Ch. 11 Roofs Flashcards
Several fundamental safety points regarding roofs: (4)
Roofs are usually NOT AS STRONG as floors, designed to support lighter loads.
Inherent CONCEALED spaces, difficult to determine the extent to which a fire has developed overhead.
LOADS may be ADDED to roofs they for which they were not designed.
Roofs subject to wear and tear, repaired or renovated, SEVERAL LAYERS.
3 STYLES of roofs
Flat
Pitched
Curved
Flat roofs found on ________.
All types of buildings
Typical slope of many flat roofs:
Front to rear
Flat
Many LARGE buildings have roofs sloped toward:
Drains at the center of the roof
Flat roof are the ______ on which firefighters can work.
EASIEST roofs
These roofs can provide a false sense of security and are not without potential dangers.
Flat
Pitched roofs categorized into ____ roofs and ______ roofs.
Low slope
Medium to high slope
Low slope roofs have a slope of up to ________, meaning for each ____ units of ______ dimension, the roof slopes ______ ___ units.
3 to 12. 12. Horizontal. Upward. 3.
Medium to high slope roofs have slopes of ______ to ______. A slope of ______ equates to a ____ degree angle.
4/12
12/12
12/12
45
Some structures, such as certain churches and mansions, have roofs with slopes of _____ or greater
18/12
PITCHED roof styles determined by ____, ____ and _____.
Climate
Function
Aesthetic considerations
The simplest pitched roof is the ______ roof that slopes in only _________ direction.
Shed.
1
Very common roof style that consists of two INCLINED surfaces that meet at their high side to form a RIDGE
OR
Pitched roof with square ends, end walls form TRIANGULAR areas beneath roof
Gable
Slopes in FOUR DIRECTIONS
OR
No gables, all FACETS of roof slope down
Hip
have to be hip in all facets/4 directions
Slope in two directions but a break in the slope on each side
Functional because the space created by roof can be used as an attic/living space
OR
Style of gabled roof where each side slopes at two different angles
Gambrel
BREAK in the slope of the roof on ALL four SIDES
Can be constructed with flat deck (deck roof)
Roof forms a projection that creates a concealed space
OR
Have slopes at two different angles, ALL sides slope down
Mansard
Once commonly used on INDUSTRIAL buildings for light and ventilation. Glass vertical sections should face north because northern light more constant and glare of sun can be avoided.
OR
Alternating vertical walls
Sawtooth (industrial)
V-shaped roof, resembling two opposing shed roofs that meet at their low eaves OR
Roof style slopes in two directions
Butterfly
_____ and _____ have largely eliminated the need for monitor and sawtooth roofs.
Modern ventilation
Lighting systems
Designed to provide light and ventilation, commonly used on FACTORY buildings, vertical sides known as “clerestories”
Raised central section (exaggerated lantern roof)
Monitor (factory)
“Monitor from the clerestories”
The _____ of a roof presents a _______ to FFs because the steepness of the roof result in a lack of secure footing, which is increased when the roof is ____ or covered with ____ but also exists when the roof is ____.
Pitch
Major hazard
Wet
Ice
Dry
____ or ________ roof tiles can also slide off a pitched roof and create a hazard for FFs on the _____.
Loose
Broken pieces of
Ground
_____ roof surfaces take their form from the structural system used to support them.
Curved
Curved roofs are most frequently supported by _____ and ______.
Arches
Bowstring trusses
When the area to be enclosed by the roof is circular, a _______ roof can be used. A dome roof can be though of as an _____ rotated 360 degrees.
Dome
Arch
A dome roof produces structural forces similar to those of an _____. That is ______ exist at the base and a ________ exists at the top.
Arch
Horizontal thrusts
Compressive force
Most architecturally spectacular curved roofs can be created using _______ or ________.
Geodesic domes
Lamella arches
The _________ is a special form of arched roof, constructed from ________ of wood known as lamellas.
Lamella arch
Short pieces
Lamellas vary from _____ to ______ and in lengths varying from __ to __ feet.
2x8 inches
3x16 inches
8 to 14 feet
Short lamellas are bolted together in a ___________ with a special plate known as a ___________, with the curvature of the lamellas arch results from the _______________ of the ends of the individual lamellas.
Diagonal pattern
Lamella washer (plate)
Beveling (inclining)
Lamella technique can be adopted to form a ___ as well as an _____.
Dome
Arch
_____ is created using spherical triangulation. That is, triangles are arranged in _______ to form a nearly spherical surface.
Geodesic dome
Three dimensions
plywood and bamboo
_____ is frequently provided in buildings with pitched roofs to increase the _______ in an attic by increasing ____ and _____. They often become ______.
