlins. Barge boards can be plain or elaborately carved. Also called: Rake Board.
The space between two adjacent bents or crossframes in a timber building, defining the structural rhythm of the frame. A three-bay barn has four bents dividing it into three equal spans. Compare: Aisle.
Any substantial horizontal timber whose primary role is to carry loads across a span and transfer them to supports such as posts or walls.
A large wooden mallet — typically 15 to 30 pounds — used to drive pegs and close stubborn joints without damaging the timber surface. Also called: Commander, Persuader.
The primary structural unit of a timber frame: a complete crossframe assembly — usually comprising posts, tie beam, rafters, and braces — that stands perpendicular to the ridge. Bents are typically assembled flat on the ground and raised into position as a unit on raising day.
Any angled cut made across the width or depth of a timber that is not a standard 90-degree angle. Bevels appear frequently in compound roof framing, hip and valley work, and decorative chamfering.
A heavier floor timber that spans between posts or walls and carries a series of lighter common joists, distributing floor loads to the frame’s primary structural members. Compare: Bridging Joist.
A notch cut at the lower end of a rafter — with a vertical plumb cut and a horizontal seat cut — that allows the rafter to sit squarely on the wall plate. One of the most common and important cuts in roof framing. Compare: Crowsfoot.
A scarf joint with a jagged, interlocking profile that resists both tension and compression. Used in heavy structural splices where a simpler joint would be insufficient. Also known as: Trait de Jupiter.
A timber frame type in which the roof trusses are supported entirely by the wall structure — posts, sills, tie beams, and plates. The dominant form of English and North American timber framing. Compare: Cruck Frame.
Any diagonal timber used to resist racking — the tendency of a rectangular frame to distort into a parallelogram under lateral load. See also: Knee Brace, Arch Brace.
A block or short timber tenoned or pegged to one member to provide additional bearing support for another. Common under post caps, at beam-to-post connections, and in decorative porch framing.
A common floor joist that spans between binding joists, carrying the floor deck. Lighter and more closely spaced than the binding joist below it. Compare: Binding Joist.
A wide-bladed axe with the edge beveled on one side only and fitted with an offset handle to clear the knuckles. The primary tool of the traditional timber hewer, used to flatten logs into square timbers.
A deliberate upward curve built into the top surface of a beam or lower chord of a truss to counteract the sag that will occur under load. A properly cambered beam settles to a level or slightly crowned position once loaded. Traditional guidance recommends 1 inch of camber per 20 feet of span.
A beam or structural member that extends horizontally beyond its last support, carrying load on the unsupported end. Cantilevered decks, overhanging upper stories (jetties), and forebay barns all rely on cantilever principles.
Incised marks cut into timbers during test assembly to uniquely identify each piece and its matching partner, allowing a disassembled frame to be accurately re-erected on site. Essential in scribe-rule framing. Also called: Assembly Marks, Marriage Marks.
A bevel cut along the long arris of a timber, removing the sharp corner. Chamfers can run straight through or end in a decorative “stop.” One of the simplest and most elegant finish details in timber framing.
A mortise elongated to allow a tenoned member to be swung in at an angle — useful for inserting braces or joists into an already-assembled frame where normal insertion would be impossible.
A surface crack that develops along the grain of a timber as it dries and the outer fibers shrink faster than the wet core. Checks are normal and expected in large timbers, do not typically affect structural performance, and are part of the natural character of solid-sawn wood.
In a truss, the major upper or lower member. The top chord (usually the principal rafters) resists compression; the bottom chord (the tie beam) resists outward thrust and carries tension.
A horizontal timber connecting a pair of opposing rafters partway up the roof, used to prevent the rafters from spreading outward or sagging at mid-span. Unlike a tie beam at wall level, a collar is elevated within the roof space.
A longitudinal roof member, regularly spaced in sets, that spans between principal rafters and directly supports the roof sheathing or roofing material. See also: Principal Purlin, Purlin.
One of a regularly spaced series of inclined roof members that carry the roof sheathing. In a heavy timber roof, common rafters are typically lighter than principal rafters and bear on purlins rather than directly on the wall plate. Compare: Principal Rafter.
A force that pushes the particles of a material together, tending to shorten it. Posts, struts, and the top chords of trusses are typically in compression.
A central vertical post in a roof truss that rises from the tie beam to the collar purlin above. A defining feature of medieval English roof framing, still used for its dramatic visual presence.
