ROOF OPERATIONS
COURSE OUTLINE Introduction PART I-Phases I of Structure Fires PART II-Roof Construction PART III-Tactical Considerations PART IV-Ventilation Ventilation Methods
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
PART I PHASES OF STRUCTURE FIRES
PHASES OF STRUCTURE FIRES Structure fires progress through three basic phases: Incipient or Beginning Phase Steady State or Free-Burning Phase Hot Smoldering Phase
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.
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
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.
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
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.
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
Part II ROOF CONSTRUCTION
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
Roof Construction Conventional VS Lightweight
CONVENTIONAL CONSTRUCTION
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.
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.
Roof Construction Bridge Trusses Buildings built in the 1920 s-1940 1940 s not as common as the arch Roofs vary in size and slightly in design Top surface is basically a flat roof
Roof Construction Conventional Residential
Roof Construction Conventional Residential
Roof Construction RAFTERS AND SPACE SHEETING
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
Roof Construction LIGHTWEIGHT CONSTRUCTION
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.
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
Roof Construction Major types of Lightweight roof construction Metal Gusset Plate Trusses. Wooden I Beam. Open Web Truss. Open Web Steel Joist Panelized
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
Roof Construction Lightweight Commercial Metal gusset plate
Roof Construction Metal Gusset Plates
Roof Construction Metal Gusset Plates Burn test-structural structural collapse 1min. 20 sec.with direct flame impingement
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
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.
Roof Construction Wooden I Beam
Roof Construction Wooden I Beam Burn test-structural structural collapse 3 min. 15 sec. With direct flame impingement.
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
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.
Roof Construction Open web Free hanging bottom cords
Roof Construction Open Web Trusses: Structural collapse 4 min. 30 sec. With direct flame impingement.
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
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
Roof Construction Open Web Steel Joist
Roof Construction Open Web Steel Joist
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
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.
Roof Construction Panelized Construction
Roof Construction PANELIZED SKELETON
Roof Construction Panelized roofs: Structural collapse 5 min. 20 sec. With direct flame impingement
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
ROOF CONSTRUCTION Roof Styles and Designs
Roof Styles There are three basic styles of roof design Pitched roofs Arched roofs Flat roofs
Roof Styles Pitched Roof Design Gable Hip Shed Bridge Truss Mansard Gambrel
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.
Roof Styles PITCHED ROOF LINES
Roof Styles Pitched Roof with dormers
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.
Roof Styles Hip Roof
Roof Styles Shed This style is essentially half a gable roof. May utilize conventional or lightweight construction.
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.
Bridged truss concealed by supported facade
Roof Styles Bridged Truss
Roof Styles Bridge Trusses
Roof Styles Bridge Trusses
Roof Styles Mansard This roof has a double slope on each of its four sides. The lower slope is steeper than the upper slope.
Roof Styles Arched Roof Design Ribbed arch Lamella roof Bowstring arch
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
Gambrel
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.
Roof Styles Arched Truss Roofs
Roof Styles Arched Trusses
Roof Styles Arched Trusses
Roof Styles Arched Truss This roof predictably fails in sections.
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.
Roof Styles Lamella Roof
Roof Styles Lamella Roof
Lamella Tell-Tail Tail sign Lamella continuous arch Bridge truss trailing ends
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.
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.
Roof Styles Flat Roof Design Conventional Wooden I beam Open web Open web bar joist Metal gusset plate Panelized (may be combined)
Conventional construction Flat residential
Roof Styles Flat commercial
Roof Styles Flat Commercial
Flat Commercial with high parapets
Roof Styles Live Roof Loads
You never know what you might find
PART III TACTICAL CONSIDERATIONS
Tactical Considerations The decision is not, should we ventilate, but rather, what type of ventilation should we use and how aggressive should we be.
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.
Tactical Considerations Life hazard/search and rescue Location and extension of the fire Type of construction (strengths/weakness) Means of ingress/egress
Tactical Considerations An aggressive interior attack always has an increased life hazard risk
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
Tactical Considerations Location and extension of the fire Risk Vs Gain Offensive/ Defensive Self vented Coordination with fire attack
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.
Tactical Considerations Means of ingress/egress LCES Identify path of travel Identify work area Two means of egress
Tactical Considerations What the ventilation group needs most and almost never has is the commodity of time
Tactical Considerations To accurately estimate the amount of time that a roof can be considered structurally sound the following factors must be considered:
Tactical Considerations Time Considerations Type of construction How long the fire has been burning Fire severity Your experience Frequency of training
Tactical Considerations We re Go in to the roof!
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
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.
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?
Tactical Considerations Ground and Roof Ladders
Tactical Considerations Extension Ladder
Tactical Considerations Ladder Options
Choose the right tool for the job! 20 straight is the ladder of choice for flat residential
Aerial Ladder
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)
Tactical Considerations Diagnostic Methods Indicator Hole Curf cut Chainsaw Axe blade/pick Triangle cut Chainsaw Axe Leave a trail
Tactical Considerations Curf cut using chainsaw
Apply chain brake and plunge saw to remove insulation
Triangle indicator using chainsaw
Triangular indicator hole using an axe
Remove insulation using axe handle or other suitable tool
PANELIZED WITH INSULATING FOIL
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).
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.
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
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.
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.
Inspection Cut
Inspection hole 45 deg. To outer wall. Continue until rafter is rolled
Cut triangular shaped hole, ensure all cuts intersect
Tactical Considerations Inspection Hole
PART IV VENTILATION METHODS
Ventilation Methods Heat hole Close to area of involvement Most direct path for heat and smoke Dangerous procedure Not recommended with lightweight
Ventilation Methods Heat Holes over the fire near the peak
Ventilation Methods Heat hole flat roof
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
Ventilation Methods WIB STRIP CUT AGAINST CONSTRUCTION
VENTILATION METHODS Making the Cut
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
Center Rafter
Center Rafter
Center Rafter
Ventilation Methods Center Rafter
Center Rafter Louver
Center rafter holes can easily be extended
Ventilation Methods Dicing Technique Head cut across several rafters Dice cut between rafters Decking can be pulled back or louvered
Multiple rafters can be rolled and marked to allow for dicing later
Dice cut between rafters
Panels can then be louvered or removed
Multiple center rafter cuts allow for various size vent holes
Ventilation Methods Louvering Technique Can be used with most decking material After cutting deck position as to form louvers to facilitate smoke removal
Panel louvers working from purlins against construction
Ventilation Methods J Hook J hooking with the appropriate tool separates decking from the center rafter Creates pile of decking at base of hole
Ventilation Methods
Rubbish hook, pike pole, axe or other appropriate tool can be used
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
Pull back decking to open vent hole and create workable pile of material
Ventilation Methods Panelized Construction Always work from primary structural members Variations of a center rafter can be used on most all roofs
Panelized roof showing beams and purlins
Ventilation Methods Panelized schematic
Panel louver
Panel louver
Ventilation Methods Louver from a beam
Louver strip from a beam
Special Thanks To Fire Station 170 For their dedication and hard work
Roof Operations Power point Created by Firefighter Specialist Craig Reed