Timber Frame Glossary

Timber framing can be confusing if you’re unfamiliar with the terminology used. Below is a list of terms related to the timber frame industry.

Common Timber Frame Terms

Adze: An axe-like tool with its blade at right angles to its handle, used to shape or dress timbers.

Anchor Beam: Major tying beam. Joined to post with shouldered through-tenon, wedged from the opposite side.

Anchor Bolt: A bolt protruding from the top of the foundation onto which the sill plate is fastened with a nut.

Auger: A tool for boring holes in wood.

Backfilling: Replacing excavated soil around a foundation.

Baseboard: Interior trim used on the wall of a room, along the floor.

Batten: A thin, narrow piece of lumber used for covering panel or siding edges.

Bay: Space between two bents.

Beam: A main horizontal member in a building’s frame.

Beam Pocket: A notch in a wall or receiving member prepared to receive the ends of a beam.

Beetle: A large wooden mallet typically weighing fifteen to twenty pounds. A maul.

Bent: Structural network of timbers or a truss that makes up one cross-sectional piece of the frame.

Bevel siding: Boards of varying width, tapering to a thin edge, and used as covering for sides of buildings.

Bleeding: An exudation of resin, gum creosote, or other substance from lumber.

Blind Mortise: A mortise that does not extend completely through the piece.

Blue Stain: A bluish discoloration, caused by certain fungi, which seldom penetrates beyond the sapwood, mostly Pine.

Bird’s Mouth: A V-shaped notch that resembles a bird’s open beak. It is cut into the base of a rafter and received by the plate.

Boring Machine: A hand-operated device with gears that drive an auger bit for boring large holes.

Board Foot: The quantity of lumber contained in (or derived from) a piece of rough, green lumber, 1 inch thick, 12 inches wide, and 1 foot long, or its equivalent in thicker, wider, narrower, or longer lumber.

Brace: Braces add rigidity to a frame. They typically run diagonally between posts and girts, and help prevent the frame from racking (leaning) in high winds. Braces are occasionally used in the horizontal plane, running from one girt to another.

Braced Frame: Timber frame.

Bressumer: English term for a beam supporting an upper wall of timber framing.

Bridging: Short pieces of wood placed between beams or joists to prevent lateral movement.

Broadaxe: A type of axe that has an unusually wide blade beveled only on one side, with an offset handle. Used to hew timbers from logs. A side axe.

Buck: Frame of dimensional lumber set into a log wall and used to frame windows and doors.

Buckling: Bending of a timber as a result of a compressive force along its axis.

Builder’s Risk Insurance: Insurance policy carried during construction that covers damage to home or property caused by fire, wind, theft or vandalism.

Building Code: Standards of construction designed to protect the health and safety of a home’s occupants.

Building Permit: Permit issued by a municipality that allows construction work on a specific site to go forward according to approved plans. Ensures that all proposed construction work meets building code and is added to the tax rolls.

CAD (Computer Aided Design): Software technology we use for all aspects of design with the possible exception of preliminary sketching.

Cant: A triangular strip of lumber, which is made by ripping a square timber diagonally.

Cantilever Beam: A projecting timber that supports an overhang.

Casing: Lumber used as interior trim around window and door frames.

Carrying Sticks: Sticks placed under a timber to provide an easy hand hold for carrying. Typically, two carrying sticks and four people are needed to carry a timber in this way.

Chamfer: A simple bevel done for embellishment of a timber.

Checks: Separation of wood fibers following the direction of the rays. Caused by the tension of uneven drying.

Circular Saw: Power saw with circular saw blade.

Clear: Lumber almost completely free from blemishes, defects or knots.

Coarse: As applied to the grain of lumber, that which has unusually wide growth rings for the species.

Collar Purlin: Horizontal longitudinal beam supporting collar ties.

Collar Tie: Horizontal connector between a pair of rafters used to reduce sagging or spreading of rafters.

Combination Square: A tool that can be used to lay out 45-degree or 90 degree angles. The stop is adjustable along the blade for use as a depth gauge.

Come-Along: A hand-operated ratchet winch. Used for pulling joints together, as a safety tie when raising a bent, and for pulling the frame together during the raising.

Common Rafters: Closely and regularly spaced inclined timbers that support the roof covering. Independent of bent system (see principal rafters).

Compression: Caused by a pressing or crushing type of force.

Conduction: A movement of heat through a material.

Convection: The transference of heat by circulation or movement.

