Glossary of Oak

Framing

So you’ve had a visit from an oak framing company and they talked about details of your proposed building and you didn’t like to ask what a Bressumer was. Here’s a glossary of terms to help you out. To be fair, many of the larger oak frame companies employ sales staff and it’s most likely they don’t know what a Bressumer is either

A

• Arcade: A series of arches supported by columns or piers, often found in larger hall-style oak frames. • Ashlar (or Ashlar Block): Refers to finely dressed and cut stone, but in the context of timber framing, can sometimes refer to the vertical posts that rise from the top of the wall plate to support rafters in a roof space. • Axed: A term referring to timber that has been shaped or dressed with an axe.

B

• Bay: A repeated structural unit in a building, defined by a pair of posts and the beams that connect them, forming a section of the frame. Buildings are often described by the number of bays (e.g., a 3-bay barn). • Beam: A horizontal structural timber supporting loads. Can be primary (e.g., tie beam, principal rafter) or secondary (e.g., common joists). • Bent: A complete cross-sectional frame or 'slice' of the building, made up of posts, beams, and possibly braces, which is then lifted into place during erection. • Birdsmouth: Also commonly called a bird's beak cut, is a type of woodworking joint primarily used in roof framing to connect a sloping rafter to a horizontal wall plate (the top timber of a wall). It's named for its distinctive shape, which resembles an open bird's mouth or beak. • Brace: A diagonal timber used to stiffen a frame, resist racking (lateral movement) and transfer loads. o Knee Brace: A short diagonal brace connecting a post to a beam at an angle. o Curved Brace: A brace cut from a naturally curved piece of timber, often aesthetically pleasing. • Breasting Beam: A horizontal beam that runs parallel to the main wall in an infill or panel system. • Bressumer Beam: A large, horizontal timber beam (also spelled breastsummer or bressummer) that supports the weight of a wall or superstructure above an opening, such as a window or door.

C

• Camfer (or Chamfer): A decorative bevelled edge or corner cut off a timber. • Camber: The slight upward curve given to a beam to counteract anticipated deflection or sagging under load. • Carpenter's Marks (or Roman Numerals): Traditional numbering or marking system carved into timbers to indicate their position and jointing sequence during assembly. Essential for accurate frame erection. • Cleat: A small block of wood or metal fastened to a timber to support another member or prevent slipping. • Collar Beam: A horizontal timber connecting two opposite rafters at a point usually above the wall plate, forming a triangular bracing unit. • Common Rafters: The smaller, more closely spaced rafters that run from the wall plate up to the ridge, supporting the roof covering. They sit on or are notched into purlins and the ridge board. • Cruck Frame: A very old form of timber framing (distinct from box-frame) where large, naturally curved timbers (crucks) extend from ground level to the ridge, forming a complete arch-like roof support. • Blade (Cruck Blade): One of the curved timbers that forms a cruck. • Cross Frame: Similar to a bent, a structural frame running across the width of a building.

D

• Dovetail Joint: A strong, interlocking joint with a fan-shaped tenon and corresponding mortise, used to resist pulling apart and often for connecting tie beams to wall plates. • Dragon Beam: A diagonal timber that sits on wall plates in a corner, often supporting a jetty or an angled bay. • Dutch Hip (or Barn Hip): A part hipped roof

E

• Eaves: The part of a roof that projects beyond the walls of a building. • Erection: The process of assembling and raising the timber frame on site.

F

• Feather Edge: A type of timber cladding where boards are thicker on one edge and thinner on the other, overlapping to shed water. • Footing: The lowest part of a foundation, typically wider than the wall it supports, to distribute the load over a larger area. • Frame: The skeletal structure of the building, made up of interconnected timbers.

G

• Gable: The triangular upper part of a wall at the end of a pitched roof. • Gable Post: A vertical timber at the end of a gable, supporting the ridge and purlins. • Girt (or Girt Beam): A horizontal timber connecting posts, often used to define floor levels or wall sections. • Green Oak: Timber that has recently been felled and has not been seasoned (dried) before use. It has a high moisture content, which allows it to be cut easily but will shrink and develop characterful shakes (cracks) as it dries in situ.

