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Timber framing (German: Fachwerkbauweise) and "post-and-beam" construction are traditional methods of building with heavy timbers, creating structures using squared-off and carefully fitted and joined timbers with joints secured by large wooden pegs. If the structural frame of load-bearing timber is left exposed on the exterior of the building it may be referred to as half-timbered, and in many cases the infill between timbers will be used for decorative effect. The country most known for this kind of architecture is Germany, where timber-framed houses are spread all over the country.^[1][2]

The method comes from working directly from logs and trees rather than pre-cut dimensional lumber. Hewing this with broadaxes, adzes, and draw knives and using hand-powered braces and augers (brace and bit) and other woodworking tools, artisans or framers could gradually assemble a building.

Since this building method has been used for thousands of years in many parts of the world, many styles of historic framing have developed. These styles are often categorized by the type of foundation, walls, how and where the beams intersect, the use of curved timbers, and the roof framing details.

Box frame

A simple timber frame made of straight vertical and horizontal pieces with a common rafter roof without purlins. The term box frame is not well defined and has been used for any kind of framing (with the usual exception of cruck framing). The distinction presented here is that the roof load is carried by the exterior walls. Purlins are also found even in plain timber frames.

Cruck frame

A cruck is a pair of crooked or curved timbers^[3] which form a bent (U.S.) or crossframe (UK); the individual timbers are each called a blade. More than 4,000 cruck frame buildings have been recorded in the UK. Several types of cruck frames are used; more information follows in English style below and at the main article Cruck.

• True cruck or full cruck: blades, straight or curved, extend from ground or foundation to the ridge acting as the principal rafters. A full cruck does not need a tie beam.
• Base cruck: tops of the blades are truncated by the first transverse member such as by a tie beam.
• Raised cruck: blades land on masonry wall, and extend to the ridge.
• Middle cruck: blades land on masonry wall, and are truncated by a collar.
• Upper cruck: blades land on a tie beam, similar to knee rafters.
• Jointed cruck: blades are made from pieces joined near eaves in a number of ways. See also: hammerbeam roof
• End cruck is not a style, but on the gable end of a building.

• 
  Half-timbered houses, Backnang, Germany
• 
  Half-timbered houses, Miltenberg im Odenwald, Germany
• 
  Rural old railway station timber framing style in Metelen, Germany

Aisled frame

Aisled frames have one or more rows of interior posts. These interior posts typically carry more structural load than the posts in the exterior walls. This is the same concept of the aisle in church buildings, sometimes called a hall church, where the center aisle is technically called a nave. However, a nave is often called an aisle, and three-aisled barns are common in the U.S., the Netherlands, and Germany. Aisled buildings are wider than the simpler box-framed or cruck-framed buildings, and typically have purlins supporting the rafters. In northern Germany, this construction is known as variations of a Ständerhaus.

Half-timbering

Half-timbering refers to a structure with a frame of load-bearing timber, creating spaces between the timbers called panels (in German Gefach or Fächer = partitions), which are then filled-in with some kind of nonstructural material known as infill. The frame is often left exposed on the exterior of the building.^[4]

Infill materials

The earliest known type of infill, called opus craticum by the Romans, was a wattle and daub type construction.^[5] Opus craticum is now confusingly applied to a Roman stone/mortar infill as well. Similar methods to wattle and daub were also used and known by various names, such as clam staff and daub, cat-and-clay, or torchis (French), to name only three.

Wattle and daub was the most common infill in ancient times. The sticks were not always technically wattlework (woven), but also individual sticks installed vertically, horizontally, or at an angle into holes or grooves in the framing. The coating of daub has many recipes, but generally was a mixture of clay and chalk with a binder such as grass or straw and water or urine.^[6] When the manufacturing of bricks increased, brick infill replaced the less durable infills and became more common. Stone laid in mortar as an infill was used in areas where stone rubble and mortar were available.

Other infills include bousillage, fired brick, unfired brick such as adobe or mudbrick, stones sometimes called pierrotage, planks as in the German ständerbohlenbau, timbers as in ständerblockbau, or rarely cob without any wooden support.^[7] The wall surfaces on the interior were often "ceiled" with wainscoting and plastered for warmth and appearance.

Brick infill sometimes called nogging became the standard infill after the manufacturing of bricks made them more available and less expensive. Half-timbered walls may be covered by siding materials including plaster, weatherboarding, tiles, or slate shingles.^[8]

The infill may be covered by other materials, including weatherboarding or tiles,^[8] or left exposed. When left exposed, both the framing and infill were sometimes done in a decorative manner. Germany is famous for its decorative half-timbering and the figures sometimes have names and meanings. The decorative manner of half-timbering is promoted in Germany by the German Timber-Frame Road, several planned routes people can drive to see notable examples of Fachwerk buildings.