Corner Chisel: A heavy-duty L-shaped chisel struck with a mallet. Used for cleaning out corners of a mortise.

Cope: A circular-arc notch cut on the tension face of a bending member adjacent to the members bearing surface to reduce shear stress parallel to the grain notch.

Cost-Plus: Type of contract made between a general contractor and a home owner that stipulates the owner will pay for the cost of building materials as the project progresses, plus an added percentage for the general contractor’s fee. This type of contract is opposite of a fixed-price contract.

Crosscut Saw: Saw designed to cut across the grain.

Crown of Timber: Convex side of timber.

Crown Post: Central vertical post of a roof truss that connects the bent plate or girt to the collar tie or collar purlin.

Cruck: Primitive truss formed by two main timbers, usually curved, set up as an arch or inverted V. Each half of the cruck is called a blade, and a pair is often cut from the same tree.

Crushing: A compressive failure. Permanent deformation resulting from compression.

D-Log: A profile you can choose for milling log home timbers. Named for its shape, each log is milled round on the outside and cut flat on the inside, resulting in a traditional log home look outside with a straight log wall on the inside.

Dead Load: Weight of building (roof, floors, walls, etc.).

Demurrage: Additional fees charged by the transportation company to cover delays in delivering a product.

Depth: The vertical thickness of a beam.

Design Agreement: Outlines the process of designing your new timber frame home.

Diagonal Grain: Grain that is other than parallel to the length of a timber. This will greatly reduce the strength of a timber.

Dimensional Lumber: Planed lumber that is sold according to its nominal size.

Disc Sander: Circular-action power sander.

Dormer: A dormer is a structural element of a building that protrudes from the plane of a sloping roof surface. Dormers are used to create usable space in the upper level of a building by adding headroom and usually also by enabling the addition of windows.

Douglas Fir: Douglas fir has a complex grain structure and is less prone to checking and twisting. Common to the Northwest, this wood species shows extraordinary structural strength and flexibility. In addition, Douglas fir is readily available in a wide variety of sizes and diameters for your home.

Dovetail: A tenon that is shaped like a dove’s spread tail to fit into a corresponding mortise.

Dowell: A cylindrical wooden pin used for holding two pieces of wood together.

Draw Boring: Intentional offsetting of holes in a mortise and tenon joint such that the joint is drawn tight during peg installation.

Draw Knife: A knife blade with handles on both ends that allow the knife to be pulled by both hands toward the user.

Dress: To plane one or more sides of a piece of sawn lumber.

Drift Hook: Drift pin.

Drift Pin: Used to pin joints temporarily when test-assembling a frame.

Drop: Ornamental pendant. The tear-shaped termination to the lower ends of the second-story post of a framed overhang. Also known as a pendill.

Dutchman: A timber patch to cover defect, previous joinery, or other blemish or error. Color and grain matching make them hard to find.

Eased-Edged: A piece of wood slightly rounded or “bull nosed” on each edge.

Eave: That part of a roof, which projects beyond the face of a wall.

Edge Distance: The distance from the center of a peg hole to the edge of the member, measured perpendicular to the grain direction.

Edge Grain: Lumber that is sawn along a radius of the annual rings or at an angle less than 45 degrees to the radius is edge-grained; this term is synonymous with “quarter sawn.”

Egress: A unit (door, window or skylight) from which people may exit the building. Local egress code requirements vary.

End Distance: The distance from the center of a peg hole to the end of the member, measured parallel to the grain direction.

End Match: To tongue-and-groove (T&G) the ends of lumber.

Equilibrium moisture content: The moisture content at which wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature.

Excessive Bending and Deflection: Values of allowable bending of timbers within a frame that have been established by building codes. Anything greater than these values is considered excessive.

Face Side: The side of a piece of wood or timber that shows the best quality.

Fiber Failure: Failure from tension in the lower fibers of a timber.

Flashing: Weatherproofing strips formed from metal, which channel water in a specific way. Step flashing is a series of short flashings that are layered between courses of roofing. Counter flashing is a piece of flashing that covers step flashings if no siding exists, such as at a log wall. Head flashing covers a window or door unit.

Flat Grain: Plain sawn or sawn tangential to the annual rings, as opposed to edge-grain or quarter sawn.

Framing Chisel: A heavy-duty chisel typically with a one-and-one-half to two-inch-wide blade. Designed to be used with a mallet.