An ancient British timber frame type in which each crossframe is formed by a pair of curved timbers (blades) that rise from near ground level to the roof ridge, combining the functions of wall and rafter in a single sweeping member. Compare: Box Frame.
To cut a shallow housing or notch into a timber to receive another member; also the recess itself. Dapping is often used to seat the foot of a brace or secure a floor joist against lateral movement.
The permanent, static weight of a building’s own structure and fixed materials — timbers, roofing, floors, insulation, and finish materials. Dead load is constant and always present. Compare: Live Load.
The measurable bending or movement of a structural member under load. Some deflection is normal in all beams; engineers typically limit it to acceptable ranges such as L/360 of span for floor beams.
An angled shoulder cut on a tenon that provides maximum bearing area at a mortise-and-tenon connection while minimizing material loss in the mortised member.
A roofed structure that projects vertically from a sloping roof, typically housing a window. Dormers add light, headroom, and visual interest to upper floors.
Two tenons cut side-by-side on the end of a single wide or deep timber, increasing the bearing area of the joint and reducing the risk of splitting the mortised member.
A tenon shaped like a dove’s spread tail — wider at the end than the root — that interlocks with a corresponding mortise to resist pull-out forces. Self-locking in one direction and among the most elegant solutions in timber joinery.
A horizontal diagonal beam placed at a building corner to bisect the angle between two wall plates, carrying the foot of a hip rafter or the inner ends of corner joists.
A traditional joinery technique in which the peg hole in the tenon is deliberately offset slightly from the hole bored through the mortise. When the wooden peg is driven home, the offset draws the joint tightly together without clamps. Drawboring creates connections that improve with time.
A tie beam positioned below the top of the wall posts rather than at plate level, gaining additional clear height in the space below the roof trusses. Characteristic of certain Dutch and American barn styles.
The lower edge of a roof where it overhangs the wall below. Generous eaves keep rain away from walls and foundations and are a defining aesthetic element in timber frame homes, especially those with deep overhangs and exposed rafter tails.
In a framed overhang (jetty), a beam set outboard of the wall plane to form the base for the cornice and the bearing surface for the feet of common rafters above.
A timber specification that excludes the central pith of the log, allowing the timber to dry more evenly and with fewer checks. FOHC timbers are typically more dimensionally stable, though they require larger logs to produce.
A separate tenon piece — not integral to either timber — fitted into matching mortises in two members to join them. Free tenons allow complex multi-way connections that would be impossible to cut as a single piece. Also called: Loose Tenon, Spline.
An L-shaped steel measuring tool with two legs fixed at exactly 90 degrees (standard: 24-inch blade, 16-inch tongue). Its face carries rafter tables and conversion factors indispensable to timber framing layout. Also called: Steel Square, Rafter Square.
The most common roof form: two sloping planes meeting at a central ridge, creating triangular gable walls at each end. Simple to frame, structurally efficient, and the classic profile of most timber frame homes and barns.
A gable roof with each slope broken into two pitches — the lower slope steeper and the upper shallower. The gambrel maximizes usable loft space and is the traditional profile of the New England and Dutch barn.
A major spanning timber that supports a series of smaller floor joists, bridging between foundation walls, posts, or beams. Girders typically carry the heaviest floor loads in the building.
A horizontal timber that connects wall posts at a level between the sill and the plate. Wall girts run parallel to the ridge; bent girts run perpendicular. Girts stiffen the wall frame and often serve as the bearing point for floor joists.
Freshly cut timber that has not yet been dried or seasoned. Green wood is easier to work with hand tools and preferred by many traditional framers. Pegs driven into green frames tighten as the wood dries around them. Compare: Seasoned Wood.
A post wider and deeper at the top than at the bottom — the shape of an inverted gunstock — providing more wood for the complex joinery at the plate and girt connections. Typically cut from the base of a tapered log, inverted so the wider butt end is at the top. Also called: Jowled Post.
An end or crossing joint in which each of two timbers is reduced by half its depth over the joint area so the two pieces fit together flush. Commonly used where two horizontal members must cross at the same elevation.
A short horizontal timber projecting from the top of a wall, supported beneath by a curved brace and carrying a vertical hammer post above. Hammer beam roofs span great widths with relatively short individual timbers, producing soaring cathedral-like interior spaces.