Gallery of infill types:

• 
  Decorative fired-brick infill with owl holes
• 
  Ordinary brick infill left exposed
• 
  Stone infill called opus incertum by the Romans
• 
  Some stone infill left visible
• 
  The wattle and daub was covered with a decorated layer of plaster.
• 
  Like wattle and daub, but with horizontal stakes
• 
  Here, the plaster infill itself is sculpted and decorated.
• 
  Top: wattle and daub, bottom: rubblestone

Gallery of some named figures and decorations:

• 
  Simple saltires or St. Andrews crosses in Germany
• 
  Two curved saltires also called St. Andrews crosses during repairs to a building in Germany: The infill has been removed.
• 
  Several forms of 'man' figures are found in Germany; this one is called a 'wild man'.
• 
  A figure called an Alemannic woman
• 
  Wild man (center), half-man (at the corners)
• 
  Relief carvings adorn some half-timbered buildings.
• 
  The foot braces are carved with sun discs (Sonnenscheiben), a typical design of the North-German Weser-Renaissance.

The collection of elements in half timbering are sometimes given specific names:

• 
  Upper German Fachwerk (from 1582/83 in Eppingen BW)
• 
  An example of Fachwerk in Franconia (Fränkisches Fachwerk). Image:I, Metzner
• 
  Fachwerk in Upper Franconia often used to be detailed.
• 
  Close studding is found in England, Spain and France.
• 
  Square-panel half-timbering with fired brick infill: Square paneling is typical of the Low German house, and is found in England.
• 
  Cruck framing can be built with half-timber walls. This house is in the Ryedale Folk Museum in England.

History of the term

According to Craven (2019),^[9] the term:

was used informally to mean timber-framed construction in the Middle Ages. For economy, cylindrical logs were cut in half, so one log could be used for two (or more) posts. The shaved side was traditionally on the exterior and everyone knew it to be half the timber.

The term half-timbering is not as old as the German name Fachwerk or the French name colombage, but it is the standard English name for this style. One of the first people to publish the term "half-timbered" was Mary Martha Sherwood (1775–1851), who employed it in her book, The Lady of the Manor, published in several volumes from 1823 to 1829. She uses the term picturesquely: "...passing through a gate in a quickset hedge, we arrived at the porch of an old half-timbered cottage, where an aged man and woman received us."^[10] By 1842, half-timbered had found its way into The Encyclopedia of Architecture by Joseph Gwilt (1784–1863). This juxtaposition of exposed timbered beams and infilled spaces created the distinctive "half-timbered", or occasionally termed, "Tudor" style, or "black-and-white".

Oldest examples

The most ancient known half-timbered building is called the House of opus craticum. It was buried by the eruption of Mount Vesuvius in 79 AD in Herculaneum, Italy. Opus craticum was mentioned by Vitruvius in his books on architecture as a timber frame with wattlework infill.^[11] However, the same term is used to describe timber frames with an infill of stone rubble laid in mortar the Romans called opus incertum.^[12]

Alternative meanings

A less common meaning of the term "half-timbered" is found in the fourth edition of John Henry Parker's Classic Dictionary of Architecture (1873) which distinguishes full-timbered houses from half-timbered, with half-timber houses having a ground floor in stone^[13] or logs such as the Kluge House which was a log cabin with a timber-framed second floor.

Structure

Traditional timber framing is the method of creating framed structures of heavy timber jointed together with various joints, commonly and originally with lap jointing, and then later pegged mortise and tenon joints. Diagonal bracing is used to prevent "racking", or movement of structural vertical beams or posts.^[14]

Originally, German (and other) master carpenters would peg the joints with allowance of about 1 inch (25 mm), enough room for the wood to move as it 'seasoned', then cut the pegs, and drive the beam home fully into its socket.^{[citation needed]}

To cope with variable sizes and shapes of hewn (by adze or axe) and sawn timbers, two main carpentry methods were employed: scribe carpentry and square rule carpentry.

Scribing or coping was used throughout Europe, especially from the 12th century to the 19th century, and subsequently imported to North America, where it was common into the early 19th century. In a scribe frame, timber sockets are fashioned or "tailor-made" to fit their corresponding timbers; thus, each timber piece must be numbered (or "scribed").

Square-rule carpentry was developed in New England in the 18th century. It used housed joints in main timbers to allow for interchangeable braces and girts. Today, standardized timber sizing means that timber framing can be incorporated into mass-production methods as per the joinery industry, especially where timber is cut by precision computer numerical control machinery.

Jetties

A jetty is an upper floor which sometimes historically used a structural horizontal beam, supported on cantilevers, called a bressummer or 'jetty bressummer' to bear the weight of the new wall, projecting outward from the preceding floor or storey.

