COURSE OUTLINE. Introduction of Structure Fires PART II-Roof Construction PART III-Tactical Considerations

Transcription

1 ROOF OPERATIONS

2 COURSE OUTLINE Introduction PART I-Phases I of Structure Fires PART II-Roof Construction PART III-Tactical Considerations PART IV-Ventilation Ventilation Methods

3 INTRODUCTION A considerable portion of the annual loss of life and property is a direct result of the lack of timely, effective ventilation 80% of all fire fatalities are due to smoke inhalation More than one-half of the nations fire loss is a direct result of smoke and heat damage Ventilation has a direct effect on all aspects of fire fighting strategies

4 PART I PHASES OF STRUCTURE FIRES

5 PHASES OF STRUCTURE FIRES Structure fires progress through three basic phases: Incipient or Beginning Phase Steady State or Free-Burning Phase Hot Smoldering Phase

6 Phases of Fire THE INCIPIENT / BEGINNING PHASE Oxygen content approximately 21%. Carbon dioxide, sulfur dioxide, carbon monoxide and water vapor produced. The flame temperature can be above 1000 degrees, while room temperature may only be slightly elevated.

7 Phases of fire STEADY STATE / FREE-BURNING PHASE Adequate oxygen and fuel sustain free- burning and fire growth to the point of full involvement of area/room. Mushrooming Flashover

8 Phases of Fire STEADY STATE / FREE-BURNING PHASE Mushrooming Smoke and gases are heated. If confined to a room or building, they will rise to the uppermost level. Cooler air is displaced down towards the fire, providing oxygen and sustaining combustion. As circulation occurs, heated smoke and gases build internal pressure that continue to rise and spread laterally.

9 Phases of Fire STEADY STATE / FREE-BURNING PHASE Flashover A simultaneous ignition over the surface of the room or area. Occurs when the heat from the fire raises the temperature of the contents to their ignition temperatures. The ignition happens in an instant. Effects may be deadly to firefighters

10 Phases of Fire HOT SMOLDERING PHASE If the free-burning state remains un-vented, the fire progresses into the hot smoldering phase. Low oxygen levels with little or no flame production. Temperatures in excess of 1000 degrees. Dense black smoke, that pressurizes the area. Intense heat continues to vaporize lighter fuels. These gases greatly increase the chance of a backdraft.

11 Phases of Fire HOT SMOLDERING PHASE Backdraft A confined area that is teeming with pressurized, heated and flammable gases. The introduction of oxygen to this fuel-rich environment will result in an explosion of significant intensity. Effects may be deadly to firefighters

12 Part II ROOF CONSTRUCTION

13 Roof Construction The firefighters ability to safely and efficiently ventilate a building through the roof will depend to some degree on his understanding of roof construction It is essential that firefighters become familiar with the existing and newly constructed buildings within their response area

14 Roof Construction Conventional VS Lightweight

15 CONVENTIONAL CONSTRUCTION

16 Roof Construction Conventional Construction Structural members depend on size for strength. Less surface area exposed to fire. The larger the size of a structural member, the longer it will take to fail when exposed to fire. Potentially longer burn time results in a greater window of safety for fire fighters.

17 Roof Construction Arched Trusses Buildings built during the 1930 s s and 1940 s s commonly used truss construction. Truss members have the same strength relationships as lightweight only much stronger.

18 Roof Construction Bridge Trusses Buildings built in the 1920 s s not as common as the arch Roofs vary in size and slightly in design Top surface is basically a flat roof

19 Roof Construction Conventional Residential

20 Roof Construction Conventional Residential

21 Roof Construction RAFTERS AND SPACE SHEETING

22 Roof Construction Conventional Construction Firefighter Concerns Generally sound construction Strongest areas of these roofs are ridges, hips, valleys, over trusses and where rafters cross outside walls Size of structural member dictates fire exposure time prior to failure Heat holes are acceptable and preferred with this type of construction

23 Roof Construction LIGHTWEIGHT CONSTRUCTION

24 Roof Construction Lightweight construction: Does not derive its strength from size. Strength obtained from multiple members in compression and tension. Involves the use of less fire resistive materials. Provides less time to ventilate before the roof becomes unstable.

