Building Construction Definitions

• Shed roof

- a pitched roof that slopes in one direction only from the ridge

• Truss

- a wooden or structural unit made up one or more triangles in a flat plane. Because of the inherent strength of the triangles within its structure, when truss is intact it is much stronger than the individual members it is made of

5 types of construction

1)fire resistive 2)non cumbustible 3)ordinary 4)heavy timber 5)wood frame

• Butterfly roof

a V shaped roof in which two sides slope toward a valley in the middle. An unusual type roof that is rarely seen in cold climates where snow load is a factor

• Cantilever

a beam that is unsupported at one or both ends. Typically used to support balconies on apartments or some office buildings

• Compression

a force that tends to push the mass of a material together. Bearing walls in a building are under compression from the weight of the roof and other materials above.

• Beam

a horizontal structural component subjected to vertical loads. Typical beams are steel or wooden I beams or large dimension wooden members

• Girder

a horizontal structural member used to support beams or joists. Almost always of larger dimensions than the members they support

• Bar joist

a joist constructed of steel with bars in the vertical web space. A common structural component in office buildings and other commercial structures, very high strength to weight ratio except when exposed to the heat of a fire- failure likely

• Open web joist

a joist constructed with a web composed of materials such as bars or tubes that do not fill the entire web space. These are very common building assemblies because their strength compared to their cost. When exposed to fire they lose strength quickly

• Mortar

a mixture of sand, cement, water used to bond masonry units into a solid mass. The joists between bricks are filled with mortar. Mortar joints are sometimes the easiest to penetrate when a masonry wall must be breached.

• Gable roof

a pitched roof characterized by square cut ends and sides that slope down from the ridge line to the eaves. These are the most common roof style on homes or small buildings

• Hip roof

a pitched roof in which the ends are all beveled so that there are no gable walls. A common roof style on many newer residences. Unlike gable roofs, in hip roofs the attic vents are only under the eaves or on the roof

• Fire door

a rated assembly consisting of a solid core door, door frame, and hardware. Fire doors are used to confine a fire to one room or section of a building by closing a communicating opening when triggered by a fire. If fire doors are to function as designed, they must not be prevented from closing by being intentionally or inadvertently blocked

• Fire wall

a rated assembly that extends from the foundation to and through the roof of a building to limit fire spread. Fire walls are intended to confine a fire to one room or section. If they are penetrated by openings not protected with fire doors, fire can spread

• Bowstring truss

a roof assembly with a curved arched top chord and a horizontal bottom chord. These assemblies are very strong except when exposed to direct flame contact when catastrophic failure without warning may occur

• Gambrel roof

a roof characterized by a single ridge line from which roof sections on both sides of the roof descend at two different pitches. These roofs are common on barns and other farm structures. Difficult to use roof ladders on

• Mansard roof

a roof characterized by steeply sloped facets surrounding a flat or nearly flat center section. Many remodeled buildings have false mansard roofs that consist of a fascia added to an existing flat roof. Some cases fascia forms a concealed space where fire can burn undetected.

• Flat roof

a roof that is flat or nearly flat relative to the horizon. Many commercial buildings have flat roofs covered with tar or gravel or other weather proof material. Flat roofs lend themselves to being opened for vertical ventilation

• Pitched roof

a roof that is sloped to facilitate run off. Pitched roofs range from those that are flat to those that are extremely steep. Churches

• Saw tooth roof

a roof with a profile of vertical and sloping surfaces that resemble a saw blade. These roofs are common on older industrial buildings. The vertical walls of these roofs usually include many windows. Natural ventilation.

• Parallel chord truss

a truss constructed with the top and bottom chords parallel. These trusses are used as floor joists in multistory buildings and as ceiling joists in buildings with flat roofs

• Balloon frame

a type of wood frame construction in which the studs in exterior walls extend from the basement or foundation to the roof. This type of construction allows fires to spread -often undetected from basement to the attic through hallow walls

• Stud

a vertical structural member in a frame wall. Stud walls are assemblies to which wall coverings are nailed or screwed. Wood or light gauge steel

• Column

a vertical supporting member. Columns may be wooden or steel posts, steel posts often support lightweight roof assemblies, and if unprotected by surface insulation, steel posts may fail quickly in a fire.

