Chapter 11: Roofs
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Questions and Answers

What type of roofs are the easiest for firefighters to work on?

  • Inverted roofs
  • Curved roofs
  • Pitched roofs
  • Flat roofs (correct)

    • Which type of roof can provide a false sense of security for firefighters?

  • Pitched roofs
  • Curved roofs
  • Geodesic domes
  • Flat roofs (correct)

    • What material is NOT typically used in constructing geodesic domes?

  • Steel (correct)
  • Bamboo
  • Concrete
  • Plywood

    • Which type of roof support system may have inverted trusses?

    <p>Inverted roofs</p> Signup and view all the answers

    Which roofing system is becoming less common due to requiring higher knowledge and skills, costly materials, and more construction time?

    <p>Conventional framing</p> Signup and view all the answers

    What is the purpose of a Ridgepole Collar Tie in a roof framing system?

    <p>Braces the roof against the uplift of wind</p> Signup and view all the answers

    In what scenario would the failure of any single element of a bowstring truss lead to catastrophic failure?

    <p>When dealing with heavy snow loads</p> Signup and view all the answers

    What is the primary purpose of a steel tie rod in an arch-supported roof?

    <p>Resist outward thrust between the two ends of the arc</p> Signup and view all the answers

    Which material is commonly used in the construction of roof decks due to its nailability?

    <p>Plywood</p> Signup and view all the answers

    What is one of the conditions roofing materials must resist as mentioned in the text?

    <p>Resistance to hail storms</p> Signup and view all the answers

    What material are rafters commonly made of in contemporary commercial construction?

    <p>Wood</p> Signup and view all the answers

    What is the typical spacing range for wood rafters in construction?

    <p>12 to 24 inches</p> Signup and view all the answers

    What is the main difference between an inverted truss and a standard truss design?

    <p>Inverted trusses have beams under compression, whereas standard trusses have beams under tension</p> Signup and view all the answers

    What is the function of a ridge board in roof framing?

    <p>To provide vertical support to the rafters</p> Signup and view all the answers

    How does pre-engineered roof framing compare to beams or joists in terms of material usage?

    <p>Pre-engineered framing uses less material than beams or joists</p> Signup and view all the answers

    Why are new roofing materials sometimes added over an existing roof?

    <p>To repair sections of damage and update materials at a minimum cost</p> Signup and view all the answers

    What is a common issue associated with layered roofs due to the extra thickness of roofing materials?

    <p>Obstruction in ventilation and access operations</p> Signup and view all the answers

    Which material is commonly used as a drainage layer for built-up roofing systems?

    <p>Gravel aggregate</p> Signup and view all the answers

    Why are wood shingles and shakes made from red cedar, white cedar, or redwood?

    <p>Due to their resistance to decay</p> Signup and view all the answers

    What is the purpose of installing underlayment before applying asphalt shingles on a roof?

    <p>To provide cushioning and protect from wind-driven rain</p> Signup and view all the answers

    What is a disadvantage of wood shingles and shakes in terms of fire resistance?

    <p>They can easily ignite when exposed to burning brands</p> Signup and view all the answers

    How do clay, slate, and cement tiles differ from wood shingles in terms of fire resistance?

    <p>They are noncombustible and produce fire-resistant roof coverings</p> Signup and view all the answers

    What is one way to avoid galvanic corrosion in metal roof coverings?

    <p>Using nails made of a different metal as the sheeting</p> Signup and view all the answers

    What could be a consequence of painting or staining wood shingles or shakes with oil-based materials?

    <p>Reduced effectiveness of any fire treatment on the wood</p> Signup and view all the answers

    In the installation of slate roofing, how should the nail be positioned for proper installation?

    <p>Just touching the slate so that it hangs from the nail</p> Signup and view all the answers

    What is the purpose of roofing felt in flat metal roofing systems?

    <p>Acting as an insulating layer</p> Signup and view all the answers

    Why can firefighting on roofs with two separate layers pose challenges?

    <p>Difficulty in detecting products of combustion</p> Signup and view all the answers

    What is a potential hazard associated with green design roofs?

    <p>Weight increase due to added elements</p> Signup and view all the answers

    Why should photovoltaic cells be handled with care during fireground operations?

