timber frame joints


Barefaced Dovetail: Dovetail flared only on one edge, suitable for mortising as well as housing.

Barefaced Tenon: Tenon flanked by only one shoulder.

Bird's Mouth: A 90 degree notch (V-shaped) that resembles a bird's open beak. It is cut into the base of a rafter and received by the plate.

Butt Joint: The point where two timbers meet without penetration, kept in place by gravity or other timbers or ironwork.


Carpenter’s Marks: Incised matching marks at joints to identify uniquely matching parts in a frame, made during test assembly; indispensable to scribe rule method of layout. Other carpenter’s marks may identify all members of one crossframe or wall assembly.

Cheek: The broad surface of a tenon, the corresponding surface of a mortise.  The tenon shoulder is usually square to its cheek.

Compound Joinery: Connections whose timbers are cut at non orthogonal angles on both face and edge, typically found in hip and valley roofs.

Crowsfoot: 1.Notch cut into lower edge of rafter to fit outside upper corner of plate (Birdsmouth). 2.V-shaped mark indicating reference point or line in layout.


Daisy Wheel: Compass-drawn form in building geometry comprising equal-diameter intersecting circles, useful to determine proportions of building. Symbols of uncertain meaning occasionally found carved into south-facing beams and associated with the sun (day’s eye).

Diminished Shoulder: Angled shoulder found at certain mortise and tenon connections to provide good bearing and least material loss in the housing, while offering cutting advantages.

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

Drawbore: Traditional fastening technique in which the peg hole in the tenon is deliberately offset from the peg hole in the mortise to draw a joint tight when assembled and fastened with a tapered pin.


English Tying Joint: The end of a base–tied truss over a jowled post, wherein the foot of the principal rafter is tenoned to the top of the tie; the tie is simultaneously mortised to the teazle tenon on the jowl of the post and lap-dovetailed over the top of the plate; and the plate is mortised over a second tenon formed in the outward part of the jowled post.

Free Tenon/Spline: Tenon cut as a separate piece and used, via appropriate mortises, to join two timbers face to face, end to end or end to face.


Half Dovetail: A dovetail tapered only on one side.

Half Lap: End joint or crossing, in which the two timbers are lapped or let-in to each other to half their depths.

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

Haunch, Haunched Tenon: Retained part of a tenon that would otherwise be removed to fit a closed mortise at the end of a timber.  Haunch, which may be diminished, fits a groove and helps preserve alignment of the members without unduly weakening the end of the mortise.

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 tying the joint.


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

Joint: The connection of two or more timbers.

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

Jowl: Local step or flare near end of post or beam to accommodate joinery.


Key: Small element, usually wedge-shaped, used to lock a joint or, if a shear key, to prevent sliding of one member over another.

Keyed Beam: Two or more beams laminated together with cross grain keys let in between the beams to prevent slippage during bending.


Lap-Dovetail Joint: Dovetail housing cut into the surface of one timber to receive a dovetail tenon formed on the end of another. 

Lap Joint: Similar to the half-lap joint, but the parts are not necessarily housed to half their depths.

Layout: 1.Outlining joint on a timber before it is cut. 2.Arranging timbers in a determined pattern for marking.


Marriage Marks: Marks incised in a timber to indicate its proper placement in the frame when matched to identical marks on an adjoining timber.  By extension, any marking system to aid assembly or reassembly of individually fitted joints.

Miter: Equal division of the angle formed by two intersecting members; the act of dividing the angle.

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

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.


Notched Lap Joint: Lap joint with interference surface cut to prevent withdrawal of the tenon, found in very early braces.


Peg: A wooden dowel one to one and one-half inches in diameter, usually of oak or other tough wood; used toTimber Frame Pegs fasten timber joints, particularly the mortise and tenon joint (pegs shown to the right & below).

Timber Frame Pegs


Rabbet: Open (one sided) groove cut at an arris.

Reference Face: Surface of a timber chosen to measure from joint or frame layout, often the top of a beam or the outside of a post.

Relish: 1.In a mortise cut near the end of a timber, material the width and depth of the mortise remaining between the mortise-end and the end of the timbers. 2.In a tenon, material between the peg hole and the end of the tenon, equal in cross-section to the path of the peg through the tenon.


Scantling: 1.The cross-section of a timber as found in a table of scantlings together with length. 2.Any small piece of wood.

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

Scotch: 1.Slight surface cut or gash, especially a score made to keep tally; line on the ground in the game of hopscotch. 2.Shallow, angled notch in which a shore is fitted to lift or hold a building during raising or repairs.

Scribe: In general, to mark a timber by scratching a line with a sharp instrument; specifically to use dividers to transfer a profile to be cut – often irregular – from one surface to another.

Scribe Rule: General term for layout systems where each timber is custom-mated to its neighbors. The process requires setting out all the timbers for a given assembly in a framing yard or on a floor, positioned relatively as they will rest in the building. Plumb and level references are essential to most methods.

Shear Block: Wood block dapped partially to adjoining parallel laminae in a built-up chord, designed to resist shear between the two members or to transfer load around a discontinuity such as a scarf, and properly oriented parallel to the grain so that the shear block end grain bears upon chord end grain.

Shear Key: Wood block oriented perpendicular to (across) the grain.  Easier to assemble and can be tightened if wedged-shaped, but not as resistant to compression as a shear block.

Shoulder: 1.In a mortise and tenon joint, the element of tenoned member usually perpendicular to the tenon cheek and which lies against the face of the mortised member, there can be as few as one and as many as four shoulders on the tenoned member. When a shoulder angles back as it rises from a tenon cheek, it’s said to be diminished. When it angles forward, it’s said to be sallied. 2.In a housing, the lower bearing surface.

Soffit Tenon: Single-shouldered horizontal tenon with lower cheek coincident with bottom surface of beam.

Square Rule: Layout system in which a smaller, perfect timber envisioned within a rough outer timber and joints cut to this inner timber.  Many timbers in a square rule frame are interchangeable (the same).

Squaring Off: Cutting off one end of a timber to yield a plane surface perpendicular to the length; helpful for layout and revealing flaws in the timber.

Stub Tenon: Tenon that stops within the timber it joins.


Table: In a scarf joint, the raised portion of each scarf-half, designed to interfere once assembled and so prevent withdrawal in the length.

Template: Full-size pattern of thin material used for laying out and checking joints.

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

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

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. Usually found at rafter peaks.

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

Tusk Tenon: 1.Horizontal through tenon with outside wedge (the tusk) applied vertically. 2.Horizontal blind tenon with square buttress (the tusk) between lower cheek and shoulder. 3.Horizontal blind tenon with diminished buttress (the tusk) between upper cheek and shoulder. This buttress is sometimes called a diminished haunch because of its resemblance in profile to that of a diminished-haunched tenon. The latter tenon, however, is used to make a corner joint, whereas the tusk tenon is used to connect the end of one beam to the face of another.


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TimberhArt Woodworks (formerly Acorn Timber Frames)
L. Daniel and Kimberley Reagan
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