In the city of York in the United Kingdom, the famous street known as The Shambles exemplifies this, where jettied houses seem to almost touch above the street.

Timbers

Historically, the timbers would have been hewn square using a felling axe and then surface-finished with a broadaxe. If required, smaller timbers were ripsawn from the hewn baulks using pitsaws or frame saws. Today, timbers are more commonly bandsawn, and the timbers may sometimes be machine-planed on all four sides.

The vertical timbers include:

• posts (main supports at corners and other major uprights),
• wall studs (subsidiary upright limbs in framed walls), for example, close studding.

The horizontal timbers include:

• sill-beams (also called ground-sills or sole-pieces, at the bottom of a wall into which posts and studs are fitted using tenons),
• noggin-pieces (the horizontal timbers forming the tops and bottoms of the frames of infill panels),
• wall-plates (at the top of timber-framed walls that support the trusses and joists of the roof).

When jettying, horizontal elements can include:

• The jetty bressummer (or breastsummer), where the main sill (horizontal piece) on which the projecting wall above rests, stretches across the whole width of the jetty wall. The bressummer is itself cantilevered forward, beyond the wall below it.
• The dragon-beam which runs diagonally from one corner to another, and supports the corner posts above and supported by the corner posts below
• The jetty beams or joists conform t floor dimensions above, but are at right angles to the jetty-plates that conform to the shorter dimensions of "roof" of the floor below. Jetty beams are mortised at 45° into the sides of the dragon beams. They are the main constituents of the cantilever system, and determine how far the jetty projects.
• The jetty-plates are designed to carry the jetty beams. The jetty plates themselves are supported by the corner posts of the recessed floor below.

The sloping timbers include:

• Trusses (the slanting timbers forming the triangular framework at gables and roof)
• Braces (slanting beams giving extra support between horizontal or vertical members of the timber frame)
• Herringbone bracing (a decorative and supporting style of frame, usually at 45° to the upright and horizontal directions of the frame)

Post construction and frame construction

Historically were two different systems of the position of posts and studs:

• In the older (medieval) manner, called post construction, the vertical elements continue from the groundwork to the roof. This post construction in German is called Geschossbauweise or Ständerbauweise. It is somewhat similar to balloon framing method common in North America until the middle of the 20th century.
• In the advanced manner, called frame construction, each story is constructed like a case, and the whole building is constructed like a pile of such cases. This frame construction in German is called Rähmbauweise or Stockwerksbauweise and allows jettying.

Ridge-post framing is a structurally simple and ancient post and lintel framing where the posts extend all the way to the ridge beams. Germans call this Firstsäule or Hochstud.

Modern timber connector method (1930s–1950s)

In the 1930s a system of timber framing referred to as the "modern timber connector method"^[15] was developed. It was characterized by the use of timber members assembled into trusses and other framing systems and fastened using various types of metal timber connectors. This type of timber construction was used for various building types including warehouses, factories, garages, barns, stores/markets, recreational buildings, barracks, bridges, and trestles.^[16] The use of these structures was promoted because of their low construction costs, easy adaptability, and performance in fire as compared to unprotected steel truss construction.

During World War II, the United States Army Corps of Engineers and the Canadian Military Engineers undertook to construct airplane hangars using this timber construction system in order to conserve steel. Wood hangars were constructed throughout North America and employed various technologies including bowstring, Warren, and Pratt trusses, glued laminated arches, and lamella roof systems. Unique to this building type is the interlocking of the timber members of the roof trusses and supporting columns and their connection points. The timber members are held apart by "fillers" (blocks of timber). This leaves air spaces between the timber members which improves air circulation and drying around the members which improves resistance to moisture borne decay.

Timber members in this type of framing system were connected with ferrous timber connectors of various types. Loads between timber members were transmitted using split-rings (larger loads), toothed rings (lighter loads), or spiked grid connectors.^[17] Split-ring connectors were metal rings sandwiched between adjacent timber members to connect them together. The rings were fit into circular grooves on in both timber members then the assembly was held together with through-bolts. The through-bolts only held the assembly together but were not load-carrying.^[16] Shear plate connectors were used to transfer loads between timber members and metal. Shear plate connectors resembled large washers, deformed on the side facing the timber in order to grip it, and were through-fastened with long bolts or lengths of threaded rod. A leading manufacturer of these types of timber connectors was the Timber Engineering Company, or TECO, of Washington, DC. The proprietary name of their split-ring connectors was the "TECO Wedge-Fit".

Modern features

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 15 to 30 cm (6 to 12 in), while common wood framing uses many more timbers with dimensions usually in the 5- to 25-cm (2- to 10-in) 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 the traditional mortise and tenon or more complex joints that are usually fastened using only wooden pegs.^{[citation needed]} Modern complex structures and timber trusses often incorporate steel joinery such as gusset plates, for both structural and architectural purposes.