    <p>To avoid electrical charge transfer to metal roofing materials</p> Signup and view all the answers

    What is a key benefit of green roofs according to the text?

    <p>Improved oxygen-carbon dioxide exchange in urban areas</p> Signup and view all the answers

    What is a primary hazard associated with vegetative roofs if the vegetation is not properly taken care of?

    <p>Added fire load</p> Signup and view all the answers

    What is the primary purpose of penthouses constructed on the main roof of a building?

    <p>To provide additional living space</p> Signup and view all the answers

    What is the main function of skylights in a building?

    <p>To provide natural lighting</p> Signup and view all the answers

    Why are roof openings typically provided in buildings?

    <p>For roof access and ventilation</p> Signup and view all the answers

    What is a key consideration for skylights as per building codes?

    <p>The type of glass used for construction</p> Signup and view all the answers

    In what situations might skylights be equipped with photovoltaic strips?

    <p>For electronic operation</p> Signup and view all the answers

    Why must firefighters sometimes locate a route to access a roof in certain buildings?

    <p>When ladders cannot reach the roof level</p> Signup and view all the answers

    What can skylights be equipped with to allow for normal building ventilation?

    <p>Spring-loaded mechanisms</p> Signup and view all the answers

    What is the purpose of penthouses constructed on building roofs that contain stairwells?

    <p>To enable firefighters rapid roof access</p> Signup and view all the answers

    In what situation would firefighters resort to breaking or prying skylights during an emergency?

    <p>When no other escape options are available</p> Signup and view all the answers

    What is the primary purpose of a ridge board in roof framing?

    <p>To secure the upper ends of the rafters in a pitched roof</p> Signup and view all the answers

    What is the key characteristic that differentiates an inverted truss from a standard truss design?

    <p>The direction of the triangular portion projection</p> Signup and view all the answers

    Why are Pre-engineered roof trusses favored over beams or joists in construction?

    <p>They require less material and are lighter</p> Signup and view all the answers

    If wood rafters are spaced 18 inches apart in construction, what could this spacing indicate about the span and load?

    <p>A shorter span with a lighter design load</p> Signup and view all the answers

    In what way does an inverted truss challenge traditional truss designs in terms of structural compression?

    <p>By placing the standard portions of the truss under compression</p> Signup and view all the answers

    Given the purpose of Ridgepole Collar Tie in a roof framing system, where is this member typically located?

    <p>In the top third of the framing system</p> Signup and view all the answers

    What is a distinguishing feature of bowstring trusses that contributes to their structural stability?

    <p>They use a curved top chord</p> Signup and view all the answers

    Which material is commonly used to fabricate roof trusses and is found in both steel and wood options?

    <p>Fink and Pratt</p> Signup and view all the answers

    What is a key factor that influences the choice of roof covering material?

    <p>The slope of the roof</p> Signup and view all the answers

    Which type of roof decking material is known for its nailability and is frequently used due to this characteristic?

    <p>Plywood</p> Signup and view all the answers

    What is the primary purpose of adding new roofing materials over an existing roof?

    <p>Repairing sections of damage</p> Signup and view all the answers

    Which factor influences the choice of roof covering due to its ability to minimize the possibility of water pooling on a pitched roof?

    <p>Water drainage</p> Signup and view all the answers

    In flat roof coverings, what component is responsible for reducing heat loss through the roof?

    <p>Thermal insulation</p> Signup and view all the answers

    Which type of roofing membrane is made of several overlapping layers of roofing felt, saturated with a bituminous material?

    <p>Built-Up Membranes</p> Signup and view all the answers

    What component in flat roofs allows for the free movement of rainwater to the roof drains?

    <p>Drainage layer</p> Signup and view all the answers

    What is a key consideration for firefighters when working on pitched roofs with steep roof pitches?

    <p>Interacting with slick roofing materials</p> Signup and view all the answers

    What potential danger do flat roofs pose for firefighters?

    <p>Loose or broken pieces of roof tiles sliding off</p> Signup and view all the answers

    What is the primary difference between flat roofs and pitched roofs that may affect how firefighters interact with them?

    <p>Pitched roofs have inclined surfaces that may vary in slope</p> Signup and view all the answers

    Which type of roof support system uses inverted trusses, differing from conventional roof structures?

