Lesson 5

pdf

School

Seneca College *

*We aren’t endorsed by this school

Course

OHS104

Subject

Civil Engineering

Date

Oct 30, 2023

Type

pdf

Pages

Uploaded by ChancellorAlpaca3744

Lesson 5: Building Design Affecting Fire Protecting Building and site planning for fire safety The conception, design and construction of a new home, the renovation of the home or the design of a new building can be a very exiting, sometimes challenging and hopefully always rewarding venture. In the conception of a new building, we should always consider certain key elements in the planning stage. Some of these elements may seem basic, others not so much. Although we can determine usage for the building and what we want it to look like, as we saw in the previous lesson, the Building Code will provide the minimum parameters for how the building is to be put together and what must be found in it. Having said all this, there is usually latitude with respect to the Building Code regarding some of the fire and life safety systems. In some instances the Building Code requires sprinkler systems, but in situations where it might not, it might still be advantageous to put such a system in during the design and construction phase. Although we will be looking at sprinkler systems in greater detail in another lesson, the reason for considering them, even in the residential setting is that they have proven themselves time and time again in significantly reducing damage and preventing fire related death. Their small extra cost in the construction phase is usually offset by the reduction in insurance premiums. Considerations in building and site planning can involve traffic and transportation patterns, fire department access, and firefighting water supplies. Traffic and transportation patterns: We need to decide on the land, and where the building we are considering is to be located as well as its footprint. We also need to look at how close to the roadway to place it, is there a major arterial road, are there secondary access roads, how long would it take for the fire department to reach us if we sit in a large field with only one access road available to us? These are all serious considerations as increased response times for the fire department may mean increased property damage. Fire department access: Fire department access is the next consideration. Can fire personnel access all sides of the building? Are there overhead wires, trees or building design features that could impede the raising of fire service ladders or aerial platforms? Are the access roads wide enough for full extension of the outriggers on the aerial platforms? Is the road bed strong enough to support the fire service vehicles and those vehicles with outriggers? If the answer to these questions is no, then serious consideration must be given to trying to control the potential fire from within. Firefighting water supplies:

As we will see in a later lesson, water is still the most effective suppression agent. When applied in the right amounts it can cool the fuel to below the temperature where pyrolysis occurs. The key is to ensure that there is adequate water supply for firefighting operations. Many cities provide water for firefighting operations by means of underground pipes and above ground hydrants which are essentially water valves. Although we will discuss hydrants further in a later lesson, it is important to understand that even with this system there may be insufficient water supply to fight a major fire. Some building owners have resolved the water supply issue by providing a holding tank with a set amount of water, that remains full at all times to provide water for the sprinkler systems and standpipe/hose systems. In rural areas, where hydrants and piped water supplies are impractical, it is not uncommon to see the rural fire services draw water from swimming pools, streams, lakes, ponds, etc. The vehicles in the rural fire service also tend to have larger water tanks than city fire services for much this reason as well. Objectives of fire-safe building design In terms of building design it is important to understand the needs of the user and balance those needs against the activities that will be undertaken in the building. The whole point is to try and keep one of the three components of the fire triangle out of the picture. In looking at heat, oxygen and fuel, the only one that can be reasonably controlled is heat. More specifically we need to try and eliminate ignition sources. Realistically however, this can be quite challenging as these ignition sources could be the heating equipment, cooking equipment, open flames from welding or hot work, sometimes arson, sometimes lightning, sometimes carelessly discarded smoking materials. We need to consider f our aspects in terms of safe building design . They are: Life safety Property protection Continuity of operations Environmental protection Life safety: In terms of life safety, some of the most effective actions we can take in the building design are to have a good detection and warning system, a good suppression (sprinkler) system with effective coverage throughout the building, clear and clearly labelled emergency exits from the building and clear instructions and training of all occupants of that building. Property protection: Property protection refers to the suppression systems to minimize the amount of fire damage. It also refers to the compartmentalization to minimize smoke and flame spread in the building. It also refers to constructing the building of fire resistive materials. An interesting point here is that very often the building