25 Roof Construction Lightweight Construction General Rules Expect early and complete collapse No heat holes Cut vent holes well ahead of fire 3/8-1/2 1/2 decking offers little resistance to fire Time on these roofs is very limited

26 Roof Construction Major types of Lightweight roof construction Metal Gusset Plate Trusses. Wooden I Beam. Open Web Truss. Open Web Steel Joist Panelized

27 Roof Construction Metal Gusset Plate Trusses: Common in residential and commercial buildings. Usually 2 2 x 4 4 lumber butt jointed and held together by metal gusset plates commonly known as gang nail which are 3/8 in depth. Characterized by a top (compression) chord and bottom (tension) chord. Spans up to 80 with trusses 2 2 on center

28 Roof Construction Lightweight Commercial Metal gusset plate

29 Roof Construction Metal Gusset Plates

30 Roof Construction Metal Gusset Plates Burn test-structural structural collapse 1min. 20 sec.with direct flame impingement

31 Roof Construction Metal Gusset plates Firefighter Concerns Gusset plates increase charring at joints resulting in failure Bottom chord or web failure causes truss failure Open space between chords promotes fire spread

32 Roof Construction Wooden I Beam: Top and bottom chord of 2 2 x 3 3 or 2 2 x 4. The stem is normally 3/8 plywood or OSB glued in place. Common spacing is 2 2 on center. Strongest location is where the roof meets the exterior wall.

33 Roof Construction Wooden I Beam

34 Roof Construction Wooden I Beam Burn test-structural structural collapse 3 min. 15 sec. With direct flame impingement.

35 Roof Construction Wooden I Beam Firefighter Concerns Stem has very little relative mass and burns to failure quickly. Poke through construction reduces truss strength and promotes fire spread

36 Roof Construction Open Web Trusses: Wooden top and bottom chord cross connected by steel tube web members. 2x3 or 2x4 chords with spans of up to 70. Normal spacing is 2 2 on center. Strongest location is where the roof meets the exterior wall.

37 Roof Construction Open web Free hanging bottom cords

38 Roof Construction Open Web Trusses: Structural collapse 4 min. 30 sec. With direct flame impingement.

39 Roof Construction Open Web Trusses Firefighting Concerns This is the most lightweight of truss construction Steel is good conductor of heat Open space between cords promotes fire spread

40 Roof Construction Open Web Steel Joist Steel top and bottom chords usually 1/8 angle iron Webs 1/8 angle iron or 5/8 solid bars Corrugated metal decking is commonly used with these trusses Often configured in a panelized fashion

41 Roof Construction Open Web Steel Joist

42 Roof Construction Open Web Steel Joist

43 Roof Construction Open Web Steel Joist Firefighter Concerns Steel exposed to heat can distort and fail Consider rotary saws with carbide blades for cutting steel decking Fire may travel in horizontal openings of metal decking

44 Roof Construction Panelized Construction Consist of large, laminated beams spaced 12 to 40. Beams can span well over 100. Purlins with metal hangers on 8 8 centers. Purlins may be timber or truss design 2 x 4 4 rafters 2 2 on centers. Decking is usually 1/2 plywood.

45 Roof Construction Panelized Construction

46 Roof Construction PANELIZED SKELETON

47 Roof Construction Panelized roofs: Structural collapse 5 min. 20 sec. With direct flame impingement

48 Roof Construction Panelized Construction Firefighter Concerns Steel beam supports weaken and fail resulting in sudden collapse of large portions of roof Foil insulation adds to fire spread Strongest areas are over beams, purlins and perimeter of building

49 ROOF CONSTRUCTION Roof Styles and Designs

50 Roof Styles There are three basic styles of roof design Pitched roofs Arched roofs Flat roofs

51 Roof Styles Pitched Roof Design Gable Hip Shed Bridge Truss Mansard Gambrel

52 Roof Styles Gable Basic A-frame A design with the roof pitched in two opposing planes. May utilize conventional or lightweight construction. Covered by shake, tile, rock, composition, etc. and supported by sheathing or plywood.

53 Roof Styles PITCHED ROOF LINES

54 Roof Styles Pitched Roof with dormers

55 Roof Styles Hip Similar to the gable roof, but lacks the A-A frame configuration. Two sets of opposing pitches where the roof slopes down to meet every outside wall. May utilize conventional or lightweight construction.

56 Roof Styles Hip Roof

57 Roof Styles Shed This style is essentially half a gable roof. May utilize conventional or lightweight construction.

58 Roof Styles Bridge Truss Easily identified by its characteristic sloping ends. Wooden truss members are 2 2 x 12 and constitute a heavy grade of construction. Rafters are 2 2 x 6 6 or larger and covered by 1 1 x 6 6 sheathing and composition.

59 Bridged truss concealed by supported facade

60 Roof Styles Bridged Truss

61 Roof Styles Bridge Trusses

62 Roof Styles Bridge Trusses

63 Roof Styles Mansard This roof has a double slope on each of its four sides. The lower slope is steeper than the upper slope.