Dormer.
Usable space.
Light.
Ventilation.
Living space
Several methods to support flat ROOFS. The simplest system uses ______ supported on either end by ____.
Ordinary wood joists
Load bearing wall
The _________ function as beams to support the roof deck just as floor beams support a floor system.
Wood joists
Traditional wood-joisted roof uses ________ that tend to lose their strength ______ as they burn. Loss of strength result in a soft or spongy roof before failure, especially with a ______________.
Solid wood joists
Gradually
Wood plank roof deck
soft or spongy
Softening or sagging roof is an OBVIOUS indication of structural failure, it should NOT be looked upon as ___________.
The ONLY sign of imminent collapse
In general, FFs should view any indication of ____________ as a warning sign that the roof is WEAKENING.
Advanced or heavy fire development
Box beams and I-beams manufactured from plywood and wood truss joists. Although these beams provide adequate strength, the thin web portion of plywood I-beams renders them ___________ in a fire.
Susceptible to early failure
Open web design of truss joints also permits the rapid spread fire in directions __________ to the truss joist instead of simply along the dimension of the member.
Perpendicular
Fireproofing can be omitted from roof support when the roof is located ______________ above the floor in an assembly occupancy. (And still be Type I)
MORE than 20 feet
Not unusual for modern FLAT roofs to ______________ noticeably as personnel walk across them. __________ under the weight of firefighters ______ signal imminent failure but the _________ ARE an indication of lightweight roof construction and FFs should view such construction CAUTIOUSLY.
Deflect or vibrate.
Deflection or vibration.
May NOT.
Deflection and vibration
With conventional roof, the main joists are at the ______ level where as with the inverted roof, the main joists are located at the _________ and framework is constructed above the main joists.
Final roof level
Level of the ceiling
______ are the inclined joist used to support some types of pitched roofs. Rafters are the ______ support, although trusses can also be used.
Rafters
Standard
The basic design of a raftered roof results in an _______ thrust against the ______, similar to that of an arch. Outward thrust is resisted by ______________or _______ that are in tension.
Outward.
Walls.
Ceiling or attic floor joists. Collar beams (ties opposing joists together)
If the architect desires to leave the underside of the roof exposed without (ceiling or attic) joists, a __________ must be used to support the rafters.
Structural ridge beam
Rafters commonly made of _______ although _____ and _____ can be found. Wood rafters vary in size from _____ to _______. They can be spaced from ____ to ____ depending on the span and load.
Wood.
Steel and steel truss.
2x4 to 2x14 inches.
12 to 24 inches apart
Truss
Reduced ______ of their components and the ______ of their components make them vulnerable to ____ failure under fire conditions.
Mass
Interdependence
Early
Ceilings are often suspended from roof truss, creating a ________ between the _____ and ____________ and throughout the ______.
Concealed space.
Top and bottom chords.
Ceiling to the roof
______ truss: all of its chords and diagonal members lie in the same plane.
Monoplane
Bowstring trusses - use ______ at all joints except the _______ located at the ends of the truss.
Split-ring connectors.
Heel plates
The _________ trusses are the most common types used for pitch roofs.
Fink and Pratt-style
only mention of trusses and pitched roofs in Ch. 11
Arches.
Laminated wood arches will behave much like _________ and steel truss arches will react to a fire in a manner similar to a _________.
Laminated beams
Steel truss
Lightweight wood trusses: connected using ______, individual members would be wooden _____ or _____ and individual trusses would be spaced _______ apart center to center.
Gang nail-type gusset plates.
2x4s or 2x6s.
2 to 4 feet
There is one characteristic of some arch-supported roofs that can cause a catastrophic failure under fire or conditions and that is the failure of the ___________.
Steel tie rod
between two ends of arch, extends through the building and usually unprotected
The components of roof decks include _____, ______, and ______.
Sheathing.
Roof planks or slabs.
Purlins
The roof deck serves as the roof support
Concrete deck roofs
Roof deck materials for wood panel decking and wood planks.
Dimensions?
Wood panel = thickness 1/2 in., supports 24 in. on center.
Wood planks = minimum 1 in. nominal thickness
Roof deck materials for corrugated steel.
Dimensions?
29 to 12 gauge.
Overall depth of 3/4 to 2 in.
Corrugated with flat steel welded to bottom = Cellar Decking
Which two roof deck materials are nailable and which one needs nailing strips?
Nailable - gypsum and precast (appropriate aggregate).
Cast-in-place (provision made, strips at intervals of 3 ft).
-besides strips, drilled/anchored and placed between rigid insulation panels
The roof covering and the deck are the same
Corrugated steel decking
Multistory building to have flat roof, usual practice is to use:
Same structural system for roof and floors
*exceptions = add’l story to older bldg OR fire damage
General.
