Timber framing is the method of creating framed structures of heavy
timber jointed together with pegged mortise and tenon joints.
Two principal historical layout methods used were: scribe carpentry
and square rule carpentry. In a scribe frame, each timber will only fit in
one place, so each timber has to be numbered. Square rule carpentry
developed in New England in the 18th century and feature housed
joints in main timbers to allow for interchangeable braces and girts.
Today, regularized wood can mean that timber framing is treated as
joinery, especially when large CNC machines cut timber.
The spaces between the timbers often were infilled with wattle and
daub, brick, or rubble. Plastered faces on the exterior and interior were
often "ceiled" with wainscoting for insulation and warmth. This method
of in filling the spaces created the half-timbered style, with the timbers
of the frame being visible both inside and outside the building.
Historically, the timbers would have been hewn square using a felling ax
and then finish surfaced with a broad ax. If required, smaller timbers
were rip sawn from the hewn using pitsaws or frame saws. Today it is
more common for timbers to be bandsawn, and the timbers may be
machine planed on all four sides.
Porch of a modern timber-framed house Here is a look at the interior of
a modern hand-hewn post and beam home.In the United States and
Canada, the art of timber-frame construction has been revived since
the 1970s and is now experiencing a thriving renaissance of the
ancient skills. This is primarily due to such practitioners as Steve
Chappell, Jack Sobon, and Tedd Benson, who studied old plans and
techniques and revived the technique that had been long neglected.
Once a hand crafted skill passed down, timber-frame construction has
now been modernized with the help of CNC machines. These tools have
helped the industry grow to where it is today, allowing for more
affordable frames and shorter lead-times for projects.
Timber-framed structures differ from conventional wood framed
buildings in several ways. Timber framing uses fewer, larger wooden
members. Commonly timbers in the range of 6" to 12", while common
wood framing uses many more timbers with dimensions usually in the 2"
to 10" range. The methods of fastening the frame members also differ.
In conventional framing, the members are joined using nails or other
mechanical fasteners, whereas timber framing uses mortice and tenon
or more complex joints that are usually fastened using only wooden
pegs. Modern complex structures and timber trusses often incorporate
steel joinery such as gusset plates. The steel is used for both
structural and architectural purposes.
It has become common to surround the timber structure entirely in
manufactured panels, such as SIPs (Structural Insulated Panels). This
method of enclosure means that the timbers can only be seen from
inside the building but has the benefits of being less complex to build
and offering more efficient heat insulation. Structural Insulated Panels
are a sandwich construction of two rigid composite materials usually
wood-based like OSB or plywood with a foamed insulating material in
between. This is accomplished by either by gluing or injecting foam in
place. Polyurethane and polyisocyanurate are the most common foam
used. The advantage of this for timber framing in the modern world
results in less of a dependency on bracing and auxiliary members. Joists
and rafters can be reduced as the panels can span a considerable
distance. Structural Insulated Panels significantly increase the stiffness
of the timber frame itself.
Alternative ways include the use of straw-bale construction. The straw
bales are stacked for the walls with various finishes applied to the
interior and exterior such as stucco and plaster. This appeals to the
traditionalist and the environmentalist as this is using "found" materials
Timber Frame & Post and Beam definitions.
AIR DRIED - stacking wood prior to installation to allow air movement to evaporate moisture for a prescribed period of
BRACE – a structural component, on a slope, used to secure other parts of the structure. May be permanent or
BAY – The space between two timber frame bents.
BEAM – a principal horizontal structural member, used to carry vertical loads.
BEAM POCKET – a notch in a wall prepared to receive the ends of a beam.
BENT – The structural network of timbers, in a wall or truss, making
up one cross sectional part of a timber frame.
BLIND MORTISE – a mortise that does not extend completely through the piece.
COLLAR PURLIN – horizontal, longitudinal beams that support collar ties.