64 Roof Styles Arched Roof Design Ribbed arch Lamella roof Bowstring arch

65 Gambrel Pitched roof with two plans on each side Lower plans are steeper than upper plan Difficult to ladder, roof ladder usually required Lower plan may make up interior wall

66 Gambrel

67 Roof Styles Ribbed Arch Truss Similar to Bridge Truss except that the top chord is arched. Large wooden members of 2 2 x 12 to 2 2 x 14. Rafters (2 x 6 6 or more) are covered with 1 1 x 6 6 sheathing and composition roofing material. Early collapse is not a primary concern.

68 Roof Styles Arched Truss Roofs

69 Roof Styles Arched Trusses

70 Roof Styles Arched Trusses

71 Roof Styles Arched Truss This roof predictably fails in sections.

72 Roof Styles Lamella Roofs Egg-crate, geometric or diamond-patterned roof. Roof decking is 1 x 6 sheathing. Common on gymnasiums, supermarkets and recreational buildings. Total roof collapse may occur if fire removes more than 20% of roof structure. Failure results from the domino effect.

73 Roof Styles Lamella Roof

74 Roof Styles Lamella Roof

75 Lamella Tell-Tail Tail sign Lamella continuous arch Bridge truss trailing ends

76 Roof Styles Bowstring Arch Similar in appearance to ribbed arch and lamella roofs, yet significantly different. Metal tie rods with turnbuckles offer lateral support and ensure that arch roof does not push the exterior walls outward. Rafters (2 x 10 ) ) are covered with 1 1 x 6 6 sheathing and composition roofing material. Primary hazard is early failure of the metal tie rods and turnbuckles.

77 Roof Styles Flat Roof Design Popular style for a wide variety of structures. It is also the most deceiving style. Although it is simplistic in appearance, it varies in construction methods and is often difficult (from the exterior appearance) to visually determine the method utilized, i.e.. Conventional/lightweight.

78 Roof Styles Flat Roof Design Conventional Wooden I beam Open web Open web bar joist Metal gusset plate Panelized (may be combined)

79 Conventional construction Flat residential

80 Roof Styles Flat commercial

81 Roof Styles Flat Commercial

82 Flat Commercial with high parapets

83 Roof Styles Live Roof Loads

84 You never know what you might find

85 PART III TACTICAL CONSIDERATIONS

86 Tactical Considerations The decision is not, should we ventilate, but rather, what type of ventilation should we use and how aggressive should we be.

87 Tactical Considerations Ventilation is the first step in gaining positive control of a fire building. Ventilation allows all subsequent operations such as search, rescue and fire attack to be much more safe and efficient.

88 Tactical Considerations Life hazard/search and rescue Location and extension of the fire Type of construction (strengths/weakness) Means of ingress/egress

89 Tactical Considerations An aggressive interior attack always has an increased life hazard risk

90 Tactical Considerations Life hazard/search and rescue Immediate ventilation Facilitate search and rescue Route heat and smoke away from operation Always consider benefit to attack crews

91 Tactical Considerations Location and extension of the fire Risk Vs Gain Offensive/ Defensive Self vented Coordination with fire attack

92 Tactical Considerations Type of construction Strengths and/or weakness. Conventional: Heat hole over area of involvement. Lightweight: Vent hole ahead of fire. Time/Manpower constraints.

93 Tactical Considerations Means of ingress/egress LCES Identify path of travel Identify work area Two means of egress

94 Tactical Considerations What the ventilation group needs most and almost never has is the commodity of time

95 Tactical Considerations To accurately estimate the amount of time that a roof can be considered structurally sound the following factors must be considered:

96 Tactical Considerations Time Considerations Type of construction How long the fire has been burning Fire severity Your experience Frequency of training

97 Tactical Considerations We re Go in to the roof!

98 Tactical Considerations Ventilation Size-Up Type and age of building Type of construction Location and extension of fire and Smoke Type of roof Special Hazards

99 Tactical Considerations Basic equipment requirements Minimum of two-person teams. Full safety clothing and SCBA. Pick head axe and power saw. Rubbish hook, pike pole, or other suitable tool. Communication equipment.

100 Tactical Considerations Laddering Consider the areas that offer strength, routes of travel and no horizontal openings: corners, pilasters, hips, etc. Minimum of two ladders to a roof, providing a primary and alternate way to exit. Determine the roof line and its effect on ladder operations. Additional ladders needed?

