Wood Frame Architecture

[Paskasi Coppola]

Timberframing (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.

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.

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.

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 Stnderhaus.

Half-timbering refers to a structure with a frame of load-bearing timber, creating spaces between the timbers called panels (in German Gefach or Fcher = 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]

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 stnderbohlenbau, timbers as in stnderblockbau, 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.

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 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]

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.

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]

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.

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.

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.

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".

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