Timber Frame Terms

8/15/2019 Timber Frame Terms

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Timber-FrameTerminology

BAY. For efficiency in both constructioneffort and material use, timber-framestructures are typically erected in boxlikesections, called bays, consisting of two

bents (one on each end) along withadditional frame members that connect the

bents and form the structure.

BEAM. Any horizontal timber.

BENT. ach bent forms an end-wall in a bay. !ike indi"idual slices in a bread loaf, bents extend completely through the

structure from one end to the other, andfrom the foundation base to the topmostridge, and ser"e as the ma#or load-bearingassemblies in a timber frame. $ents areusually built flat on the ground or floor deck, then raised to their "ertical positionwith a crane (or many willing hands).

CHAMFER. A %&-degree flat edge planed or routed along the outer, or 'leading, edges of a timber. Althoughchamfers are essentially decorati"e, theyare often placed where occupants maycome into contact with sharply cut,exposed timber angles and edges to

pre"ent in#ury.

GREEN TIMBER. ood used in timber framing is often built into a frame soonafter it is cut, when it is still 'green,without any intermediate drying period.*he #oinery used in such a frame isdesigned to tighten and become stronger

as this green wood dries and shrinks in theframework. +ometimes, timbers are air-dried in weather-protected enclosures toremo"e moisture and reduce them tonominal finished size, or kiln dried in aheated en"ironment to almost furniture-grade condition.

POST. Any "ertical timber.

RECLAIMED TIMBER. ood that issal"aged intact from older timber-frame

buildings such as barns, mills andfactories, and is then reused or recycledinto a new structure. wners often pay a

premium for the uni ue appearance andualities of aged or 'anti ue timbers.

TIMBER. According to standard lumber classifications, a timber is a length of solidwood with a cross-section greater thanfi"e inches on a side. ill construction, adesignation for fire code re uirements,calls for structural timbers cut to aminimum of eight inches per side.*imbers are used interchangeably as both

posts and beams in timber-frame buildings.

TRUNNEL. A large wood dowel or pegused as a fastener in wood #oinery. *heword is deri"ed from the descripti"e term'tree nail. /epending on the builder or owner0s prerogati"es, the exposed pegsare either cut off flat to the face of thetimbers or remain uncut to extend beyond

for a more rustic look.TRUSS. An arrangement of horizontaland "ertical timbers used to support aroof, upper floor or balcony. A trusscombines and multiplies the weight-

bearing strength of its indi"idual timbers,allowing the assembly to span a greater unsupported area and carry hea"ier loads.1arious types of roof truss designs area"ailable, including hammer beam andscissor trusses.

Construction Compon nts T rms

BEAM. Any horizontal timber.

BRACE. 1ariously called knee braces,angle braces or wind braces, these short,diagonally positioned timber supports are


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used as reinforcement in the corners of aframe to pre"ent shear, or horizontalmo"ement.

GIRT. *his critical frame componentforms a horizontal band, or 'girdle,completely around a timber frame. ftenreferred to as a girder, bent girt or girding

beam, it also ser"es as the base, or sill, for each upper floor and is fre uently used asthe outer support beam for indi"idual floor

#oists.

GUNSTOC! POST. Also known as a #owled post, this uni ue "ertical support isdimensionally wider at the top to enable itto form an intersection for multiple beamsand support members.

HAMMER BEAM. An elaborate type of tie beam used in 'open or unconnectedtrusses, often in con#unction with a cur"ed

brace, which helps to transmit the weightof a structure0s roof to the walls.

"OIST. *hese horizontal beamssimultaneously carry the weight of interior flooring and ser"e as room ceilingsupports. 2oists are supported by ma#or horizontal support members such as girtsand intermediary weight-bearing beamssuch as summer beams.

!ING POST. *his key timber forms thecenter point in a truss, or geometricsupport framework, and is often used asan intersection for other frame members.Although it is, technically speaking, a

post, it is usually suspended from abo"eand rarely extends to the floor of astructure.

PLATE. A beam that forms the horizontal base of the structure and ser"es as afoundation or attachment point for "erticalframe members such as posts and walls.

POST. Any "ertical timber.