Framing Square: Also called a steel square. An L-shaped metal tool used for laying out joinery. It has a body twenty-four inches long and two inches in width, and a tongue sixteen inches long and two inches in width.

Flutes: Hollows or grooves cut longitudinally for ornamental purposes.

Full-Width Notch: A notch on the tension or compression face of a bending member that extends across the full width of the face.

Furring: Any flat piece of lumber used to bring an irregular framing to a flat surface; in particular, a narrow strip of lumber, which is nailed to rafters, studding, and joists as backing.

Gable Roof: A double-sloping roof that forms an A-shape.

Gambrel Roof: A double-pitched roof with the lower slope steeper than the upper slope.

Gas Filled Window: Insulating glass units with a gas other than air in the air space; to decrease the unit’s thermal conductivity “U value” (see U value)

General Contractor: A professional who oversees a construction project, including the scheduling, supervision and payment of subcontractors.

Girder: Major timber that spans between sills.

Girt: Major horizontal timber that connects posts.

Glaze: To fit a window frame with glass.

Glulam: An engineered support beam made up of laminations of dimension lumber that have been glued together.

Grain: A term used with reference to the arrangement or direction of the wood elements (spiral grain, cross grain, etc.) and to the relative width of the growth rings (coarse grain, fine grain, etc.) It is also used to designate the angle of the growth rings in relation to the axis of the board (edge grain, flat grain).

Green Lumber: Unseasoned or wet lumber; lumber in which free water still remains within cells; lumber which has a moisture content above the fibre saturation point (approximately 25 to 30%).

Green Wood: Wood freshly cut that is not dried or seasoned.

Grilles: A decorative grid installed on or between glass panes, that does not actually divide the glass.

Gunstock Post: A post wider at the top than the bottom. The wider portion provides more wood for intersecting joinery.

Half Dovetail: A dovetail tapered only on one side.

Half Lap: A joint in which the two timbers are lapped or let-in to each other.

Half-Timbered Frame: An ancient building system in which the space between the timbers is filled with brick, plaster, or wattle and daub, so that the timbers are revealed to the exterior and to the interior of the building. The wattle was a framework of woven withes covered by layers of daub consisting of clay, lime, horsehair, and cow dung.

Halving: The removal of half the depth of two timbers in order that they may cross each other. A half lap.

Hammer Beam: A roof bracket projecting from the top of the wall that supports a roof truss. The design creates a large span with relatively short timbers.

Hand-Peeled: The process of removing the bark and outer layer (cambium) of a log. Hand peeling is usually done using a drawknife, although some companies use machines to achieve a hand-peeled look.

Hardwood: Wood of certain deciduous trees, e.g., oak, maple, ash, etc.

Header: Built-up horizontal member of a home’s frame that tops a window or doorway.

Heartwood: The inner layers of wood which in the growing tree have ceased to contain living cells, as opposed to the sapwood, which contains growing cells. Heartwood is generally darker in color than sapwood, though in some species the difference is scarcely perceptible.

Herringbone bracing: a decorative and supporting style of frame, usually at 45° to the upright and horizontal directions of the frame.

Hewn: Cut with an axe or an adze. (also called hand hewn)

Hip: A hip is the angled ridge formed by two adjoining planes.

Hold-Down Rod: A metal rod that provides extra anchorage of the roof system to the logs. These are desirable in high wind areas.

Horizontal Timbers: sill-beams, noggin-pieces, wall-plates.

Hook Pin: Drift pin.

Housed Mortise: A recessed mortise in which bearing is provided for the entire width of the tenoned member.

Housing: The shallow mortise or cavity for receiving the major part of a timber end. Usually coupled with a smaller deep mortise to receive a tenon for typing the joint.

Jamb: The side of a window, door, or other such opening.

Jetty: An upper floor that depends on a cantilever system in which a horizontal beam, the jetty bressummer, on which the wall above rests, projects forward beyond the floor below.

Joinery: The art or craft of connecting timbers using woodworking joints.

Joint: The connection of two or more timbers.

Joists: Small, parallel timbers that complete the floor frame.

Kerf: The groove formed in wood while being sawn or the thickness of the wood removed as sawdust.

Kerfing: Either a series of cuts with a circular saw set at a desired depth to remove a section of wood or the hand-sawing along the shoulder of an assembled joint to improve the fit of the joint.

Keyway: A joint between the footing and foundation wall.

Kiln: A heated chamber for drying lumber.

Kiln-Dried Lumber: Lumber, which has been seasoned in a dry kiln, usually, though not necessarily, to a lower moisture content than that of air seasoned lumber.