H

• Header: A short beam or joist that supports other framing members that have been cut to create an opening (e.g., for a window or fireplace). • Housing: A joint where a portion of one timber is recessed into another, providing support and preventing lateral movement. Not a full mortise and tenon.

I

• Infill Panel: The material used to fill the spaces between the timbers of an oak frame, such as wattle and daub, brick, glass, or modern insulated panels (e.g., SIPs).

J

• Jettied (or Jetty): An upper floor or section of a building that projects out beyond the face of the floor below, often supported by exposed joists or beams. • Joist: A horizontal timber that supports a floor or ceiling. • Joint: The connection between two or more timber members. • Mortise and Tenon: The most fundamental and common joint in timber framing. A projecting 'tenon' (tongue) on one timber fits into a recessed 'mortise' (hole) on another, often secured by a wooden peg. • Lap Joint: A simple joint where one timber overlaps another.

K

• King Post: A vertical post that extends from the centre of a tie beam up to the apex of a roof truss, supporting the ridge or purlins.

L

• Lath: Thin strips of wood used to provide a backing for plaster or render, or to hold roof tiles/slates. • Ledger: A horizontal timber attached to a wall or beam to support joists.

M

• Mortise: The “Female” part of a Mortise & Tenon joint.

P

• Pantile: An S-shaped clay roof tile, common in East Anglia due to Dutch influence. • Peg: A hardwood dowel (usually oak) driven through a mortise and tenon joint to secure it. • Post: A vertical structural timber, typically supporting beams or trusses. • Principal Rafters: The main rafters in a roof truss, which are larger and more widely spaced than common rafters, supporting purlins. • Purlin: A horizontal timber running along the length of the roof, spanning between principal rafters or gables, and supporting the common rafters.

Q

• Queen Post: One of two vertical posts that rise from a tie beam to support a collar beam in a roof truss.

R

• Rafter: An inclined timber supporting the roof covering. See "Common Rafters" and "Principal Rafters." • Ridge (or Ridge Board): The horizontal timber at the apex of a pitched roof, where the tops of the rafters meet. • Riven: Timber that has been split along the grain rather than sawn, often used for shingles or cleft oak fencing.

S

• Scarf Joint: A method of joining two timbers end- to-end to create a longer member, often used for long wall plates or tie beams. Various forms exist (e.g., bladed, tabled). • Scribe: To mark and cut a timber to fit precisely against an irregular surface or another timber. • Seasoned Timber: Timber that has been air-dried or kiln-dried to reduce its moisture content, making it more stable and less prone to movement. Less common for primary oak frames due to cost and difficulty in working. • Shake: A natural crack or split in timber, often along the grain, caused by the drying process (especially in green oak). These are generally benign structurally in a well-designed frame. • Sill (or Ground Sill/Sole Plate): A horizontal timber that forms the base of a wall frame, resting on the foundation. Crucial for frame stability. • SIPs (Structural Insulated Panels): Pre-fabricated insulated panels used to enclose the oak frame, creating a highly energy-efficient and airtight building envelope. • Sole Plate: See "Sill." • Soffit: The underside of an architectural element, such as an arch, beam or eaves. • Spline: A thin strip of wood inserted into grooves in two adjoining pieces to strengthen a joint. • Spud: A small, specialized chisel used for trimming and cleaning out mortises. • Squint: An angled joint or corner. • Stud: A vertical timber in a wall, usually smaller than a main post, used for infill panels or non-load-bearing partitions. • Stretcher: A timber laid horizontally within a wall.

T

• Tenon: The “male” part of a mortise & tenon joint. • Tie Beam: A horizontal timber in a roof truss that connects the feet of two opposing principal rafters, preventing them from spreading outwards and pushing the walls apart. • Truss: A rigid framework of timbers, typically triangular, used to support a roof or bridge a span (e.g., King Post Truss, Queen Post Truss).

W

• Wall Plate (or Eaves Beam): A horizontal timber that sits on top of a wall, supporting the ends of the rafters or joists. • Wattle and Daub: A traditional infill material made from woven hazel or willow branches (wattle) coated with a mixture of clay, sand, straw and animal dung (daub).