1.
Purlin
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In architecture, structural engineering or building, a purlin is any longitudinal, horizontal, structural member in a roof except a type of framing with what is called a crown plate. In traditional timber framing there are three types of purlin, purlin plate, principal purlin and common purlin. A purlin plate in construction is also called an arcade plate in European English, under purlin. The term plate means a major, horizontal, supporting timber, purlin plates are beams which support the mid-span of rafters and are supported by posts. By supporting the rafters they allow longer spans than the rafters alone could span thus allowing a wider building, purlin plates are very commonly found in large, old barns in North America. A crown plate has similarities to a purlin plate but supports collar beams in the middle of a framed building. Principal purlins in wood construction, also called major purlin, side purlin, principal purlins are supported by principal rafters and support common rafters in what is known as a double roof. S. Example is known, ) are captured by a collar beam, through purlins are further categorized as trenched, back, or clasped, butt purlins are classified as threaded, tenoned, and/or staggered. Common purlins in wood construction, also called a major-rafter minor-purlin system, common purlins are typically trenched through the top sides of principal rafters and carry vertical roof sheathing. Common purlin roofs in North America are found in areas settled by Englishmen, no examples of framed buildings with common purlin roofs have been reported in England, however some stone barns in England have vertically boarded, common purlin roofs. Historically, these roofs are found in New England, the highest concentration in Maine, one of the oldest extant examples is in the Coffin House in Newbury, Massachusetts from 1678. The purpose of a purlin roof may be they allow a board roof. In steel construction, the term typically refers to roof framing members that span parallel to the building eave. The purlins are in turn supported by rafters or walls, purlins are most commonly used in Metal Building Systems, where Z-shapes are utilized in a manner that allows flexural continuity between spans. Section designations can be regional and even specific to a manufacturer, in steel building construction, secondary members such as purlins and girts are frequently cold-formed steel C, Z or U sections, C sections. Cold formed members can be efficient on a weight basis relative to mill rolled sections for secondary member applications, additionally, Z sections can be nested for transportation bundling and, on the building, lapped at the supports to develop a structurally efficient continuous beam across multiple supports. Information on the origin of the term purlin is scant, the Oxford Dictionary suggests a French origin, with the earliest quote using a variation of purlin in 1447. Note, The sketches in this section reference terminology commonly used in the UK, girt Joist Roof construction Timber roof trusses This article incorporates text from a publication now in the public domain, Chisholm, Hugh, ed. article name needed
2.
Post in ground
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Post in ground construction, also called earthfast or hole-set posts, is a type of construction in which vertical, roof-bearing timbers, called posts, are in direct contact with the ground. They may be placed into excavated post holes, driven into the ground, Earthfast construction is common from the Neolithic period to the present and is used world-wide. Post-in-the-ground construction is called an impermanent form such as for houses which are expected to last a decade or two before a better quality structure can be built. Post in ground construction can also include sill on grade, wood-lined cellars, most pre-historic and medieval wooden dwellings were built post in ground worldwide. This type of construction is believed to be an intermediate form between a palisade construction and a stave construction. Because the postholes are easily detected in archaeological surveys, they can be differentiated from the other two, post-in-ground was one of the timber construction methods used for French colonial structures in New France specifically called poteaux-en-terre. The Japanese also used earthfast construction they call Hottate-bashira until the eighteenth century, some places the people still use post in ground construction such as the Toguna shelter of the Dogon people in Africa. In the historical region of New France poteaux-en-terre was a style of earthfast timber framing. This method is similar to poteaux-sur-sol but for the boulin planted in the ground rather than landing on a sill plate. The spaces between the boulin were filled with bousillage or pierrotage, French colonization of the Americas Old Spanish Fort. Genevieve, Missouri Stilt house EARTHFAST ARCHITECTURE IN EARLY MAINE Earthfast Architecture at the Association for the Preservation of Virginia Antiquities
3.
Wall plate
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A plate or wall plate is a horizontal, structural, load-bearing member in wooden building framing. A plate in timber framing is A piece of Timber upon which some considerable weight is framed. Hence Ground-Plate. Window-plate. The terms sole plate or sill plate are used for the members at the bottom of a wall at the foundation but are most often just called a sole or sill without the word plate. Other load bearing timbers use the plate but are not in the wall such as crown plate, a purlin-like beam carried by crown posts in roof framing. In platform framing there are three types of plates and are located at the top and bottom of a wall section. Each type continues in a piecewise fashion around the perimeter of the structure. Sill plates — a lower plate which is bolted or strapped securely to the top of a foundation wall or concrete slab. These hold the house down against heavy winds, normally, J-bolts are placed in the curing concrete after the mason levels the foundation and finishes dressing the concrete or anchor bolts are drilled into the concrete foundation. Newer systems of galvanized strapping with a J-bolt like anchor placed in the concrete allows the builder to avoid the mating step of drilling the sill plates for the bolts, on an upper story, the lower wall plate is nailed to the platform of the supporting floor. The supporting platform is being supported by the studs of the even lower walls below. A second layer of lumber is always fastened to the top plates of the erected walls so that no joints overlap. In North America this is known as a top plate. The MMC Glossary 2008 - The Modern Construction Glossary of MMC, canadian Wood Council - Wood building design tools, case studies and references. How Your House Works House Framing and Structure overview, USDA Forest Products Laboratory Lists of Publications Wood handbook—Wood as an engineering material Design and Construction of Low Energy Houses in Saskatchewan
4.