finishes are fire resistant and yet the end users place combustible materials on the walls (i.e. posters) which defeat the purpose of the fire resistive materials. There are other strategies, such as effective compartmentalization, which would also work. Continuity of operations : Continuity of operations refers to how quickly an organization, company or other is back on their feet after a fire. One area which clearly highlights this is the database for human resources/payroll. Large organizations usually have the key information on a server which is then backed-up on a set basis, possibly daily, and the back-up stored in a remote location. In this way, should a fire occur, key corporate records are not lost. Again, as in the previous one on Property Protection, sprinkler systems, whether water or some type of chemical agent, will go a long way to protect what is valuable to a corporation or company by minimizing the amount of damage. Environmental protection: Depending on the type of facility, fire protection may not be the answer or it may be that normal fire department suppression activities should not be used due to the serious concern of environmental damage that may be caused by the fire department’s activities. In one case in the past, where a chemical manufacturer’s production plant caught fire, the water run-off from fire suppression activities mixed with numerous toxic chemicals in the plant, requiring a significant environmental clean-up. When a similar fire occurred in a similar production facility the fire department this time chose to let it burn and protect the exposures or adjacent buildings, significantly reducing the pollution caused by the fire. “Environmental protection can be enhanced with the installation of automatic fire-extinguishing systems that limit the fire size and minimize the subsequent fire-fighting waer runoff.” [Cote, Fundamentals of Fire Protection] Some key construction terms There are certain terms that we use in building construction, fire inspection and investigation referring to building structures. Terms used are combustible and non-combustible material, limited combustible material, fire barrier wall, fire resistance rating, fire wall, flame spread rating, flame resistance and flame retardant. Each has a special meaning. The NFPA defines them as follows: Combustible (material): A material that, in the form in which it is used and under the conditions anticipated, will ignite and burn; a material that does not meet the definition of non-combustible, or limited combustible.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Noncombustible (material): Refers to a material that, in the form in which it is used and under the conditions anticipated, does not ignite, burn, support combustion, or release flammable vapors, when subjected to fire or heat. Limited combustible material : Refers to a building construction material not complying with the definition of non-combustible that, in the form in which it is used, has a potential heat value not exceeding… Fire barrier wall : A wall, other than a fire wall, having a fire resistance rating. Fire barrier walls are used to protect buildings from areas of increased hazard or risk or to provide protection for purposes of egress. Fire wall : A wall separating buildings or subdividing a building to prevent the spread of fire and having a fire resistance rating and structural stability. Flame spread rating : A relative measure of the surface burning characteristics of building materials. Flame resistance : The property of a material whereby combustion is prevented, terminated, or inhibited following the application of a flaming or nonflaming source of ignition, with or without the subsequent removal of the ignition source. Flame resistance can be an inherent property of a material, or it can be imparted by specific treatment. Flame retardant : So constructed or treated that it will not support flame. Types of building construction There are 2 basic types of construction. They are non-combustible and combustible. Both types are further sub-divided. 1) Non-combustible construction has 2 types, Type I and Type II. Type I construction is also known as fire resistive construction. This is the highest fire resistive construction, typically with 2 to 4 hour fire rating depending on the structural member, whether a roof support, a load bearing wall support or some other. Type I construction is further sub-divided but for our course purposes we don’t need to go into that level of detail. Type II construction is one where the structural elements are of materials that are non-combustible or of limited combustibility. There are 3 subdivisions to this type. 2 of them require some level of fire resistance, usually 1 or 2 hours, and the 3rd, is of non-combustible or limited combustible structural elements. 2) Combustible construction has 3 types, Type III, Type IV and Type V. Type III construction has 2 hour fire rated exterior walls that are non-combustible or have limited combustibility. All other components are combustible, usually being made of wood. The characteristic of this type of construction is that the building appears to be non-combustible on the exterior, with either a block or brick wall but all other structural elements are wood.

