Chapter 3: Building Construction Flashcards
Building codes
regulate: the type of construction
Building codes regulate: the type of construction based on
o intended use,
o structure size,
o the prescence or lack of an automatic fire suppression system
what determine the type of building construction
The construction materials and their resistance to fire exposure
what code does Canada follow
Canada uses National model construction codes
5 types of construction
Type I through V which are further divided into subcategories depending on code and construction type
what defines each type of building type
The construction materials and performance when exposed to fire define each construction type
Type I and purpose
(fire resistant)
- Provides highest level of protection from fire spread as well as structural collapse
- Composed of noncombustible or limited combustible materials with high fire resistive rating
- Can be expected to remain structurally stable longer during fire and most collapse resistant
type I composed of
reinforced concrete
precast concrete
protected steel
Reinforced concrete
concrete that is internally fortified with steel reinform=cement bars or mesh placed within the concrete before it hardens
precast concrete
concrete building member is poured and set according to specification in a controlled environment and is then shipped to the concrete site for use
protected steel
steel structural members that are covered with either spray on fire proofing or fully encased in an underwiters laboratories tested and approved system
type I is often incorrectly reffered to as being…. but isn’t because….
fireproof
o While the structure wont burn it may degrade from the effects of fire
o Additional coimbustible materials in the building can generate sufficient heat over time to weaken buildings integrity
During a fire in a Type I structure firefighters may experience the following:
o Compartments can retain heat, contributing to the potential for rapid fire development
o Roofs may be extremely difficult to penetrate for ventilation purposes due to construction material and design
o Windows may be nonoperating causing them to be very difficult to open for ventilation
Type II and purpose
- Composed of materials that will not contribute to fire development or spread
- Do not meet the stricter requirements of those materials used in Type I building classification but still do not add to fuel load
materials used in Type II
metal framing members,
o metal cladding, or concrete block wall construction
o unprotected open web joists supporting metal roof decks
Type III and purpose
(ordinary construction)
- Commonly found in mercantile, business and residential structures and older schools
- Requires that exterior walls and structural members be constructed non combustible or limited combustible materials
type III materials
exterior walls and structural members be constructed non combustible or limited combustible materials
- Interior walls, collums, beams, floors and roofs completely or partially constructed of wood
type III - May contain a number of conditions that can influence fire behaviour including:
o Void channels inside the wooden channels that roof and truss systems create between wall studs are less protected than in type I and II construction
Fire will spread through these spaces unless fire stops are installed in the void
o Prefabricated wood truss systems
These systems may fail quickly when exposed to fire
type IV and purpose
Heavy Timber)
- Characterized by use of large dimesnsioned lumber or laminated wood
- Extremely stable and resistant to collapse due to the sheer mass of their structural members
o When involved in a fire it’s the timbers’ own char that reduces heat penetration to the inside of the beam
Type IV material
- Exterior walls are constructed of non combustible materials
- Interior building elements are constructed of solid or laminated wood with no concealed spaces, helping prevent unseen fire travel
- Glue laminated beams
- Glue laminated beams are part of what type of building and caution of them and where they are found
Type IV
- Glue laminated beams may fail when exposed to fire because the heat may affect the glue holding the laminates together
o Found in churches, auditorium, and other large facilities with vaulted or curved ceilings
Type IV buildings may contain the following conditions that can affect their behaviour during a fire
o The high concentration of wood can contribute to the intensity of a fire once it starts
o Collapse of masonary walls can be caused by the loss of structural integrity of timbers
Type V and purpose
- Examples: single family residences, some multistory apartment buildings
cheap
Type V materials
- Exterior load bearing walls are composed entirely of wood
- A venner of stucco, brick or stone may be constructed over the wood framing making it look like Type III
Depending on siding material, it may ——- to —- —- —- or —- —– —–
o Modern siding such as vinyl adds another petroleum based fuel to the structural fire load producing dense, dark, oily, toxic smoke
o The siding covers combustible insulation which becomes exposed when the siding melts away and may contribute to rapid fire development on the exterior and may extend to interior
- Depending on siding material, it may contribute to exterior fire spread or help minimize fire spread
Use of prefabricated wood truss sytem in place of solid floor joists create….
