Chapter 11: Roofs

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.