Type IV construction involves the use of heavy timbers. All structural timbers must be of a specific minimum size to allow the structure to qualify as a type IV. As an example, columns for supporting floors must be 8” x 8” and columns for supporting roofs must be 6” x 8”. These are nominal sizes, meaning that the wood cannot be any smaller than these values. By way of illustration, a standard 2” x 4” which is readily available at the lumber yards in Canada is actually 1 ½” x 3 ½”. This is what is referred to as the nominal or actual size of the wood. We will see shortly just how important this is. Activity – Can you think of any structures that are of this type (type IV)? Go to the discussion/forum 5b and post your answer. Type V construction is the most commonly used type. It is found in houses, small buildings, garages, and many other types of structures. This type of construction uses either 2” x 4” or 2” x 6” wooden studs for the walls. Roof trusses are often used as well, being made of 2” x 4” studs. Although this type of construction is very popular, it is also the one which will likely burn the most rapidly with fairly rapid structural collapse as the 2 x 4 as we saw before is not the actual stud size which means far less wood. The exposed wood being small in size will burn fairly quickly. Where there is a mixture of construction types, it is recommended to classify according to the lower construction type. By way of example, it is common to see concrete parking structures (Type I) under low rise apartment buildings of ordinary wood construction (Type V). The classification would be Type V. Another important point is that in most jurisdictions a lower type construction cannot support a higher type construction due to the lesser fire resistance of the lower type. That is to say that you could not, by way of example, place a concrete building on top of a wooden structure. Building materials A walk through different types of buildings and in most home renovation stores show us that there are numerous types of building materials readily available. We will quickly review some of the more common types and some of their advantages and disadvantages. Wood: It is one of the most common types of building materials. It is easy to use and has been used for all manner of building function, from structure to interior finish, to interior furnishing. It is also found in the form of plywood and particle board. The primary disadvantage of wood is that it burns. The smaller the size of the wood, the faster it will burn. Steel: It is also a commonly used building material. It is used to form the skeleton or frame of many structures. It is also used for the exterior walls. Some of the disadvantages are that it is difficult to work, requiring a cutting torch or saw, difficult to fasten, requiring bolts, or welding and hard to handle due to its weight. It does have the advantage of being non-combustible. However, if exposed to heat, it will expand (stretch)

losing its tensile strength. An additional problem is that it conducts heat so that if it is hot and in contact with combustible materials, a fire may break out. Most steel used in construction is required to have protection, by means of some sort of fire resistive coating such as asbestos (no longer used) or some other material. Concrete is sometimes used to encase steel due to its tolerance for heat. Concrete and masonry: Concrete is a mixture of water, aggregate and cement. It tends to have very good fire resistive properties because of its components, as it is able to absorb large amounts of heat because of the water and aggregate. Concrete is also reinforced, depending on its application by means of reinforcing rods also known as re-bar or some other means. This provides tensile strength to the concrete. Glass: It is commonly used as glazing for windows and doors. Glass is not very fire resistive. The disadvantage is that it breaks when exposed to heat as the tensile strength is not very high. Reinforcing the glass with wire mess improves the fire resistance. The advantage of glass is that it makes an effective smoke barrier. Plastics and Composites: Widespread use of plastics is not common in building construction. One of the main reasons is the amount and type of toxic smoke that they would give off as they melt in a fire situation. They also tend to melt and burn at much lower temperatures than ordinary building materials. Plastic is found on a limited basis in the home as trim, insulation, interior finishings and plumbing. Fiberglass reinforced plastic is also found in shingles, bath fixtures, siding materials and other places around the home. The fibreglass is not combustible, however the resin used is. Gypsum and plaster : Plaster used to be a very common interior finishing material until the advent of gypsum board or drywall. The advantage of the gypsum board and drywall is its fire resistance and it is used to protect structural wood and steel. The disadvantage is that it damages easily. Other common materials: Other materials used are brick and tile. Brick is used to construct walls whereas tile is commonly used as a wall finish (kitchen or bathroom) and as a floor finish. Fireplaces in the home are a good example of the use of both materials, where the brick is found around the fireplace on the wall and the tile forms part of the hearth. Both materials tend to have relatively good fire resistive properties. Another point is that “because of the prevalence of brick construction in European dwellings as compared with American wood-frame construction, the dwelling fire record in Europe is much more favorable than the dwelling fire record in

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version