Building Construction Related to the Fire Service Chapter

Building Construction Related to the Fire Service Chapter 11 — Roofs

Building Construction 11– 1

Learning Objective 1 Identify the ways roofs can affect structural fire fighting. Building Construction 11– 2

Role in Fire Fighting • Work on top of roofs • Use as vantage point for attacking fire involving neighboring structure • Work beneath whenever inside a building Building Construction 11– 3

Safety Points • Roofs usually not as strong as floors • Inherent concealed spaces between ceiling and roof deck • Loads added over time that roofs were not designed to bear • Subject to wear and deterioration Building Construction 11– 4

Waterproof Quality • Limits penetration of streams from ladder pipes and platform apparatus • Forms waterproof covering over buried fire if collapses into a structure Building Construction 11– 5

Learning Objective 2 Describe the characteristics of the different architectural styles of roofs. Building Construction 11– 6

Flat Roofs • If completely horizontal, present drainage problems • Many have slight slope • May be sloped toward drains in center of roof • Easiest to work on, but potential danger in dark Building Construction 11– 7

Pitched Roofs • Have inclined surfaces – Low slope – Medium to high slope • Designed to shed water and snow • Hazards to firefighters Courtesy of Chris E. Mickal, NOFD Photo Unit Building Construction 11– 8

Styles of Pitched Roofs Building Construction 11– 9

Curved Roofs • Most frequently supported by arches and bowstring trusses • Dome • Geodesic domes • Dormer Building Construction 11– 10

Learning Objective 3 Describe the systems used to support roofs. Building Construction 11– 11

Flat Roof Support • Wood joists supported at either end by load-bearing wall • Solid wood joists lose strength gradually as they burn • Signs of structural failure • Thin plywood or OSB can fail quickly without warning (Continued) Building Construction 11– 12

Flat Roof Support • View any indication of heavy fire development as warning sign of structural failure • Box or I-beams of plywood and wood truss joists often used to support flat roofs Building Construction 11– 13 (Continued)

Flat Roof Support • Susceptibility to early failure • Vibration and deflection of roof • Inverted roof Courtesy of Mc. Kinney (TX) Fire Department Building Construction 11– 14

Raftered Roof • Rafter – Inclined joist that supports pitched roof – Runs parallel to slope – Results in outward thrust against walls – Commonly made of wood Building Construction 11– 15 Courtesy of Wil Dane

Trusses • Have reduced mass and interdependence of components • Early failure in fire • Ceilings suspended from roof truss create concealed spaces Courtesy of Dave Coombs Building Construction 11– 16

Arches • Behavior of roof supported by arch basically determined by material from which arch is constructed • May use steel tie rod between two ends of arc to resist outward thrust of arch Building Construction 11– 17

Learning Objective 4 Explain the functions of the roof deck and describe the materials used to construct it. Building Construction 11– 18

Function of Roof Decks • Portion to which roof covering is applied • Transmits loads of roof to supporting members • Concrete deck serves as roof support • Deck must not deflect excessively under anticipated loads Building Construction 11– 19

Materials • • • Plywood Wood panel Wood planks Corrugated steel Concrete Cement planks Courtesy of Mc. Kinney (TX) Fire Department Building Construction 11– 20

Learning Objective 5 Describe the types and materials used as roof coverings for the different types of roofs. Building Construction 11– 21

Function of Roof Coverings • Water-resistant barrier for roof system • Factors affecting choice – Form and slope of roof – Local climate – Appearance desired – Maintenance requirements – Durability – Required wind and fire resistance Building Construction 11– 22

Flat Roof Coverings Building Construction 11– 23

Pitched Roof Coverings • Function differently than flat roof coverings • Must be secured to roof deck or support to counter force of gravity (Continued) Building Construction 11– 24

Pitched Roof Coverings • Shingles and tiles – Wood shingles and shakes – Asphalt shingles – Slate – Clay tile – Concrete tiles Courtesy of Mc. Kinney (TX) Fire Department (Continued) Building Construction 11– 25

Pitched Roof Coverings • Application of shingles and tiles – Usually attached with corrosion-resistant nails – Wood shingles – Asphalt shingles – Slate tiles • Fire performance of various shingles and tiles Building Construction 11– 26

Metal Roof Coverings • Materials include galvanized iron or steel, copper, zinc, aluminum, and lead • Can use flat or corrugated metal • Corrugated sheets generally strong enough to install without decking • Layer or roofing felt placed on deck beneath metal sheets (Continued) Building Construction 11– 27

Metal Roof Coverings • Roofing felt increases fire resistance of wood decking • Metal roofs installed over existing wood roofs create void space Building Construction 11– 28

Metal Roof Coverings Courtesy of Ed Prendergast Courtesy of Mc. Kinney (TX) Fire Department Building Construction 11– 29

Learning Objective 7 Describe the characteristics of roofs installed for specific purposes. Building Construction 11– 30

Rain Roofs • A second roof constructed over older roof that is so deteriorated that it cannot be repaired • Void created between rain roof and original roof • Impedes rapid and effective ventilation (Continued) Building Construction 11– 31

Rain Roofs Building Construction 11– 32

Green Roofs • Designed to protect environment and • • conserve energy Benefits Can vary in use Constitutes a dead load Fire conditions Building Construction 11– 33 Courtesy of Ed Prendergast

Photovoltaic (PV) Roofs • Produce clean and reliable energy used in a wide range of applications • Panels on top of or embedded in roof • Hazards to fire fighting – Electrical shock – Inhalation exposure – Falls from roof – Roof collapse Building Construction 11– 34

Learning Objective 8 Discuss the purpose of penthouses and skylights and their impact on fire fighting tactics. Building Construction 11– 35

Penthouses • Structures on main roof of building • Used for: – Stairway enclosure – Elevator machinery enclosure – Mechanical equipment storage – Additional living space Building Construction 11– 36

Skylights • Natural lighting to building interior • Serve top story or located over top of an atrium, stairwell, or light shaft • Sometimes have operable glass planes; codes require wired or tempered glass • Rapid ventilating of heat and smoke; do not provide for automatic venting (Continued) Building Construction 11– 37

Skylights Courtesy of Mc. Kinney (TX) Fire Department Building Construction 11– 38

Learning Objective 9 Describe the impact ceilings have on fire spread to roofs. Building Construction 11– 39

Function of Ceilings • Diffuse light and distribute air in a room • Conceal air conditioning ducts, electrical wiring, and sprinkler piping Courtesy of Mc. Kinney (TX) Fire Department Building Construction 11– 40

Installation of Ceilings • Attached directly to underside of roof joists or trusses • Distance beneath roof supports creates considerable concealed space • New ceiling installed beneath existing ceiling in older buildings Building Construction 11– 41

Impact on Fire Fighting • Concealed space created in fire-resistive building may conceal type of roof structure above • Extent of fire development in roof spaces is hidden by ceiling Building Construction 11– 42

Know your Roofs! Building Construction 11– 43