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.
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
4.
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
5.
Gambrel
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A gambrel or gambrel roof is a usually symmetrical two-sided roof with two slopes on each side. The upper slope is positioned at an angle, while the lower slope is steep. This design provides the advantages of a roof while maximizing headroom inside the buildings upper level. The name comes from the Medieval Latin word gamba, meaning horses hock or leg, the term gambrel is of American origin, the older, European name being a curb roof. Europeans historically did not distinguish between a gambrel roof and a roof but called both types a mansard. The cross-section of a roof is similar to that of a mansard roof. A gambrel roof overhangs the façade, whereas a mansard normally does not, gambrel is a Norman English word, sometimes spelled gambol such as in the 1774 Boston carpenters price book. Other spellings include gamerel, gamrel, gambril, gameral, gambering, cambrel, cambering, butchers gambrels, later made of metal, resembled the two-sloped appearance of a gambrel roof when in use. Gambrel is also a term for the joint in the part of a horses hind leg. In 1858, Oliver Wendell Holmes, Sr. Websters Dictionary also confusingly used the term hip in the definition of this roof, the term is also used for a single mansard roof in France and Germany. In Dutch the term two-sided mansard roof is used for gambrel roofs, the origin of the gambrel roof form in North America is unknown. The oldest known gambrel roof in America was on the second Harvard Hall at Harvard University built in 1677, possibly the oldest surviving house in the U. S. with a gambrel roof is the c. Note that the oldest surviving framed house in America, the Fairbanks House, has an ell with a gambrel roof, in Indonesia, they saw dwellings with a roof style where the end of a roof started as a hip and finished as a gable end at the ridge. The gable end was an opening, to smoke to dissipate from the cooking fires. This roof design was brought back to Europe and the American Colonies, and adapted to local conditions
6.
Mansard roof
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A mansard or mansard roof is a four-sided gambrel-style hip roof characterized by two slopes on each of its sides with the lower slope, punctured by dormer windows, at a steeper angle than the upper. The steep roof with windows creates a floor of habitable space. The upper slope of the roof may not be visible from street level when viewed from close proximity to the building, the earliest known example of a mansard roof is credited to Pierre Lescot on part of the Louvre built around 1550. This roof design was popularized in the early 17th century by François Mansart and it became especially fashionable during the Second French Empire of Napoléon III. Mansard in Europe also means the attic space itself, not just the roof shape and is used in Europe to mean a gambrel roof. Two distinct traits of the mansard roof – steep sides and a double pitch – sometimes lead to it being confused with other roof types. Since the upper slope of a roof is rarely visible from the ground. The gambrel roof style, commonly seen in barns in North America, is a cousin of the mansard. Both mansard and gambrel roofs fall under the classification of curb roofs. However, the mansard is a hip roof, with slopes on all sides of the building. French roof is used as a synonym for a mansard but is also defined as an American variation of a mansard with the lower pitches nearly vertical. In France and Germany, no distinction is made between gambrels and mansards – they are both called mansards, in the French language, mansarde can be a term for the style of roof, or for the garret living space, or attic, directly within it. The mansard style makes use of the interior space of the attic. Often the decorative potential of the Mansard is exploited through the use of convex or concave curvature, one frequently seen explanation for the popularity of the mansard style is that it served to shelter its owners against taxes as well as rain. Later examples suggest that either French or American buildings were taxed by their height to the base of the roof and this last explanation is the nearest to the truth, a Parisian law had been in place since 1783, restricting the heights of buildings to 20 metres. The height was measured up to the cornice line, making any living space contained in a mansard roof exempt. A1902 revision of the law permitted building three or even four stories within such a roof, the style was popularized in France by architect François Mansart. Although he was not the inventor of the style, his extensive and prominent use of it in his designs gave rise to the mansard roof
7.