    <p>Inverted Roofs</p> Signup and view all the answers

    What should firefighters be cautious about when working on flat roofs to avoid misinterpreting the situation?

    <p>Deflection or vibration under their weight</p> Signup and view all the answers

    What is a key advantage of clay, slate, and cement tiles over wood shingles and shakes in terms of fire resistance?

    <p>They are noncombustible materials</p> Signup and view all the answers

    Which material is NOT commonly used for metal roof coverings as mentioned in the text?

    <p>Plastic</p> Signup and view all the answers

    What issue may arise if wood shingles or shakes are painted or stained with oil-based materials?

    <p>Reduced effectiveness of any fire treatment</p> Signup and view all the answers

    What is the main cause of galvanic corrosion in metal roof coverings?

    <p>Contact between dissimilar metals</p> Signup and view all the answers

    How does slate roofing differ from wood shingles in terms of potential longevity?

    <p>Slate has a life expectancy of 150 years</p> Signup and view all the answers

    What is the purpose of seams in individual flat metal roofing sheets?

    <p>To create a watertight seal</p> Signup and view all the answers

    How do green design roofs impact ventilation practices and indicators of fire location and spread?

    <p>Interfere with ventilation practices</p> Signup and view all the answers

    Why should photovoltaic cells be handled with care during fireground operations?

    <p>They store and generate electric power continuously</p> Signup and view all the answers

    What is a significant hazard associated with photovoltaic systems on flat roofs?

    <p>Transferring an electrical charge to metal roofing</p> Signup and view all the answers

    How do vegetative green roofs affect the insulation of a building?

    <p>Increase insulation between the building and its environment</p> Signup and view all the answers

    What is a primary consideration when firefighters need to access a roof from inside a building?

    <p>Locating a route to access the roof</p> Signup and view all the answers

    What is the primary function of skylights according to the information provided?

    <p>Supplying natural lighting to the interior</p> Signup and view all the answers

    In what situation might firefighters use roof openings during fire fighting?

    <p>For quick roof access or ventilation</p> Signup and view all the answers

    What hazard might arise if vegetative roofs lack proper hydration?

    <p>Increased fire load</p> Signup and view all the answers

    What is a common material used in the construction of skylights?

    <p>Tempered glass or plastic</p> Signup and view all the answers

    Why might penthouses be constructed on building roofs according to the text?

    <p>For mechanical equipment storage</p> Signup and view all the answers

    What is one impact of green roofs being constructed with a layer of earth and growing plants?

    <p>Increased fire resistance</p> Signup and view all the answers

    How do skylights typically facilitate building ventilation?

    <p>By opening for air circulation</p> Signup and view all the answers

    What is an essential feature of some skylights that allows for electronic operation?

    <p>Spring-loaded mechanisms</p> Signup and view all the answers

    Why might skylight housing need to be pushed aside in an emergency?

    <p>To facilitate roof access for firefighters</p> Signup and view all the answers

    Study Notes

    Roofs and Fire Fighting

    • A roof is a waterproof covering for a building that plays a crucial role in structural fire fighting.
    • Firefighters must be familiar with roof construction, including the use of a roof to support ventilation equipment.

    Safety Points Regarding Roofs

    • Roofs are usually not as strong as floors.
    • Roofs may have concealed spaces.
    • Roofs are subject to wear and deterioration.

    Types of Roofs

    • Flat Roofs: Found on various types of buildings, provided with a slight slope for drainage, and are the easiest roofs for firefighters to work on.
    • Pitched Roofs: Designed to shed water and snow, have a slope that presents a major hazard to firefighters, and can be categorized into low slope roofs and medium to high slope roofs.
    • Curved Roofs: Include geodesic domes, which are created using spherical triangulation.

    Roof Support Systems

    • Flat Roof Support: May use open-web steel joists and steel beams, or ordinary wood joists supported at either end by load-bearing walls.
    • Pitched Roof Support: Uses inclined members to support pitched roofs, built on site utilizing dimensional lumber.
    • Roof Trusses: Use lightweight wood trusses, which are commonly used in many types of structures.