A crossframe shaped like the letter H — two tall posts connected by a heavy tie beam — characteristic of Dutch-style three-aisle barn framing.
The dense, non-living inner wood of a tree, typically darker in color and more resistant to decay and insects than the surrounding sapwood. Heartwood of white oak, Douglas fir, and eastern white pine is prized for both durability and appearance.
In a hip or compound roof, the rafter that runs diagonally from a corner of the wall plate up to the ridge, forming the outer edge of the hip. Hip rafters carry load from two adjacent roof planes and require compound angle cuts for proper seating.
A roof with four sloping planes meeting at a ridge and no vertical gable walls. Offers excellent structural stability and a lower profile — ideal for exposed sites or where a quieter roofline is desired. Compare: Gable Roof.
A shallow notch or recess cut into a timber to receive the full cross-section of another member, providing positive bearing across the full surface rather than relying solely on the tenon for load transfer. Standard practice in quality timber framing. Also called: Dap, Box.
Material placed between the structural timbers of an exterior wall to provide weather enclosure and insulation. Historic infill materials included wattle-and-daub, brick nogging, and plaster; modern timber frames typically use structural insulated panels (SIPs) or stud-framed walls with spray foam or batt insulation.
Any rafter cut shorter than a full-length common rafter because it is interrupted by a hip, valley, or dormer. Jack rafters lie in the same pitch as the common rafters and require compound angle cuts where they meet the hip or valley rafter.
A cantilevered overhang of an upper floor or story that projects beyond the face of the wall below. In contemporary timber framing, jetties add visual depth, shadow, and articulation to a facade.
The craft of connecting timbers using precisely cut woodwork joints — mortises, tenons, dovetails, scarfs, and more — rather than metal fasteners. Joinery is the defining skill of the timber framer and the principal reason timber frames outlast all other construction types.
A relatively small timber, placed in a regularly spaced series, that supports a floor deck or ceiling. In timber framing, joists typically span between major beams or girders and are tenoned or housed into them at each end.
An enlargement near the top of a post, providing additional material for the cluster of joints — girts, plates, and braces — that converge at that point. See also: Gunstock Post.
The slot left in wood by the passage of a saw blade — slightly wider than the blade thickness due to the set of the teeth. Understanding kerf width is essential when laying out precise joinery cuts.
A small wedge-shaped element driven into a slot in a joint to lock it tightly and prevent movement. Used in tusk tenon connections, wedged scarfs, and wherever a joint must be tightened or made removable.
The central vertical member of a kingpost truss, rising from the midpoint of the tie beam up to the ridge and receiving the upper ends of both principal rafters. The simplest and most elegant of all roof truss forms. Compare: Queenpost.
A short diagonal timber connecting a post to a beam at right angles, stiffening the connection and resisting racking forces. Knee braces typically run at 45 degrees and are one of the most recognizable elements of timber frame design.
A joint in which two timbers overlap, each reduced in depth over the overlap zone so the combined depth remains constant. Used for lengthening (scarfs), crossing, and corner connections.
The process of marking joinery locations, dimensions, and reference lines on a timber before cutting. In scribe-rule framing, layout is done with timbers positioned together in the shop; in square-rule framing, from standardized reference lines on each piece independently.
A horizontal timber spanning a door or window opening, carrying the load of the wall or frame above it.
All variable, non-permanent loads on a structure — people, furniture, snow, wind, and seismic forces. Residential floor live loads are typically designed for 40 lbs per square foot. Compare: Dead Load.
Matching incised marks cut into adjacent timbers during test assembly to identify which piece belongs where, allowing the disassembled frame to be accurately re-erected on site. See also: Carpenter’s Marks.
A rectangular cavity cut into the face or end of a timber to receive a projecting tenon. The “female” half of the mortise-and-tenon joint — the most fundamental connection in all of timber framing. See also: Mortise-and-Tenon Joint.
The foundational joint of timber framing: the reduced end of one timber (the tenon) is inserted into a precisely cut cavity (the mortise) in another, then locked with wooden pegs through aligned holes in both members. A well-executed mortise-and-tenon distributes load across a large bearing surface and, when drawbored, becomes tighter as the wood dries.
Solid infill — traditionally brick, but sometimes stone, plaster, or modern insulation board — packed between the structural timbers in the exterior walls of a half-timbered building.