Hip roof
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A hip roof, hip-roof or hipped roof, is a type of roof where all sides slope downwards to the walls, usually with a fairly gentle slope. Thus a hipped roof house has no gables or other vertical sides to the roof, a square hip roof is shaped like a pyramid. Hip roofs on houses could have two sides and two trapezoidal ones. A hip roof on a plan has four faces. They are almost always at the pitch or slope, which makes them symmetrical about the centerlines. Hip roofs often have a consistent level fascia, meaning that a gutter can be fitted all around, Hip roofs often have dormer slanted sides. Hip roofs are more difficult to construct than a gabled roof, Hip roofs can be constructed on a wide variety of plan shapes. Each ridge is central over the rectangle of the building below it, the triangular faces of the roof are called the hip ends, and they are bounded by the hips themselves. The hips and hip rafters sit on a corner of the building. Where the building has a corner, a valley makes the join between the sloping surfaces. They have the advantage of giving a compact, solid appearance to a structure, in modern domestic architecture, hip roofs are commonly seen in bungalows and cottages, and have been integral to styles such as the American Foursquare. However, the hip roof has been used in different styles of architecture. A hip roof is self-bracing, requiring less diagonal bracing than a gable roof, Hip roofs are thus much better suited for hurricane regions than gable roofs. Hip roofs have no large, flat, or slab-sided ends to catch wind and are much more stable than gable roofs. However, for a region, the roof also has to be steep-sloped. When wind flows over a shallow sloped hip roof, the roof can behave like an airplane wing, lift is then created on the leeward side. The flatter the roof, the more likely this will happen, a steeper pitched hip roof tends to cause the wind to stall as it goes over the roof, breaking up the effect. If the roof slopes are less than 35 degrees from horizontal, greater than 35 degrees, and not only does wind blowing over it encounter a stalling effect, but the roof is actually held down on the wall plate by the wind pressure
8.
Dormer
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A dormer is a roofed structure, often containing a window, that projects vertically beyond the plane of a pitched roof. Dormers are commonly used to increase the space in a loft. The term dormer is commonly used to refer to a dormer window although a dormer doesnt necessarily have to contain a window, a dormer is often one of the primary elements of a loft conversion. As a prominent element of many buildings, different types of dormer have evolved to complement different styles of architecture, when the structure appears on the spires of churches and cathedrals, it is usually referred to as a lucarne. Some of the different types of dormer are, Gable fronted dormer, Also called simply a gabled dormer, this is the most common type. It has a pitched roof of two sloping planes, supported by a frame that rises vertically to form a triangular section below the roofline. It is also known as a dog-house dormer, hip roof dormer, Also called a hipped dormer, it has a roof composed of three sloping planes that rise from each side of the dormer frame and converge at the ridge—analogous to the hip roof. Flat roof dormer, The roof of this dormer is a flat plane approximately horizontal. Shed dormer, This dormer also has a flat plane roof. A shed dormer can provide head room over an area than a gabled dormer. Wall dormer, As opposed to the dormer being set part way up the slope of the roof and this means that the face of the dormer is essentially a continuation of the wall above the level of the eaves. Eyebrow or eyelid dormer, A low and wide dormer with a curved roof, instead the roof covering is gradually curved up and over the dormer in a flattened bell curve. Link dormer, This can be a dormer that houses a chimney or a dormer that joins one part of a roof to another, bonneted dormer, This is an arched roof dormer, rounded in shape when viewed from front. Popular in Victorian homes, especially in areas, like the Southcott-style row-houses called Jellybean Row in St. Johns. Nantucket dormer, This is a three-in-one dormer structure composed of two gable dormers connected by a dormer in between. Lucarne, A dormer on the slope of a spire, usually slender. Blind or false dormer, A dormer that is visible externally. These are often used to make the house appear more aesthetically impressive, the word dormer is derived from the Middle French dormeor, meaning sleeping room, as dormer windows often provided light and space to attic-level bedrooms
9.