101 Tactical Considerations Ground and Roof Ladders

102 Tactical Considerations Extension Ladder

103 Tactical Considerations Ladder Options

104 Choose the right tool for the job! 20 straight is the ladder of choice for flat residential

105 Aerial Ladder

106 Tactical Considerations Reading the Roof What is the size and type of roof? Is any portion of the roof sagging? Are there ventilators or smoke vents, and are they issuing smoke and/or fire? Is fire showing through the roof? Does the roof utilize material which may be difficult to traverse? Are additional ladders needed. (steep pitch/parapets)

107 Tactical Considerations Diagnostic Methods Indicator Hole Curf cut Chainsaw Axe blade/pick Triangle cut Chainsaw Axe Leave a trail

108 Tactical Considerations Curf cut using chainsaw

109 Apply chain brake and plunge saw to remove insulation

110 Triangle indicator using chainsaw

111 Triangular indicator hole using an axe

112 Remove insulation using axe handle or other suitable tool

113 PANELIZED WITH INSULATING FOIL

114 Tactical Considerations Diagnostic Methods Determining the type of roof The following will assist in determining the type of roof surface that will support a ventilation operation: Pre-fire planning. Plug cut. Axe bounce. Inspection cut (45 degree).

115 Tactical Considerations Pre-fire planning A valuable aid in determining what types of roofs are in a company s s district Ventilation operations are simplified when personnel have prior knowledge of basic types of roofs and their construction.

116 Tactical Considerations Plug cut A small triangular piece of roofing material is removed Reveals the type of roof decking Can determine rafter direction Metal joists are 90-degrees to corrugations in metal deck roofs. Rafters are 90-degrees to the grain of sheathing

117 Tactical Considerations Axe bounce Utilized to determine the direction of wood sheathing. Strike the roof at 90-degrees or parallel to any exterior wall. Axe will stick when parallel to the grain and bounce when 90-degrees to the grain. Will also determine the direction of the rafters underneath the sheathing.

118 Tactical Considerations Inspection cut Approximate area to be vented. Determine size and direction of rafters. Indication of fire intensity in rafter/truss area. 45 deg. To outside wall. One foot past structural member. Complete triangle. Remove piece over rafter.

119 Inspection Cut

120 Inspection hole 45 deg. To outer wall. Continue until rafter is rolled

121 Cut triangular shaped hole, ensure all cuts intersect

122 Tactical Considerations Inspection Hole

123 PART IV VENTILATION METHODS

124 Ventilation Methods Heat hole Close to area of involvement Most direct path for heat and smoke Dangerous procedure Not recommended with lightweight

125 Ventilation Methods Heat Holes over the fire near the peak

126 Ventilation Methods Heat hole flat roof

127 Ventilation Methods Directional Openings Strip ventilation opened ahead of the fire. Designed to change the horizontal direction or extension of fire, heat and smoke. Reduces or curtails horizontal spread

128 Ventilation Methods WIB STRIP CUT AGAINST CONSTRUCTION

129 VENTILATION METHODS Making the Cut

130 Ventilation Methods Center Rafter Technique Most universal cutting technique Building block of most all vent holes Hole size easily increased /extended Sections are cut so that they are nailed to only one rafter

131 Center Rafter

132 Center Rafter

133 Center Rafter

134 Ventilation Methods Center Rafter

135 Center Rafter Louver

136 Center rafter holes can easily be extended

137 Ventilation Methods Dicing Technique Head cut across several rafters Dice cut between rafters Decking can be pulled back or louvered

138

139 Multiple rafters can be rolled and marked to allow for dicing later

140 Dice cut between rafters

141 Panels can then be louvered or removed

142 Multiple center rafter cuts allow for various size vent holes

143 Ventilation Methods Louvering Technique Can be used with most decking material After cutting deck position as to form louvers to facilitate smoke removal

144 Panel louvers working from purlins against construction

145 Ventilation Methods J Hook J hooking with the appropriate tool separates decking from the center rafter Creates pile of decking at base of hole

146 Ventilation Methods

147 Rubbish hook, pike pole, axe or other appropriate tool can be used

148 Ventilation Methods Pull-back Method Can be used on all decking types Completely remove decking from vent opening Prevent decking from falling into vent hole Preferred method for heat holes

149 Pull back decking to open vent hole and create workable pile of material

150 Ventilation Methods Panelized Construction Always work from primary structural members Variations of a center rafter can be used on most all roofs

151 Panelized roof showing beams and purlins

152 Ventilation Methods Panelized schematic

153 Panel louver

154 Panel louver

155 Ventilation Methods Louver from a beam

156 Louver strip from a beam

157 Special Thanks To Fire Station 170 For their dedication and hard work

158 Roof Operations Power point Created by Firefighter Specialist Craig Reed

159