    Roof Trusses Materials

    • Wood: Fabricated from wood, including plywood, wood planks, and laminated wood.
    • Steel: Fabricated from steel, including corrugated steel, precast concrete, and poured gypsum.

    Roof Decks

    • Definition: Serve several purposes, including separating the structure from the effects of weather and supporting the weight of the materials used to weatherproof the structure.
    • Materials: Include plywood, wood planks, corrugated steel, precast gypsum or concrete planks, poured gypsum, poured concrete, and cement planks containing wood fiber.

    Roof Coverings

    • Purpose: Provide a water-resistant barrier for the roof system.
    • Types: Include built-up membranes, single-ply membranes, fluid-applied membranes, and shingles.

    Factors Affecting Roof Covering Choice

    • Maintenance requirements
    • Durability
    • Wind resistance
    • Fire resistance

    Layered Roof Coverings

    • Extra thickness: Can impede progress during ventilation and access operations.
    • Reasons: Repair sections of damage, update the roofing materials at a minimum of cost and disruption, and cheaper and faster than replacing the existing roof.

    Components of Flat Roof Coverings

    • Vapor barrier: Reduces diffusion of interior moisture into the insulation layer.
    • Thermal insulation: Reduces heat loss through the roof.
    • Roofing membrane: Keeps out rain and snow from the interior of the building.
    • Drainage layer: Permits the free movement of rainwater to the roof drains.
    • Wear course: Protects the roof from mechanical abrasion.

    Pitched Roof Coverings

    • Water drainage: Water immediately drains from a pitched roof, minimizing the possibility of it pooling on the roof.
    • Types: Include shingles and metal roof coverings.

    Installation of Roof Coverings

    • Shingles: Installed over an underlayment, which serves as a cushion and provides protection from wind-driven rain.
    • Shakes: Installed with an overlap so only one-third of the surface of the shake is exposed to the weather.

    Challenges of Firefighting on Roofs

    • Products of combustion: Can be difficult to detect, access, and extinguish when they enter the void space in a roof.
    • Two separate roofs: Can impede rapid and effective ventilation.
    • Small spaces: Can create an entrapment hazard for firefighters.

    Green Design Roofs

    • Increased energy efficiency: Is the greatest benefit of this style of roof.
    • Added elements: Can increase the weight of the roof, which can be a hazard if the structural supports are not adequate.

    Photovoltaic Roofs

    • Energy feed: Cannot be isolated or shut off, and should be handled with the same care as any other electrical system.
    • Hazard: Can transfer an electrical charge to metal roofing materials if the supports and other components are compromised.

    Vegetative Roof Systems

    • Definition: A roof of a building that is partially or completely covered with vegetation and a growing medium, planted over waterproof roofing elements.
    • Benefits: Include increased insulation between the building and its environment, and the increase in air quality due to the oxygen-carbon dioxide exchange of growing plants.### Hazards of Vegetative Roofs
    • Vegetative roofs can be a fire hazard if not properly hydrated or if fertilizers are improperly stored.

    Roof Openings

    • Roofs may have openings for purposes such as penthouses, skylights, and ventilation.
    • These openings can be used for firefighting and roof access.

    Skylights

    • Skylights provide natural lighting to the interior of a building.
    • They can be located to serve only the top story of a building or over an atrium, stairwell, or light shaft.
    • Building codes restrict the materials used in skylights.

    Roof Framing Components

    • Rafter: an inclined beam that supports a roof, runs parallel to the slope of the roof.
    • Ridge Board: the highest horizontal member in a pitched roof to which the upper ends of the rafters attach.
    • Collar Tie: a horizontal roof framing member in the top third of the framing system; braces the roof framing against the uplift of wind.
    • Rafter Tie: a horizontal roof framing member at the bottom of the roof framing system; helps keep walls from spreading due to the weight of the roof.

    Roof Trusses

    • Several types of roof trusses may be used to support roofs.
    • Lightweight wood trusses are commonly used in many types of structures.
    • Joints used in trusses often are connected using gang-nail type gusset plates.

    Bowstring Trusses

    • Bowstring trusses use a curved top chord and were once commonly used for roofs.
    • The two elements of bowstring trusses work together to maintain structural stability.