• Parapet

a wall at the edge of some roofs. Most parapet walls range from a few inches to a few feet. Trip hazard

• Gable wall

a wall rising to meet a gable roof at the end of a building. These walls are found only at the ends of gable roofs and they often include an attic vent near the top of the wall

• Party wall

a 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 a party wall can affect the structural integrity of the adjoining building

• Glue lam beam

a wooden structural member composed of relatively short pieces of lumber glued and laminated together under pressure to form a long, extremely strong beam. Because of the mass of most glue lam beams, they resist fire extremely well compared to other materials

• OSB Oriented strand board

a wooden structural panel formed by gluing and compressing wood strands together under pressure. This material has replaced plywood and planking in the majority of construction. Roof decks, walls, subfloors are all made of OSB

• Plywood

a wooden structural panel formed by gluing and laminating very thin sheets of wood together under pressure. Plywood is still used in some applications but has been replaced in construction by OSB

• Interstitial space

an accessible or inaccessible space between layers of building materials; an attic or cockloft sometimes used to house HVAC and other machinery. Like attics or cocklofts, unless protected they can spread fire to burn

• Lamella arch

an arch of constructed of short wooden members connected in a specific geometric pattern. While rare in modern construction, these roof assembles can still be found in old buildings

• Attic

an open space between the roof and ceiling of a building; most commonly found in single - and multifamily residential occupancies. Attics provide open spaces in which fires can burn undetected or spread throughout a structure

• Cock loft

an open space between the roof and ceiling of a commercial or industrial building. Usually found under flat or nearly flat roof. In a fire these spaces act the same as an attic

• Rafters

beams that span from a ridge board to an exterior wall plate to support roof decking, while it is important to cut away roof decking during vertical ventilation, cutting rafters can weaken a roof and should be avoided

• Header course

course of bricks laid with the ends facing outward. Because the ends of the bricks are smaller than the sides, a header course is easy to identify. Header courses are only used in unreinforced masonry, and this makes that type of construction easy to identify

• Spalling

degradation of concrete due to prolonged exposure to high heat, water trapped

• Tension

force that tends to pull the mass of a material apart, tension is what causes some roof assembles to pull away from walls and fall inward

• Platform construction

frame type construction in which each floor interrupts the exterior studs forming an effective fire stop at every floor. This is most common type of construction used to frame modern residences and other small buildings

• Drywall

gypsum wall board. A fire resistive wall covering also called sheet rock

• HVAC

heating, ventilating, air conditioning. Can allow smoke and fire to spread throughout

• Course

horizontal layer of masonry units. A row of bricks is an example of a course

• Joists

horizontal structural members used to support a ceiling or floor. Drywall materials are nailed or screwed to the ceiling joists, and the subfloor is nailed or screwed to the floor joists

• Gypsum board

interior finish material consisting of calcinated gypsum, starch, water, and other additives sandwiched between two sheets of specially treated paper

non load bearing

interior that supports own weight only

• Curtain board

no-load bearing interior wall extending down from a roof or ceiling to limit the horizontal spread of fire and heat. If curtain walls are penetrated by unprotected openings, fire can spread

• Curtain wall

non load bearing exterior wall used as a weather barrier but not for structural support. On many high rise buildings, the outside walls are curtain walls

• Chip board

oriented strand board

• Decking

planks or panels of plywood or oriented strand board (OSB) that form the substrate of a roof assembly. In vertical ventilation through a roof decking must be removed from the ventilation opening to realize the full effect of the opening

• Sheathing

plywood, OSB, or wooden planking applied to a wall or roof over which a weather resistant covering is applied, most sheathing is relatively easy to penetrate for forcible entry or ventilation

• Reinforced concrete

poured into forms that contain an interconnected network of steel rebar

• Rebar

reinforcing bar. Steel bars are placed in concrete forms before the cement is poured. When the concrete sets the rebar within it adds strength

partition wall

separate a large space into smaller spaces

load bearing wall

structural support

• Eave

the edge of a pitched roof that overhangs the outside wall. Attic vents in typical eaves provide an avenue for an exterior fire to enter the attic

• Chord

the main structural members of a truss as distinguished from diagonals chords span the open space between the upper and lower diagonal members in a truss assembly.

Fire load

the maximum heat that can be produced if all combustible material in an area burn

• Pitch

the ratio of rise to span of a roof assembly. The steeper the pitch, the greater the slip hazard unless roof ladders are used

• Plate

the top or bottom horizontal member of a frame wall. The sole plate is nailed or screwed to the subfloor and the top plate is what the roof assembly rests on

• Fire load

total potential heat release if a building and its contents burned. The fire load of a fully stocked lumber yard is higher than that of an empty building

• Rated assembly

two or more construction components combined to form an assembly that has a specific fire resistive rating. A fire door is an example of a rated assembly

• Assembly

two or more interconnected structural components combined to meet a specific function or design requirement. Typical assemblies are roof trusses, wall frames, and doors including frames

veneer walls

walls with an attractive surface laid over base

• Engineered I beam

wood I beam consisting of continuous wooden upper and lower chords separated by a web of OSB or similar sheet stock

• Gusset plate

wood or metal plate used to connect structural members that are butted together; most often used in the construction of trusses. Many metal gusset plates are simply pressed into the wood and are subject to early failure if the plates warp from the heat of the fire. Nailed or screwed together are much more reliable.