Eaves
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The eaves are the edges of the roof which overhang the face of a wall and, normally, project beyond the side of a building. The eaves form an overhang to throw water clear of the walls and may be decorated as part of an architectural style. Eaves is derived from Old English efes meaning edge, according to the Oxford English Dictionary, eaves is both the singular and plural form of the word. However, the Merriam-Webster website lists the word as eave and states that it is used in plural. The word was used before the 12th century in the form efes, the primary function of the eaves is to keep rain water off the walls and to prevent the ingress of water at the junction where the roof meets the wall. The eaves may also protect a pathway around the building from the rain, prevent erosion of the footings, the eaves overhang may also shelter openings to ventilate the roof space. Aesthetic, traditional or purely decorative considerations may prevail over the functional requirements of the eaves. At the gables the eaves may extend beyond the end wall by projecting the purlins and are usually capped off by bargeboards to protect the wall. Eaves must be designed for wind speeds as the overhang can significantly increase the wind loading on the roof. Chhajja Eavesdrip Eavesdropping Gargoyle Lookout Rainhead Soffit Media related to Eaves at Wikimedia Commons
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Wood
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Wood is a porous and fibrous structural tissue found in the stems and roots of trees, and other woody plants. It is a material, a natural composite of cellulose fibers which are strong in tension embedded in a matrix of lignin which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, in a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots, Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber. In 2005, the stock of forests worldwide was about 434 billion cubic meters. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy, in 1991 approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction, a 2011 discovery in the Canadian province of New Brunswick discovered the earliest known plants to have grown wood, approximately 395 to 400 million years ago. Wood can be dated by carbon dating and in species by dendrochronology to make inferences about when a wooden object was created. People have used wood for millennia for many purposes, primarily as a fuel or as a material for making houses, tools, weapons, furniture, packaging, artworks. Constructions using wood date back ten thousand years, buildings like the European Neolithic long house were made primarily of wood. Recent use of wood has changed by the addition of steel. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the climate at that time. This process is known as growth, it is the result of cell division in the vascular cambium, a lateral meristem. These cells then go on to form thickened secondary cell walls, composed mainly of cellulose, hemicellulose, if the distinctiveness between seasons is annual, these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent, if the bark of the tree has been removed in a particular area, the rings will likely be deformed as the plant overgrows the scar. It is usually lighter in color than that near the portion of the ring. The outer portion formed later in the season is known as the latewood or summerwood. However, there are differences, depending on the kind of wood
6.
Truss
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In engineering, a truss is a structure that consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object. A two-force member is a component where force is applied to only two points. In this typical context, external forces and reactions to those forces are considered to act only at the nodes and result in forces in the members that are either tensile or compressive. For straight members, moments are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes, as is necessary for the links to be two-force members. A planar truss is one all members and nodes lie within a two dimensional plane, while a space truss has members and nodes that extend into three dimensions. The top beams in a truss are called top chords and are typically in compression, the beams are called bottom chords. The interior beams are called webs, and the areas inside the webs are called panels, Truss derives from the Old French word trousse, from around 1200, which means collection of things bound together. The term truss has often used to describe any assembly of members such as a cruck frame or a couple of rafters. One engineering definition is, A truss is a single plane framework of individual structural member connected at their ends of forms a series of triangle to span a large distance, a truss consists of typically straight members connected at joints, traditionally termed panel points. Trusses are typically composed of triangles because of the stability of that shape. A triangle is the simplest geometric figure that will not change shape when the lengths of the sides are fixed, in comparison, both the angles and the lengths of a four-sided figure must be fixed for it to retain its shape. The joint at which a truss is designed to be supported is commonly referred to as the Munter Point, the simplest form of a truss is one single triangle. This type of truss is seen in a roof consisting of rafters and a ceiling joist. Because of the stability of this shape and the methods of used to calculate the forces within it. The traditional diamond-shape bicycle frame, which utilizes two conjoined triangles, is an example of a simple truss, a planar truss lies in a single plane. Planar trusses are used in parallel to form roofs and bridges. The depth of a truss, or the height between the upper and lower chords, is what makes it an efficient structural form, a solid girder or beam of equal strength would have substantial weight and material cost as compared to a truss. For a given span, a deeper truss will require less material in the chords, an optimum depth of the truss will maximize the efficiency
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