PURLIN. *he upper sections of timber-frame bents are often connected andreinforced horizontally by purlins, whichalso support the roof deck.

#UEEN POSTS. *hese "ertical framemembers are used in a truss configuredwith two symmetrical posts instead of, or in addition to, a single king post.

RAFTER. 3oof-support timbers thatextend upward, from the wall plate to thetopmost ridge beam, are called rafters.3afters and purlins are sometimes used incombination. 4rincipal rafters form thesloping gable roof-line on each bent.

RIDGE. *his horizontal member,otherwise known as a ridge beam or ridge

plate, connects the bents at the apex of atimber-frame gable. 3idge beams are notalways re uired and may be omitted insome structures.

SUMMER BEAM. +ometimes referredto as a center girt, this beam is typicallyused to span large open areas and supportthe weight of other beams, such as #oistsat the center of a floor. $ecause it isre uired to bear considerable weight, it isoften the single largest wood componentin a timber-frame structure.

TIE BEAM. An auxiliary frame member,also known as a collar tie, it is installedhorizontally between roof rafters to

pre"ent a roof from spreading apart because of structural (weight) loading.

"oin r$ T rmsBIRDSMOUTH. A complex cut made atthe tail end, or bottom, of a rafter thatallows the timber to extend o"er and pastthe wall top plate, pro"iding a greater

bearing and attachment surface.


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BUTT. ne of the least complicated #oints, in which mating pieces are s uare-cut and simply butted against one another.$ecause this #oint has little inherentstrength and depends on gra"ity or

fasteners to remain in place, it is typicallylimited to intersections that are not sub#ectto mo"ement or strong opposing forces,such as where timber posts rest atophorizontal beams.

DO%ETAIL. A commonly used #oint thatincludes a fan-shaped tusk or tenon thatdrops into and interlocks in a similarlyshaped pocket cut. *he wedge-like shapeof this extremely strong #oint pre"ents theinterlocked timbers from shifting or separating from one another.

LAP. A #oint in which the ends of twotimbers are cut at matching angles andsimply o"erlaid, or 'o"erlapped, thenfastened to each other. $ecause the woodgrain direction of the mating pieces is

parallel, these #oints are easily concealedand often in"isible. !ap #oints aretypically used to extend, or lengthen,timbers in long horizontal runs.

MORTISE & TENON. A fre uentlyused #oint in timber framing, it includes amale end (tenon) cut onto the end of onetimber that fits into a s uare-cut matchingfemale receptacle (mortise). !ike manytimber frame #oints, it is often locked in

place by the addition of hardwood dowels,or pegs, called trunnels ('tree nails ).

POC!ET CUT. +imilar to a mortise, this #oint receptacle typically is 'open in twodimensions5 cut into the side or top face of a timber, it is designed to recei"e anidentically shaped tenon or tusk formed atthe end of a mating timber.

STEP'LAPPED RAFTER SEAT. Animpro"ed type of birdsmouth ando"erlapping #oint, it typically includes

complimentary cuts in the rafter and plateto resist downward and outward thrust, aswell as side-to-side mo"ement.

SPLINE. A long, relati"ely thin woodsection used to splice two timbers or reinforce a #oint. *he spline is typicallylayered between the timbers and theassembly is fastened through with wooddowels.

SHOULDER. A ledge cut into the face of a #oint5 this added facet increases a beam0sload-carrying capacity by transferringdownward force directly to the post whilethe #oint0s tenon resists the lateral load, or tension.

THROUGH "OINT. A descripti"e termused for #oints in which a tenon or tusk

passes completely through a mortise or pocket cut into the recei"ing timber.

TONGUE & FOR!. A specialized #ointoften used to connect the upper ends of rafters that meet to form a peak, or gable.

ne timber end is cut in an open 6-shapedconfiguration (the fork), and a singletongue formed on the intersecting timber closely fits into the space between the fork ends.

TUS!. A tenon-like extension formed atthe end of a timber that fits into amatching mortise or pocket cut5 this #ointtypically includes an additional shoulder or ledge cut into the outside face of the

#oint.

(EDGE. A wood shim inserted into a

#oint to tighten and lock the intersectingtimbers in place.

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Timber Frame Terms