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| Two or more interconnected structural components combined to meet a specific function or design requirement. Roof trusses, wall frames, and doors including their frames. |
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| Open space between roof and ceiling of a building; most commonly found in single and multi-family residences. Fire can burn undetected and throughout structure. |
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| Joist of steel with bars in the vertical web space. Common in office buildings. Fails early in heat. |
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| Wood-frame construction in which the studs in exterior walls extend from the basement or the foundation to the roof. Fire can spread undetected from basement to attic. |
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| Horizontal structure with vertical loads; can be steel or wood. |
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| Roof with a curved (arched) top chord. "Stadium" roof. Prone to catastrophic failure with direct flame contact. |
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| V-shaped roof with two sides sloping to a valley in the middle. Rarely seen where snow load is a factor. |
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| Beam unsupported at one or both ends. Typically used to support balconies on apartments and office buildings. |
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| Main structural members of a truss as distinguished from diagonals. Span the open space between the upper and lower diagonals. |
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| Open space between the roof and ceiling of a commercial or industrial building. Usually under flat roofs. In a fire, they act much like attics. |
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| Vertical supporting member. Made of wood or steel. If unprotected by insulation, it may fail quickly in a fire. |
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| Force that tends to push a mass together. |
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| Horizontal layer of masonry units. Ex: a row of bricks. |
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| Nonload-bearing interior wall extending from the ceiling to limit horizontal spread of fire and heat. |
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| Nonload-bearing exterior wall used as a weather barrier, but not structural support. On high-rise buildings, the outside sheet glass in frames are these. |
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| Planks of plywood or OSB that form the substrate of a roof assembly. In vertical ventilation, this must be removed. |
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| Gypsum wall board. Fire-resistant. |
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| Edge of a pitched roof that overhangs an outside wall. Attic vents through these provide an avenue for an exterior fire to enter the attic. |
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| Continuous wooden upper and lower chords separated by a web of OSB or sheet stock. |
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| Rated assembly of a door, door frame and hardware. Contains a fire to one room or section when triggered. Must not be prevented from closing. |
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| Total potential heat release if a building and its contents burned. (Ex: lumber yard > empty building) |
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| Rated assembly that extends from the foundation to and through the roof of a building to limit fire spread. If penetrated with openings not protected by fire doors (plumbling and electrical), the fire can spread unchecked. |
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| Common on commercial buildings; covered in tar or gravel. Easy for vertical ventilation. |
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| Pitched roof characterized by square-cut ends and sides that slope down from the ridge line to the eaves. Most common style on homes and small buildings. |
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| Wall rising to meet a gable roof at it's end. Often include an attic vent near the top. |
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| Roof characterized by a single ridge line which roof sections on both sides descend at different pitches. Common on barns and other farm structures. Roof ladders are difficult to use on them. |
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| Horizontal structure member used to support beams or joists. Almost always a larger dimension than the members they support. |
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| Short pieces of timber glued and laminated together under pressure to form a long, extremely strong wooden beam. Resist fire extremely well. |
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| Wooden or metal plate used to connect structural members, most often in the construction of trusses. Fails early, dangerous to firefighters unless nailed or screwed in. |
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| Bricks laid with ends facing outwards. Only used in unreinforced masonry. |
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| Pitched roof in which the ends are all beveled so that there are no gable walls. Common on new residences. Attic vents are only under the eaves or on the roof. |
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| Heating, Ventilation and Air Conditioning. Needs to be properly installed with automatic fire dampeners, or smoke and fire can spread throughout a building. |
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| Space between layers of building materials; much like attics and cocklofts. Sometimes used to house HVAC and other machinery. Unless properly protected, a fire can burn undetected and spread throughout a building. |
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| Horizontal structural members used to support a ceiling or floor. Drywall is nailed or screwed to these on the ceiling, and subfloor on the floor. |
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| Arch constructed of short wooden members in a specific geometric pattern. Rare in modern construction. |
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| Roof characterized by steeply sloped facets surrounding a flat section. Remodeled buildings can have false mansard roofs with a fascia over an existing flat roof. Fascia can form a concealed space in which a fire can burn undetected. |
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| Mixture of sand, cement and water used to bond masonry units. Easy to penetrate if a wall must be breached. |
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| Constructed with a web composed of materials such as bars or tubes that do not fill the entire web space. Very common because of their strength compared to their cost. Lose strength quickly in a fire. |
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| Oriented Strand Board (OSB) |
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| Wooden structural panel formed by gluing and compressing wood strands under pressure. Has replaced plywood and planking. Roof decks, walls and subfloors are commonly made of these. |
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| Constructed with the top and bottom chords parallel. Used as floor joists in a multistory building and celing joists in buildings with flat roofs. |
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| Decorative wall at the edge of a roof. Can be a significant trip hazard for firefighters on the roof. |
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| Wall shared by two adjoining buildings; usually a load-bearing wall that is also a fire wall. The failure of a roof assembly attached to this can affect the integrity of the adjoining building. |
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| Ratio of rise-to-span on a roof assembly. When this is greater, the greater the slip hazard unless roof ladders are used. |
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| Roof that is sloped. Can be extremely steep, such as on churches. |
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| Top or bottom horizontal member of a frame wall. Nailed or screwed into the subfloor or roof assembly. |
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| Each floor interrupts the exterior studs forming an effective fire-stop at every floor. Most common in modern residences and other small buildings. |
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| Wooden structural panel formed by gluing and laminated very thin sheets of wood under pressure. Still used, but replaced by OSB. |
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| Beams that span from the ridge board to an exterior wall plate to support the roof decking. Cutting these can seriously weaken a roof and should be avoided whenever possible. |
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| Has a specific fire-resistance rating. (Ex: Fire door, wood frame wall covered with gypsum drywall). |
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| Reinforcing bar. Steel bars placed in concrete before the cement is poured; adds considerable strength. |
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| Roof with vertical and sloping surfaces resembling a saw blade. Common in older industrial buildings. Includes many windows in walls which can be opened or removed for natural ventilation. |
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| Plywood, OSB or planking applied to a wall or roof over which a weather-resistant covering is applied. Easy to penetrate. |
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| Pitched roof that slopes only in one direction. |
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| Degradation of concrete to prolonged exposure in high heat. Water trapped within the concrete is vaporized by the heat and expands, and the concrete breaks apart. Sounds like gunfire, but relatively harmless. |
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| Vertical structural member in a frame wall. Can be made of either wood or light-gauge steel. |
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| Force that tends to pull the mass of a material apart. What causes some roof assemblies to pull away from walls and fall inwards. |
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| Wooden or metal unit made up of one or more triangles on a flat plane. Much stronger with triangles together than separate. |
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| Oriented Strand Board - OSB (pic) |
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