In architecture or structural engineering , a girt , also known as a sheeting rail , is a horizontal structural member in a framed wall . Girts provide lateral support to the wall panel, primarily to resist wind loads .
15-415: A comparable element in roof construction is a purlin . The girt is commonly used as a stabilizing element to the primary structure (e.g. column, post). Wall cladding fastened to the girt, or a discrete bracing system which includes the girt, can provide shear resistance, in the plane of the wall, along the length of the primary member. Since the girts are normally fastened to, or near, the exterior flange of
30-859: A "major-rafter minor-purlin system". Common purlins are typically "trenched through" the top sides (backs) of principal rafters and carry vertical roof sheathing (the key to identifying this type of roof system). Common purlin roofs in North America are found in areas settled by the English and may have been a new invention in the Massachusetts Bay Colony. 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,
45-448: A column, stability braces may be installed at a girt to resist rotation of the unsupported, inner flange of the primary member. The girt system must be competent and adequately stiff to provide the required stabilizing resistance in addition to its role as a wall panel support. Girts are stabilized by (sag) rods/angles/straps and by the wall cladding. Stabilizing rods are discrete brace members to prevent rotation of an unsupported flange of
60-416: Is a roofing method of using boards as the weather barrier on a roof. Board roofs can be applied in several ways, the basic types have the boards installed vertically and installed horizontally. Double board roofs were sometimes used on railroad cars. Vertical board roofs may have the boards installed in a number of ways. The board-on-board roof has two layers of vertical boards, the upper layer covering
75-605: Is known as a "double roof" (a roof framed with a layer of principal rafters and a layer of common rafters). Principal purlins are further classified by how they connect to the principal rafters: "through purlins" pass over the top; "butt purlins" tenon into the sides of the principal rafters; and "clasped purlins," of which only one historic U.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
90-407: The boards themselves naga-itabuki (長板葺). The framing for a vertically boarded roof needs purlins spaced evenly apart instead of rafters . In parts on New England a common type of roof framing has common purlins which are boarded vertically, but evidence of these roofs having exposed boards as roofing is rare. Animal shelters may have board roofs which are a single layer with small gaps between
105-574: The building, lapped at the supports to develop a structurally efficient continuous beam across multiple supports. Note: The sketches in this section reference terminology commonly used in the UK and Australia. [REDACTED] This article incorporates text from a publication now in the public domain : Chisholm, Hugh , ed. (1911). " Purlin ". Encyclopædia Britannica . Vol. 22 (11th ed.). Cambridge University Press. p. 665. Board roof A board roof or boarded roof
120-596: The complexities of this interactive design condition to ensure competent design of the complete structure. This architecture -related article is a stub . You can help Misplaced Pages by expanding it . Purlin A purlin (or historically purline , purloyne , purling , perling ) is a longitudinal, horizontal, structural member in a roof . In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin, and common purlin. Purlins also appear in steel frame construction. Steel purlins may be painted or greased for protection from
135-532: The environment. 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, though the accuracy of this claim has been disputed. A purlin plate in wood construction is also called an "arcade plate" in European English, "under purlin", and "principal purlin". The term plate means a major, horizontal, supporting timber. Purlin plates are beams which support
150-556: The gap between the boards in the lower layer. The lower layer may be spaced apart or installed tightly together. In any type of vertical board roof the boards may be grooved to catch runoff. The board-and-batten roof the upper layer are slender pieces of lumber called battens . The lower layer of boards are installed tightly because the battens are narrow. Traditional roof coverings in Japan are mostly thatch, tile and wood shingle but some board roofs were used and are called yamatobuki (大和葺),
165-437: The girt. Sheet metal wall panels are usually considered providing lateral bracing to the connected, typically exterior flange along the length of the girt. Under restricted circumstances, sheet metal wall panels are also capable of providing rotational restraint to the girt section. In general: Girt supports panel, panel stabilizes girt; Column supports girt, girt stabilizes column. The building designer should be knowledgeable in
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#1733125026514180-665: The highest concentration in Maine, and isolated parts of New York and along the St. Lawrence River in Canada. One of the oldest surviving examples is in the Coffin House in Newbury, Massachusetts, from 1678. The purpose of a common purlin roof may be they allow a board roof , that is a roof of nothing but vertically laid boards with seams covered with battens or another layer of boards. In steel construction,
195-490: The letter Z are referenced as Z shapes. Section designations can be regional and even specific to a manufacturer. In steel building construction , secondary members such as purlins (roof) and girts (wall) are frequently cold-formed steel C, Z or U sections, (or mill rolled) 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
210-527: 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 timber-framed building. Principal purlins in wood construction, also called "major purlins" and "side purlins," are supported by principal rafters and support common rafters in what
225-791: The term purlin typically refers to roof framing members that span parallel to the building eave, and support the roof decking or sheeting . The purlins are in turn supported by rafters or walls. Purlins are most commonly used in Steel Framed Building Systems, where Z-shapes are utilized in a manner that allows flexural continuity between spans. Steel industry practice assigns structural shapes representative designations for convenient shorthand description on drawings and documentation: Channel sections, with or without flange stiffeners, are usually referenced as C shapes; Channel sections without flange stiffeners are also referenced as U shapes; Point symmetric sections that are shaped similar to
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