A lean-to addition or aisle appended to the side of a main building, typically with its own lower shed roof. Outshots expand the floor plan without altering the primary frame. Also called: Lean-to.
The horizontal projection of the roof beyond the face of the wall below. Generous overhangs protect walls and foundations from rain, shade windows in summer, and reveal rafter tails and purlin ends as celebrated structural details.
A cylindrical wooden pin — typically ¾ to 1 inch in diameter, made from a tough hardwood such as white oak or black locust — driven through aligned holes in a mortise-and-tenon joint to lock it permanently. The visible peg end, slightly proud of the timber surface, is one of the defining details of authentic timber framing. Also called: Treenail, Trunnel.
The most important longitudinal timber in a timber frame: the horizontal member that runs along the tops of the wall posts, tying the bents together and providing the bearing surface for the rafters. The plate simultaneously stabilizes the wall plane, the floor plane below, and the roof plane above. Also called: Top Plate, Wall Plate.
A vertical timber that transfers loads from the beams and roof above down to the sill, foundation, or floor structure below. Posts are the vertical anchors of the timber frame.
A broad structural category encompassing any system of vertical posts and horizontal beams. In common usage, “post and beam” often refers to a system where timbers are connected with metal fasteners rather than wood-to-wood joinery. True timber framing is a subset distinguished by its use of cut woodwork joints. See also: Timber Frame.
A lengthwise roof timber of substantial size, spanning between principal rafters and carrying common rafters above it. Principal purlins divide the rafter span into manageable segments. See also: Common Purlin, Purlin.
A large inclined rafter, typically placed directly over a principal post, that carries the purlins and common rafters of the roof system. Principal rafters form the top chords of roof trusses.
Any longitudinal timber in a roof frame that lies parallel to the ridge and transfers roof loads to the principal rafters or other primary supports. Purlins break up the rafter span and carry the roof sheathing between them. See also: Common Purlin, Principal Purlin, Ridge Purlin.
In a queenpost truss, one of a symmetrically paired set of vertical members rising from the tie beam toward the principal rafters and separated at their upper ends by a straining beam. Queenpost trusses work well for wide spans where a single central kingpost would be insufficient. Compare: Kingpost.
Any inclined roof member spanning some portion of the distance from eave to ridge, carrying the roof deck and its loads to the wall plates and tie beams below. See also: Common Rafter, Principal Rafter, Jack Rafter, Hip Rafter.
The act of erecting the prefabricated bents, roof trusses, and connecting timbers of a frame on the foundation. Modern timber frame raisings typically take one to three days with a small crane and crew. Seeing the full frame standing for the first time is one of the most memorable moments of the entire project. Also called: Rearing (UK).
The continuous longitudinal timber at the peak of a gable or hip roof, connecting the tops of all opposing rafters. Ridges are often cut to a non-orthogonal section to allow square connections with the angled roof geometry. Also called: Ridge Piece, Ridge Tree.
The slope of a roof surface, expressed as the vertical rise per horizontal foot of run. A “6-in-12 pitch” rises 6 inches for every 12 inches of run (26.6°). Pitch affects the visual character of a building, the volume of interior space, and the structural forces within the roof frame.
A structural assembly of timbers — typically two principal rafters, a tie beam, and one or more vertical and diagonal web members — that work together as a rigid unit to carry roof loads across a span. See also: Kingpost, Queenpost, Hammer Beam, Scissors Truss.
A lengthwise joint that splices two timbers end-to-end to produce a single longer member. Scarfs must transfer tension, compression, or both across the splice, and range from simple oblique cuts to elaborate locking profiles such as the Bolt-o’-Lightning.
A roof truss in which the lower chord members cross diagonally under the ridge rather than running level. The result is a vaulted interior ceiling that follows the roof pitch — one of the most dramatic spatial effects possible in timber framing.
A layout method in which each timber is custom-fitted to its actual neighbors as they will sit in the assembled frame. Joints are cut to match the real geometry of the individual timbers, producing perfectly fitted connections regardless of dimensional variations. The traditional method used throughout most of timber framing history. Compare: Square Rule.
Timber that has been air-dried or kiln-dried to a moisture content near equilibrium with its surrounding environment. More dimensionally stable than green wood and less likely to check, warp, or shrink after installation. Compare: Green Wood.