King Post: A central, vertical post extending from the bent plate or girt to the junction of the rafters.

Knee Brace: A small timber that is framed diagonally between a post and a beam.

Layout: The drawing of a joint on a timber before it is cut.

Lean-to: A shed section of a building that is framed into the main frame.

Live Load: Weight due to occupancy of building (people, furnishings, etc.).

Load: Weight.

Mallet: A hardwood hammer weighing from one and one-half to two and one-half pounds. Used for driving a chisel.

Maul: Beetle.

Maximum Allowable Fiber Stress in Bending: Safe design standard for fiber stress.

Maximum Allowable Horizontal Shear Stress: Safe design standard for shear stress.

Modulus of Elasticity: A measure of rigidity of a material. The ratio of stress (force per area) to strain (deformation).

Moment: The product of force times distance from which it acts. This causes a beam to bend.

Moment of Inertia: A property that reflects the strength of a timber dependent upon the size and shape of its cross section.

Mortise: A groove or slot into which or through which a tenon is inserted.

  • Open mortise – a mortise which has only three sides.
  • Stub mortise – a shallow mortise, depth depends on the size of the timber; also a mortise that does not go through the workpiece (as opposed to a “through mortise”).
  • Through mortise – a mortise which passes entirely through a piece.
  • Wedged half-dovetail – a mortise where the back is wider, or taller, than the front, or opening. The space for the wedge initially allows room for the tenon to be inserted, the presence of the wedge, after the tenon has been engaged, prevents its withdrawal.
  • Through wedged half-dovetail – a wedged half-dovetail mortise which passes entirely through the piece.

Mortise-and Tenon Joint: Any joint in which a projection on one end of a timber is inserted into a groove or slot in another timber.

Noggin-Pieces: The horizontal timbers forming the tops and bottoms of the frames of infill-panels.

Nominal Size: Undressed dimension of lumber. For example, lumber with a nominal size of two inches by four inches will have an actual size of about one and one-half inches by three and one-half inches.

Overall Length: Total length of timber including length of tenons on either end.

Overhang: Projection of second story beyond the first.

Partial-Width Notch: A notch on the tension or compression face of a bending member that does not extend across full width of the face.

Peg: A wooden dowel one to one and one-half inches in diameter, usually of oak or locust.

Pike Pole: A long pole pointed with a sharpened spike used for raising frames. These tools were known as early as the fifteenth century, when they were called “butters.”

Pin: Small peg.

Plates: Major horizontal timbers that support the base of the rafters.

Plumb: Vertical.

Post: Vertical or upright timber.

Post-and-Beam: Timber frame.

Power Hand Planer: A hand-held planer with rotating cutting blades. Used for finishing surfaces of rough-sawn timbers.

Principal Rafters: A pair of inclined timbers that are framed into a bent.

Purlins: Horizontal timbers that connect rafter trusses.

Pythagorean Theorem: For a right triangle, the sum of the squares of the sides is equal to the square of the hypotenuse. Used in calculating rafter and knee-brace lengths.

Queen Post: A pair of vertical posts of a roof truss standing on the bent plate or girt and supporting the rafters or collar tie.

Rack: The action of straining or winching a frame to bring it into square or plumb.

Rafter Feet: The lower ends of the rafters that are framed into the plate.

Rafter Peak: The point where the tops of the rafters meet.

Raising the Frame: Erecting the bents and roof trusses and joining and pegging the other timbers to the frame.

Reaction: A force pushing up in response to a load.

Rearing the Frame: English term. Equivalent to “raising the frame.”

Relish: The material between a peg or wedge hole and the end of a tenon or spline.

Ridgepole: A horizontal timber at the peak of the roof to which the rafters are attached.

Rip: To saw a board lengthwise.

Rip Saw: Saw designed to cut parallel to grain.

Roof Pitch: Inches of rise per foot of run. For example, a 45-degree roof has twelve inches of rise for each foot of run and is therefore called a “twelve pitch” roof.

Roof Truss: A structure to support the roof.

Router: A power tool with rotating cutting blades used in timber framing for rounding or embellishing edges of timbers.

Saddle Notch Corner: A saddle notch is an overlapping, interlocking type of log corner. A saddle notched corner ensures a tight fit and superior structural quality.

Sash: The framed casement part of a window in which the glass is fixed.

Scarf: A joint for splicing two timbers, end to end.