COLLAR TIE – a horizontal log or timber between 2 adjacent rafters that prevent sagging and spreading of the roof
CROSS-GRAIN – deviation of grain direction from the longitudinal axis of a piece of wood or from the stem axis in a
DRAW BORING (DRAW-PINNING) – offsetting holes in a mortise and tenon joint, into which a
tapered pin is driven.
DRYING (AIR DRIED, KILN DRIED, SEASONED) – the condition or process defining the moisture content of wood; in
lumber grading, having a moisture content of no more than 19%.
EQUALIBRIUM MOISTURE CONTENT (EMC) – the moisture content eventually attained in wood exposed to a given
level of relative humidity and temperature.
FLITCH PLATE (KNIFEPLATE) – a metal plate cut into the center of a log or timber connections, bolted to the
components, in order to provide additional shear and tension strength.
FLY RAFTER – the end rafter on a roof overhang, typically on a gable end, that is supported by the ridge, trimmer,
and lookout rafters.
GIRDER – a horizontal beam carrying floor joists.
GIRT – a horizontal timber connecting 2 posts. Traditionally used for attaching vertical sheathing.
GREEN (LOGS) – freshly cut and unseasoned wood; having moisture content in excess of 19%.
GUSSET – the connectors used on truss work that provide strength to the joints. May be plywood, metal, boards, or
other materials of equal strength.
GUY WIRE – an anchored cable acting as a brace.
HANDCRAFTED LOG SYSTEMS – the craft of producing a structure from logs.
HEADER – horizontal member that spans over the top of an opening.
HOUSED MORTISE – a recessed mortise where bearing is provided for the entire tenoned member
KEYWAY –refers to the groove cut in the end grain at the side of a door or window opening. A wood or metal spline
(key) is inserted to stabilize the wall sections around the opening.
KILN-DRY WOOD – wood dried to constant weight in an oven maintained at temperatures of 101 to 105 degrees
KING POST – as part of a truss, the vertical post that extends from a horizontal member (chord, joist, girt, etc.) to the
peak; connected with the principal rafters.
KNEE BRACE – a diagonal brace, typically at a 45-degree angle between a post and a beam.
KNEEWALL – a short wall section; typically above the 2nd floor ending with a roof plate.
KNOT – a portion of a branch overgrown by the expanding girth of the bole or a larger branch; that area of the tree’s
stem that a branch grows out of; on smooth and planed surfaces appears as a hard round or oval shaped section.
LAP – a place or part where one log crosses over another.
LATHE – in log building a lathe type machine may be used for rough peeling of the bark or in the case of machine-cut
logs to shape the log to its finished form.
MOISTURE CONTENT – the weight of water in the cell walls and cavities of wood, expressed as a percentage of
MORTISE – a square or rectangular notch, slot, or hole cut into a structure component that will accept a corresponding
MORTISE AND TENON – a joint which a projection (tenon) on one end of a piece is inserted into a notch, slot or hole
(mortise) on another piece.
OUTRIGGER BEAM – a beam beyond or outside of the exterior wall that becomes the roof plate. Typically the supports
are the overhang or projection of gable and corresponding cross walls.
PEG– a 1” or larger, wooden dowel, typically made of Oak.
PURLIN – Horizontal roof beams, typically located between the plate and the ridge. Used to provide mid-span support
for the rafters.
SCARF –the cuts made on the sides of a log, at the location of a notch, as the receiving portion of a Saddle Notch.
SCARF JOINT – a joint made when notching and lapping two timbers.
SEASONED (SEASONING) - the act of drying wood to the etent that the moisture content has reached equilibrium with
the outdoor atmospheric humidity.
SPLINE – a piece placed in slot cuts, grooves, dados, etc. to strengthen joints between two components. Made of wood
or metal. In Log Building splines are typically used in openings tostabilize wall sections.
THROUGH-BOLTS – a threaded metal rod, extending the fullheight of a wall, fastened at each end with nuts and
washers. Used to provide rigidity, and the ability to tighten a wall section as settling occurs. Compression springs may
also be used to adjust for settling.
TIMBER FRAME – the methods of joining large timbers into a braced structural frame. At times referred to as Post and
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