In building construction and in fire prevention there are organizations that have created a useful system on how to determine what type of building falls under which category. The ICC (International Code Council) and the NFPA (National Fire Protection Association) create these building codes for the safety of firefighters. The two most commonly known standards for building classifications are the NFPA 5000 and also the International Building Code (IBC). The two are very similar, however, they different on sub-categorizing.
The International Building Code uses Roman numerals behind the type of construction. In addition to subcategories with letters for each five classes and the amount of fire resistance provided for each building. NFPA uses Roman numerals behind the type of construction. Unlike the IBC, NFPA uses a 3-digit number system behind that to sub categorize the fire hourly rating for the load-bearing walls, for the beams and columns, and for the floor construction. The IBC and NFPA breaks down construction in to five classes, Type I, Type II, Type III, Type IV, and Type V.
Type V buildings are known as wood frame construction. To break Type V constructions to the basics, they are constructed of lightweight materials to save the contractor money. This type of construction is the most dangerous to firefighter due to the lightweight, cost effective materials used. Some of the wood frame buildings are Log cabins, Post and frame, Balloon Frame, platform frame, plank and beam, and truss frame. Log cabins are structures that are built out of tree logs. The ends are notched in order for the logs to be stacked on top of each other.
Just like the popular toy, Lincoln Logs, these buildings are built the same way. The interior walls are usually wooden boards with a lacquer finish or a gypsum board finish. Due the types of interior finishing, it can help a going or started fire indoors spread within seconds. The lacquer finishing proposes an extreme fire hazard for both firefighters and the occupants. Post and Frame construction types of structures came to America from Europe. This type of construction was fitted together using a wooden frame and timber. They connected at joints called mortise and tenon.
To ensure that load transfer was properly distributed they used wooden pins to hold the connected piece together called trunnels. Like log cabins, the interior wall finishing’s we often made of wood. This poses a danger to firefighters as well because it just adds more fuel to a structure fire. Balloon Frame construction derived from Post and Frame types of construction. The two types of construction are very similar in many ways. The differences between the two are that Balloon Frames didn’t require a skilled laborer to cut the notches in the timber and studs.
Instead, by using nails it would hold the frame together. The studs would be nailed on to horizontal board called a ribbon. This type of construction introduced a hazard to firefighters due to the void space in the walls. Unlike modern day construction, these construction types didn’t have horizontal piece in between studs called fire stops. So if a fire was to start from a basement of a Balloon Frame structure, the fire itself would travel along the void spaces in the walls and into the attic area of the home.
Platform Frame construction was an improved version of Balloon Framing. Platform Framing was constructed one floor at a time, which allowed confining a fire in between walls from level to level. How this work was basically they would build the first floor with the second story joist attached. When those walls are erected then the second story sub floor is built. Platform Framing and Balloon Framing shared similar characteristics such as open stairwells and soffits. Soffits are void spaces above built in cabinets usually in kitchens.
These two types of construction methods also shared similar characteristics on using either plywood or OSB board (oriented strand board) for the sub-flooring, which are laid on top of the joist. Plank and Beam construction was a more cost effective way for contractors, architects, and interior designers to develop a structure. This type of construction took heavier beams and spaced them further apart. In addition, it didn’t use plywood or OSB board for sub-flooring. Instead it used thick tongue and grooved planks.
This type of construction created a lot of open headspace in the kitchen, living rooms, dining rooms, and family rooms. This was an improvement in construction types for firefighters because interior fires can be easily contained. However, because of interior finishes, flame spread would be a serious problem. This structure design also poses another fire hazard which claims firefighter lives every years, which is roof collapsing. Truss Frame construction is known to be the most common and most often used type of construction today because it is cost effective.
This construction type was first thought to be safe and durable, but under fire condition it poses a different kind of factor. Truss frame construction is made of lightweight woods that create triangles for support. Inside of the main triangle or parallel chords are links called Webbings that provided extra support. These triangles, parallel chords, and links are all held together but metal plates called gusset plates. This type of construction is a serious problem to fire fighters because of all the materials used.
The lightweight wood material is easily ignited during fires and the metal gusset plates are nothing more then flat metal plates with spikes on one side that is stamped into the wood. The gusset plates hold the parallel chords and triangles together, but in fire conditions, these gusset plates are heated up and tend to “clam shell” then fall off. When this happens, truss failure usually happens and in results to a roof collapse. Type IV buildings are also known as Heavy Timber or Mill construction. Heavy Timber construction is what derived out of Mill construction.
Some of the features of a Type IV building would be: heavy timber for columns and beams, 3 inch thick laminated wooden flooring and planks, fire cuts on girders, cast iron boxes on the walls holding the end of the girders, and exterior bearing and nonbearing walls are usually stone, brick or masonry. When these buildings were first built they were used as factories and textile mills. As years go on different companies and factories occupy the space, which can oppose a different kind of hazard, when an interior fire breaks out.
This can be a problem because oil residuals and other chemicals spilled by different occupants can increase the fires intensity. When heavy timber type buildings get induced in fire, they portray a hazard for firefighters and the community around them. The amount of radiant heat that is given off can be felt hundreds of feet away, which can lead to a secondary structure fire near by. Due to the types of materials in a Type IV building, the timbers itself can burn for many hours and create lots of fire embers that can be carried hundreds of feet away to near by housing units. Now at days and becoming more popular, vacant type 4 buildings are being renovated and used as apartment style living areas.
Even though these buildings are becoming more popular for other uses, not many of them are being built because of the cost of heavy timber. In order for these buildings to be fitted for housing occupants, they will have to be retro fitted with sprinkler systems, and meet the NFPA standards for housing. Type III construction is also known as Ordinary construction. This type of building is seen all over America in cities that have a historical area (main street USA) used as strip malls.
The typical Type III construction is made of brick, rock, or masonry bearing walls and non bearing walls with wooden joists used as simple beams spanning from wall to wall parallel to the store front. At times depending on the contractor the walls may use one type of material then there are times two types of materials are used. If two types of materials are used it would usually be brick and concrete blocks which is called composite construction The roof is similar to floor construction from floor to floor, or it can have a peak created by trusses.
If there were a peak, there would most likely be a cockloft, which is a void space between the top floor ceiling and the roof. Type II construction is also called Non Combustible construction. This type of construction is very similar to Type I construction. Even though that concrete is used in Type II construction, the very core of Type II construction would be the use of steel I-beams and H-beams. Type II construction relies on the steel in every aspect from the framing of the walls to the roof and floor supports. Even though that Type II construction is Non Combustible, they do portray a threat to firefighters.
The reason is because steel conducts heat very well and would fail at 1000 degrees Fahrenheit. At 1000 degrees Fahrenheit, steel at 100 feet would gain and extra 8 to10 inches in length. This would cause wall collapses. Type I construction is also called Fire-Resistive construction. This type of construction uses mainly concrete and steel. The outer walls are sometimes assembled together but lifting one concrete slab at a time. These types of builds inherited the name concrete tilt ups. In most part if steel were to
be used in a Type I structure, it would be to reinforce the concrete because concrete is strong in compressive strength but weak in tensil strength. If there is any exposed steel, it is fire proofed with a fire retardant. Mainly the fire hazards that firefighters have to face in these structures are usually because of human error during the construction of the buildings or when occupants are occupying the building. In a construction sites welding, cutting, plumber’s torches, electrical wiring, and heaters all pose a fire hazard. The other risk of this type of building would be of a collapse of the concrete walls or floors during construction.