Scribe: To mark a timber by scratching a line with a sharp instrument; also to cut or shape a timber so that it fits the somewhat irregular surface of another.

Seasoned Wood: Dried wood.

Shakes: Separation of wood fibers that follow the curvature of the growth rings. Normally occurs during growth of the tree.

Shear Failure: Failure from shearing along the fibers of a timber.

Shearing: A force causing slippage between layers

Sheathing: The covering of boards or the waterproof material on the outside wall of a house or on a roof.

Shed Roof: A roof sloping in one direction.

Shim: Thin tapered pieces of material such as a shingle. Used for leveling sill timbers.

Shoulder of Timber: Point of intersection at the joint of two assembled timbers. Refers to timber with tenon.

Shoulder-To-Shoulder Length: Length of timber between the shoulders of the two end joints. (The overall length minus length of end tenons.)

Sill Timbers: Horizontal timbers that rest upon the foundation.

Slick: A chisel with a blade two and one-half or more inches in width. It is pushed by the hands instead of being struck with a mallet.

Sloping Timbers: Includes trusses, braces, and herringbone bracing.

Soffit: The underside part of a building such as under a roof overhang.

Softwood: Wood primarily of a conifer or evergreen, e.g., pine, spruce, Douglas fir, etc.

Span: The shoulder-to-shoulder distance.

Specific Gravity: The ratio of a material’s density versus the density of water.

Spline (aka: Free Tenon): A lumber or engineered wood element placed in slot cuts, grooves, dados, etc. to strengthen joints between components.

Splits: Complete separation of wood fibers.

Squaring Off: The process of drawing and cutting off one end of a timber so that the cut gives a plane surface perpendicular to the timber’s length.

Stand-Alone Timber Frame: A timber fame structure designed to resist loads without the use of shear walls or supplementary structural systems.

Summer Beam: Major timber that spans between grits or plates.

Template: A full-size pattern of thin material for laying out and checking joints.

Temporary Bracing: Method of temporarily adding rigidity to a frame during the raising.

Tenon: The projecting end of a timber that is inserted into a mortise.

  • Stub tenon – a short tenon; depth depends on the size of the timber; also a tenon that is shorter than the width of the mortised piece so the tenon does not show (as opposed to a “through tenon”).
  • Tusk tenon – a kind of mortise and tenon joint that uses a wedge-shaped key to hold the joint together
  • Through tenon – a tenon which passes entirely through the piece of wood it is inserted into, being clearly visible on the back side
  • Teasel tenon – a term used for the tenon on top of a jowled or gunstock post, which is typically received by the mortise in the underside of a tie beam. A common element of the English tying joint.
  • Top tenon – the tenon which occurs on top of a post.
  • Feather Tenon – a round shouldered machined fillet or feather which is glued into a machine-made (router) slot or mortise on each side of the joint.

Tension: A force causing the tendency of extension. In timber framing, captured tension adds rigidity and strength.

Through Tenon: A tenon that passes through the timber it joins. It may extend past the mortise and be wedged from the opposite side.

Timber: A large squared or dressed piece of wood ready for fashioning as one member of a structure.

Timber Frame: A frame of large timbers, joined and pegged together, supporting small timbers to which roof, walls, and floors are fastened. Same as braced frame.

Tongue and Fork: A type of joint in which one timber has the shape of a two-prong fork and the other a central tongue that fits between the prongs.

Transit: A telescope set on a tripod used for leveling foundation or sill timbers.

Trunnel or Treenail: A peg. Sometimes refers to an extra-large peg.

Truss: Assemblage of timbers forming a rigid framework. Example: A bent

Vertical Timbers: Include posts (main supports at corners and other major uprights)and studs (subsidiary upright limbs in framed walls).

Walking Beams: Two parallel beams laid on the ground used to assist moving timbers with a pivoting action.

Wall-Plates: At the top of timber-framed walls that support the trusses and joists of the roof.

Water Level: A flexible tube with glass ends, filled with water. Used for leveling foundation or sill timbers. A substitute for a transit.

Wedge: A tapered wood element with rectangular cross section used to secure through-tenons, through-splines and scarf joint.

Western Red Cedar: Characteristics – redwood, character grains and knots, and more resistant to insect infiltration.

Western White Wood: Characteristics – light wood, visible knots, and offers flexibility in staining options, from light to dark.

Width: The horizontal thickness of a beam, or thickness of a post.

Wind Brace: English term. Equivalent to knee brace.