Cruck
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A cruck or crook frame is a curved timber, one of a pair, which supports the roof of a building, used particularly in England. This type of timber framing consists of long, generally naturally curved, timber members that lean inwards and these posts are then generally secured by a horizontal beam which then forms an A shape. Several of these crooks are constructed on the ground and then lifted into position and they are then joined together by either solid walls or cross beams which aid in preventing racking. The term crook or cruck comes from Middle English crok, from Old Norse krāka and this is also the origin of the word crooked, meaning bent, twisted or deformed, and also the crook used by shepherds and symbolically by bishops. Crucks were chiefly in use in the period for structures such as large tithe barns. However, these bent timbers were comparatively rare, as they were also in demand for the ship building industry. Where naturally curved timbers were convenient and available, carpenters continued to use them at later dates. For instance, base crucks are found in the roofs of the range of Staple Inn Buildings, Nos.337 –338, High Holborn. This is dated by documented records to 1586, with significant alterations in 1886 and further restorations in 1936, despite these changes, an authority on English Historic Carpentry, Cecil Hewett, has stated that these 16th-century crucks are original. There are also some fine, historically authentic reconstructions, for instance, Tithe Barn, Pilton, Glastonbury, whose original roof was destroyed by lightning, has been carefully rebuilt in 2005 from curved oaks. The necessary trees were sought out, using templates, in English woodlands. The large main barn of the manor house Barlow Woodseats Hall features what is claimed to be the longest continuously roofed cruck barn in Derbyshire, and possibly even in the United Kingdom. No cruck frames are known to have built in America though there are rare examples of what may be an upper cruck or knee rafters. Rare examples of framing are found on continental Europe such as in Belgium, Flanders, Northern France. An example of a Yorkshire cruck barn complete with a thatched roof can be found in Appletreewick. The crucks or cruck blades are an oak tree riven in two to form an equally shaped A frame. True cruck or full cruck, The blades, straight or curved, a full cruck does not need a tie beam and may be called a full cruck -open or with a tie beam a full cruck - closed. Base cruck, The tops of the blades are truncated by the first transverse member such as by a tie beam, raised cruck, The blades land on masonry wall and extend to ridge
10.
Pine
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A pine is any conifer in the genus Pinus, /ˈpiːnuːs/, of the family Pinaceae. Pinus is the genus in the subfamily Pinoideae. The Plant List compiled by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accepts 126 species names of pines as current, together with 35 unresolved species, the modern English name pine derives from Latin pinus, which some have traced to the Indo-European base *pīt- ‘resin’. Before the 19th century, pines were often referred to as firs, the genus is divided into three subgenera, which can be distinguished by cone, seed, and leaf characters, Pinus subg. Pinus, the yellow, or hard pine group, generally harder wood. Ducampopinus, the foxtail or pinyon group Pinus subg, strobus, the white, or soft pine group, generally with softer wood and five needles per fascicle Most regions of the Northern Hemisphere host some native species of pines. One species crosses the equator in Sumatra to 2°S, in North America, various species occur in regions at latitudes from as far north as 66°N to as far south as 12°N. Various species have been introduced to temperate and subtropical regions of both hemispheres, where they are grown as timber or cultivated as ornamental plants in parks, a number of such introduced species have become invasive and threaten native ecosystems. Pine trees are evergreen, coniferous trees growing 3–80 m tall. The smallest are Siberian dwarf pine and Potosi pinyon, and the tallest is a 81.79 m tall ponderosa pine located in southern Oregons Rogue River-Siskiyou National Forest, the bark of most pines is thick and scaly, but some species have thin, flaky bark. The branches are produced in regular pseudo whorls, actually a very tight spiral, the spiral growth of branches, needles, and cone scales are arranged in Fibonacci number ratios. The new spring shoots are sometimes called candles, they are covered in brown or whitish bud scales and point upward at first, then turn green. These candles offer foresters a means to evaluate fertility of the soil, pines are long-lived, and typically reach ages of 100–1,000 years, some even more. The longest-lived is the Great Basin bristlecone pine, Pinus longaeva, one individual of this species, dubbed Methuselah, is one of the worlds oldest living organisms at around 4,600 years old. This tree can be found in the White Mountains of California, an older tree, now cut down, was dated at 4,900 years old. It was discovered in a grove beneath Wheeler Peak and it is now known as Prometheus after the Greek immortal, pines have four types of leaf, Seed leaves on seedlings, born in a whorl of 4–24. Juvenile leaves, which follow immediately on seedlings and young plants, 2–6 cm long, single, green or often blue-green and these are produced for six months to five years, rarely longer. Scale leaves, similar to bud scales, small, brown and non-photosynthetic, needles, the adult leaves, are green and bundled in clusters called fascicles
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