    Roof Decks

    • Roof decks serve several purposes, including separating the structure from the effects of weather and supporting the weight of the materials used to weatherproof the structure.
    • Materials used in the construction of roof decks include plywood, wood planks, corrugated steel, precast gypsum or concrete planks, and poured gypsum or concrete.

    Roof Coverings

    • Roof coverings provide the water-resistant barrier for the roof system.
    • The type of roof covering used depends on the form of the roof structure, the slope of the roof, the local climate, and the appearance desired.

    Firefighters and Roofs

    • Firefighters must be familiar with roof construction, including the use of a roof to support ventilation equipment.
    • Safety points regarding roofs: they are usually not as strong as floors, may have concealed spaces, and are subject to wear and deterioration.

    Pitched Roofs

    • Pitched roofs are designed to shed water and snow and have a slope that presents a major hazard to firefighters.
    • Care must be taken when interacting with pitched roofs, especially on steep roof pitches and slick roofing materials.

    Flat Roofs

    • Flat roofs are provided with a slight slope for drainage.

    • They are the easiest roofs for firefighters to work on, but can provide a false sense of security and have potential dangers such as pools of water, openings, and low parapets.### Flat Roofing Sheets

    • Flat roofing sheets are nailed to a deck beneath, with a layer of roofing felt placed on the metal deck to increase fire resistance and protect the wood deck from external fires.

    • Individual flat sheets of metal roofing are joined at seams and crimped watertight, with seams standing up vertically at the joint between adjacent sheets.

    Fire Ratings of Roof Coverings

    • Building codes impose restrictions on the combustibility of roofs based on occupancy, location, and other factors.
    • Test procedures are contained in NFPA 2.

    Challenges of Firefighting on Roofs

    • Products of combustion can enter the void space in a roof, making it difficult to detect, access, and extinguish.
    • Small spaces between two roofs can create an entrapment hazard for firefighters.
    • The rain roof may not be structurally solid enough to support the weight of firefighting operations.

    Green Design Roofs

    • Increased energy efficiency is the greatest benefit of green design roofs.
    • Added elements can increase the weight of the roof, which can be a hazard if structural supports are not adequate.
    • Systems can interfere with ventilation practices and indicators of fire location and spread.

    Photovoltaic Roofs

    • Photovoltaic (PV) systems produce reliable, clean energy.
    • The energy feed from photovoltaic cells cannot be isolated or shut off and should be handled with care.
    • Photovoltaic cells may not be readily identifiable on flat roofs or in low light, adverse weather, or during fireground operations.
    • Raised panels can create a significant traction, tripping, and falling hazard.

    Hazards of Photovoltaic Systems

    • Photovoltaic cells continue to store and generate electric power even when electric power to the building is shut off.
    • PV systems can transfer an electrical charge to metal roofing materials if supports and other components are compromised.

    Photovoltaic Systems and Green Roofs

    • Photovoltaic systems convert solar energy into direct current (DC) electricity.
    • Clean energy or sustainable energy meets the needs of current consumers without compromising future resources.
    • Green roofs can include vegetative roof systems, photovoltaic systems, and reflective surfaces.

    Vegetative Roof Systems

    • Benefits of green roofs include increased insulation and air quality due to oxygen-carbon dioxide exchange.
    • A rooftop garden constitutes a dead load on the roof structural system, requiring support capability.
    • Primary hazards of vegetative roofs include added fire load if vegetation is not properly hydrated or if fertilizers are improperly stored.

    Roof Openings

    • Roof openings are provided for purposes other than fire protection, but can be used for roof access or ventilation during firefighting.
    • Penthouses provide rapid access to the roof from inside the building for firefighting.
    • Skylights can be used for natural lighting and can be located over the top of an atrium, stairwell, or light shaft.

    Skylights

    • Skylights are windows built into the ceiling or roof of a building and can be made of plastic, wired glass, or tempered glass.
    • Skylights can be equipped with operable glass panes for normal building ventilation.
    • Skylights can provide a rapid means of ventilating heat and smoke.
    • Skylights may also be equipped with photovoltaic strips for electronic operation.

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    Test your knowledge on roofs and their importance in structural fire fighting. Learn about roof construction, safety points, and different roof styles such as flat, pitched, and curved.

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