The horizontal timber at the base of the timber frame wall, resting directly on the foundation. The sill ties the bottoms of the posts together, anchors the frame to the foundation, and distributes post loads into the foundation below.
A modern building panel consisting of a rigid insulation core bonded between two structural skins of oriented strand board (OSB). SIPs are widely used in timber frame construction to enclose the exterior of the frame, providing a continuous insulation layer without thermal bridging. Fast to install and highly energy-efficient, they work particularly well with the large open bays of a timber frame.
A layout method in which joints are cut to a smaller, theoretically perfect “inner timber” imagined within each actual timber, regardless of surface variation. Square-rule timbers are largely interchangeable — a significant advantage in production framing. Compare: Scribe Rule.
A large primary floor timber that spans a major opening to carry a series of common joists. The word “summer” derives from the French “sommier” (pack animal) — the summer beam is the beast of burden of the floor system. See also: Girder.
The projecting tongue formed at the end of a timber by reducing its cross-section on two or more sides, leaving a shoulder that seats against the face of the mortised member. The “male” half of the mortise-and-tenon joint, typically secured with wooden pegs. See also: Mortise-and-Tenon Joint.
A force that pulls the particles of a material apart, tending to lengthen it. Tie beams, the lower chords of trusses, and certain brace connections are in tension.
A tenon that passes completely through the mortised timber and emerges on the opposite face, where it can be wedged, pinned, or locked with a key. The visible protruding end is a classic detail in exposed timber work.
A critical horizontal transverse timber that connects the tops of opposing wall posts or principal rafters, resisting the outward thrust that roof loads would otherwise impose on the walls. Among the most structurally important — and often the most visually prominent — timbers in the frame.
A large, squared or shaped piece of wood — generally 5 inches or larger in its smaller dimension — cut and prepared for use as a structural member. Above that threshold it is “timber” rather than “lumber,” carrying load in ways that dimensional lumber cannot, with surfaces that tell the story of the tree from which they came.
A structural system of large timbers connected by precision-cut woodwork joints — mortise and tenon, dovetail, scarf, and others — fastened with wooden pegs and supporting the smaller members to which roof, walls, and floors are attached. Distinguished from post-and-beam construction by the use of wood-to-wood joinery rather than metal connectors.
An end joint at the peak of a pair of rafters: one rafter cut to a central tongue, the opposing rafter cut to a two-pronged fork that straddles it. The interlocking geometry resists both lateral and rotational movement at the ridge without additional fasteners.
The traditional ceremony marking the placement of the last timber in a frame, often celebrated by fixing a bough or wreath to the topmost point. A moment of pride and gratitude for everyone who brought the frame to life.
A structural assembly of timbers arranged so that each member works primarily in either pure tension or pure compression, with little or no bending. This efficiency allows trusses to span distances impossible for any solid beam. See also: Roof Truss.
A through tenon with a projecting “tusk” or buttress on one face that provides additional bearing and prevents withdrawal when a wedge is driven alongside it. Commonly used to connect floor joists or beams to a carrying timber.
The topmost part of a jowled post in an English tying joint, where the post extends above the plate level to present the teazle tenon that secures the tie beam from above. The upstand locks the tie beam, plate, and post together into a single monolithic connection.
In a compound roof, the rafter that follows the inner line where two adjacent roof planes meet over an inside corner — the inverse of the hip rafter. Valley rafters collect water from both adjacent slopes and require compound angle cuts.
A compound roof formed where two roof slopes meet over an inside corner of a building, creating a valley between them. Common wherever a wing, ell, or addition joins a main structure at right angles. Compare: Hip Roof.
Describing a building style, method, or material tradition that is distinctly local — shaped by available materials, climate, cultural practices, and craft knowledge. Vernacular timber framing varied enormously by region and produced the rich diversity of traditional building forms we draw inspiration from today.
The natural rounded arris left on a timber where the sawyer followed the outer curve of the log rather than squaring the corner. Technically a defect but accepted in limited amounts; in rustic timber frames, wane can be celebrated as evidence of the timber’s origin in a real tree.
An ancient wall infill system: woven branches or sticks (the wattle) are interlaced between structural timbers and then plastered over with a mud, clay, and straw mixture (the daub). The standard infill for European timber frames for over a thousand years.
A diagonal brace in the plane of a roof or wall running between structural members specifically to resist lateral wind loads. Particularly important in long or tall structures where wind forces can be significant.