- Use of prefabricated wood truss sytem in place of solid floor joists create open void between floors
Wood i-beams and what happens to them during fire conditions
are usually constructed of a central piece of thin plywood, have numerous holes cut in for wires to pass through
o Under fire conditions these fail and burn much more rapidly than solid lumbar
adhesives and industrial glues
used more frequently in type V
used to engineered structural members
no more or less reliable than other construction methods
Truss
structural member used to form a roof or floor framework trusses form triangles or combinations of triangles to provide maximum load bearing capacity with a min amount of material
Fire stops
solid materials such as wood blocks, used to prevent or limit the vertical and horizontal spread of fire and the products of combustion in hollow walls or floors, above false ceilings, in penetrations for plumbing or electrical installations, in penetrations of fire rated assembly or in cocklofts and crawl spaces
Factory Built Homes
Structures that are partially or completely built in factory and shipped to location on which they are to be installed
Manufactured (mobile) homes
- Most common type of factory built homes
Manufactured (mobile) homes follow what rules
- Required to conform to US department of housing and Urban Development standard
-Not required to conform to the model building codes
Constructed before —–have ——- fire resistance
1976 have less
After 1976 mobile homes include:
Factory installed smoke and CO alarms
Use of flame retardant materials in interior finishes
Use of lame retardant materials aound heating and cooking equipment
Installation of safer heating and cooking equipment
Installation of gypsum board rather than wood paneling in interior finishes
Factory installed fire suppression systems (sprinklers)
mobile homes in fire conditions
- Some lightweight building materials in some factory built homes are susceptible to early failure in a fire
o Does not make forced entry` easier because can breach walls - May be anchored directly to concrete slab or have open crawl space beneath them which provides an additional source of oxygen during fire
- Fire may spread quicker because of fewer internal walls
Other types of factory built homes
Modular homes
Panelized homes
Pre cut homes
Hybrid modular structure
Modular homes
Modular section is transported to site then attached to permanent foundation which may include full basement
must comply with same local building codes as site built homes
o Only 6% of factory built homes are modular
o Sections can be stacked vertically and connected horizontally in numerous ways
Panelized homes
assembled on site from pre constructed panels made of foam insulation sandwiched between sheets of plywood
o Panels are self supporting so framing members are unnecessary
Pre cut homes
consist of individual parts that are custom cut and must be assembled on site.
examples of pre cut homes
Variety of styles including:
o Pole houses
o Post and beam construction
o Log homes
o A-frames
o Geodesic domes
Hybrid modular structure
includes elements of both modular design and panelized design
o Modular core units such as bathrooms or mechanical rooms are constructed in factory, moved to the site and assembled. Pre constructed panels are then added to the modules
Floors at ground level may consist of
a concrete slab or a floor assembly made up of joists and deck over a crawl space or basement
Upper floors of a multistory consist of
joists and decking with ceiling attatched to the bottom
Top level consists of
ceiling, joists or rafters and the roof above
The space between the floor/ceiling or ceiling/roof may contain:
o Duct work or open air plenum
o Electrical or communications wiring
o Water or natural gas pipes
o Pipes for a fire suppression system
o Recessed lighting and audio speakers
o Fiberglass, cellulose, or foam insulation beneath the roof or under the floors to act as sound proofing
Floor assemblies may be constructed of a combination of materials. Floors may be:
o Poured reinforced concrete
o Cellular concrete over metal decking
o Finished wood, tile, or carpet surface over a wood subfloor attatched to metal or wood joists
ceiling assemblies may be constructed of a combination of materials
o Gypsum board
o Tin tiles
o Lath and plaster attatched joists, roof trusses or beams
Ceilings in corridors that are designated as exit or egress passageways will have what kind
have the same fire resistance rating as the walls in that corridor
Walls
- Define the perimeter of the building as well as divide it into compartments or rooms
Exterior walls may be wood or metal siding attatched to:
o Studs
o A single layer of concrete
o Concrete blocks
o Logs
Wall assemblies consist of
a bottom plate, top plate, vertical studs and horizontal braces and sandwhiched between two surfaces made of gypsum or lath and plaster
o The cavity that the two surfaces form may have insulation
Fire wall assemblies
include the wall structure, doors, windows and any other protected openings meeting the required protection rating criteria
Materials used to cover floors in high occupancy structures
o Rated to limit flammability
o Ratings indicated in hours
fire walls may be used to
separate two ajoining structures and can also divide large structures into smaller portions and contain a fire to a particular portion of the structure
how are fire wall protection reduced
o When home owners and contractors make unprotected hoes for wires,pipes etc the protection of the fire wall can be reduced or eliminated
most difficult walls to penetrate
Exterior walls and fire walls are the most difficult to penetrate when attempting forced entry
general dangers of basements and stairs
- Fire in basements can damage floor joists and load bearing walls supporting upper floor
- Stairs can provide a fall danger in low visibility
- Stairs can provide a flow path for the movement of air, fire gases, and smoke throughout a structure
Basement
- A floor of a structure that is either partially or fully below grade level
Fire in basements may be more hazardous than in other compartments because
limited means of ingress/egress and limited ventilation
in basements -Absence of dry wall reduces fire resistance of
the studs and joints making the structural members part of the fuel load in the space
Protected or enclosed stairs
Stairs in commercial or multifamily residential buildings are required to have called this because they are built to resist the spread of fire and smoke
Access or convenience stairs
stairs that are not required to be a part of egres system and typically connect no more than two levels
Stairs can be classified as either
interior or exterior stairs