Recently, it has become common practice to enclose the timber structure entirely in manufactured panels such as structural insulated panels (SIPs). Although the timbers can only be seen from inside the building when so enclosed, construction is less complex and insulation is greater than in traditional timber building. SIPs are "an insulating foam core sandwiched between two structural facings, typically oriented strand board" according to the Structural Insulated Panel Association.^[18] SIPs reduce dependency on bracing and auxiliary members, because the panels span considerable distances and add rigidity to the basic timber frame.

An alternate construction method is with concrete flooring with extensive use of glass. This allows a solid construction combined with open architecture. Some firms have specialized in industrial prefabrication of such residential and light commercial structures such as Huf Haus as low-energy houses or – dependent on location – zero-energy buildings.

Straw-bale construction is another alternative where straw bales are stacked for nonload-bearing infill 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 to build.

Mudbricks also called adobe are sometimes used to fill in timber-frame structures. They can be made on site and offer exceptional fire resistance. Such buildings must be designed to accommodate the poor thermal insulating properties of mudbrick, however, and usually have deep eaves or a veranda on four sides for weather protection.

Engineered structures

Timber design or wood design is a subcategory of structural engineering that focuses on the engineering of wood structures. Timber is classified by tree species (e.g., southern pine, douglas fir, etc.) and its strength is graded using numerous coefficients that correspond to the number of knots, the moisture content, the temperature, the grain direction, the number of holes, and other factors. There are design specifications for sawn lumber, glulam members, prefabricated I-joists, composite lumber, and various connection types. In the United States, structural frames are then designed according to the Allowable Stress Design method or the Load Reduced Factor Design method (the latter being preferred).^[19]

History and traditions

The techniques used in timber framing date back to Neolithic times, and have been used in many parts of the world during various periods such as ancient Japan, continental Europe, and Neolithic Denmark, England, France, Germany, Spain, parts of the Roman Empire, and Scotland.^[20] The timber-framing technique has historically been popular in climate zones which favour deciduous hardwood trees, such as oak. Its northernmost areas are Baltic countries and southern Sweden. Timber framing is rare in Russia, Finland, northern Sweden, and Norway, where tall and straight lumber, such as pine and spruce, is readily available and log houses were favored, instead.

Half-timbered construction in the Northern European vernacular building style is characteristic of medieval and early modern Denmark, England, Germany, and parts of France and Switzerland, where timber was in good supply yet stone and associated skills to dress the stonework were in short supply. In half-timbered construction, timbers that were riven (split) in half provided the complete skeletal framing of the building.

Europe is full of timber-framed structures dating back hundreds of years, including manors, castles, homes, and inns, whose architecture and techniques of construction have evolved over the centuries. In Asia, timber-framed structures are found, many of them temples.

Some Roman carpentry preserved in anoxic layers of clay at Romano-British villa sites demonstrate that sophisticated Roman carpentry had all the necessary techniques for this construction. The earliest surviving (French) half-timbered buildings date from the 12th century.

Important resources for the study and appreciation of historic building methods are open-air museums.

Topping out ceremony

The topping out ceremony is a builders' rite, an ancient tradition thought to have originated in Scandinavia by 700 AD.^[21] In the U.S., a bough or small tree is attached to the peak of the timber frame after the frame is complete as a celebration. Historically, it was common for the master carpenter to give a speech, make a toast, and then break the glass. In Northern Europe, a wreath made for the occasion is more commonly used rather than a bough. In Japan, the "ridge raising" is a religious ceremony called the jotoshiki.^[22] In Germany, it is called the Richtfest.

Carpenters' marks

Carpenters' marks are markings left on the timbers of wooden buildings during construction.

• Assembly or marriage marks were used to identify the individual timbers. Assembly marks include numbering to identify the pieces of the frame. The numbering can be similar to Roman numerals except the number four is IIII and nine is VIIII. These marks are chiseled, cut with a race knife (a tool to cut lines and circles in wood), or saw cuts. The numbering can also be in Arabic numerals which are often written with a red grease pencil or crayon. German and French carpenters made some unique marks. (Abbundzeichen (German assembly marks)).
• Layout marks left over from marking out identify the place where to cut joints and bore peg holes; carpenters also marked the location on a timber where they had levelled it, as part of the building process, and called these "level lines"; sometimes they made a mark two feet from a critical location, which was then called the "two-foot mark". These marks are typically scratched on the timber with an awl-like tool until later in the 19th century, when they started using pencils.
• Occasionally, carpenters or owners marked a date and/or their initials in the wood, but not like masons left masons' marks.
• Boards on the building may have "tally marks" cut into them which were numbers used to keep track of quantities of lumber (timber).
• Other markings in old buildings are called "ritual marks", which were often signs the occupants felt would protect them from harm.

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