Type of roof covering used depends on: (FSCA)
FORM of roof structure.
SLOPE of roof.
Local CLIMATE.
APPEARANCE desired
Because flat roofs ________ than pitched roofs, they usually require more complex roof coverings.
Drain more slowly
Flat roof usually consists of several component layers: (VTMDW)
Vapor barrier. Thermal insulation. roofing Membrane. Drainage layer. Wear course.
WaterTIGHT material to prevent passage of moisture/water vapor.
Reduce the diffusion of interior moisture.
Needed outdoor temp below 40F and indoor relative temp 45% or greater at 58F.
Consists of sheet of plastic, aluminum foil, Kraft paper w/asphalt, asphalt felt
Vapor Barrier
Reduces heat loss through roof.
Resistance to mechanical DAMAGE.
Poured or rigid
Thermal insulation
WaterPROOF material that keeps out rain and snow.
3 general categories: built-up, single-ply and fluid-applied
roofing Membrane
Membrane Roofing =
Overlapping layers of felt saturated with bituminous material (tar/asphalt).
Cemented together with hot bituminous roofing cement.
Felt 3 ft wide/4 layers common.
More felt, more durable
Will last 20 yrs
Built-Up membrane
Membrane Roofing = Single membrane laid in sheets. Sheets 10 or 20 feet wide. Up to 200 feet long. .03-.10 inches thick. Most common material EPDM (PVC and CPE) Accommodate shifting Attached - adhesives, gravel blast, mechanical fasteners
Single-ply
Membrane Roofing =
Useful for bldgs with curved roof surfaces (domes).
Applied as liquid and allowed to cure.
Several coatings.
Neoprene, silicone, polyurethane, butyl rubber
Fluid-applied
Permits free movement of rain water to roof drains.
Can be ballast layer in single-ply, a drainage fabric or aggregate used in built-up roofing
Drainage layer
Protects roof from mechanical ABRASION.
Can consist of aggregate in built-up or gravel ballast.
Built-up that use gravel commonly known as “tar and gravel”.
Gravel surface is used for this, increases resistance of roof to ignition from flaming brands.
May also consist of pavers if roof used for pedestrian traffic
Wear course
Two broad categories of coverings for pitched roofs
Shingle or tile.
Metal.
(Technically, thatch is a covering for pitched roofs)
____ are small overlapping units, with their size allowing for movement between individual units caused by thermal expansion and shifting of the building structural system.
Shingles and tiles
Difference between wood shingles and shakes is in their ________. ______ are thin, tapered slabs of wood that are sawn from pieces of tree trunk. _______ are split by hand or machine and thicker than ______.
Method of production.
Wood shingles.
Shakes, Shingles
Common size for asphalt shingles
12 X 36 in.
Hard rock that has tendency to split along one plane.
Produced in smooth sheets as thin as 1/16 in. up to 1 1/2 in.
Life expectancy of 150 years.
8-36 lbs per sq. ft. so framing/decking heavier than normal
Slate
Ancient material, used for thousands of years.
Shaping in molds and firing in kilns.
Dense, hard and nonabsorbent.
Used for flat or curved, curved known as mission
-imitation or genuine Spanish-style
Clay tile
Portland cement, aggregate and water.
Made to look like clay tile, slate or wood.
Major advantage over wood is greater longevity
Concrete tiles
Installed in an overlapping manner.
-only 1/3 actually exposed to weather.
Nailed to conventional deck or open deck.
-open deck-earlier failure when fire in attic
Wood shingles
Installed over underlayment
- layer of roofing felt/synthetic covering
- serves as cushion and provides protection from wind-driven rain
Asphalt shingles
Prepunched nail holes
-head of nail just touching so it is actually just hanging from the nail
Slate tiles
Advantage - rustic appearance and resistant to wind damage.
Disadvantage - they pose a serious fire potential
-can be easily ignited by burning brands
-once ignited, they produce embers
Can be pressure-impregnated w/fire retardant solution.
Treatment remains effective after exposure to elements.
Painting can reduce effect of fire retardant
Wood shingles and shakes
Fundamentally combustible.
Characteristic heavy black smoke.
Typically produced with grit surface to reduce ease of ignition
Asphalt shingles
__________ can be blown under tiles, such as _______ that don’t lie flat.
Flying brands.
Spanish tiles
Clay, slate, cement tiles.
Fires under the tiles can produce some operational problems: (3)
Tiles become loose and FALL from roof.
Surface becomes SLIPPERY, posing serious fall hazard.
Thin pieces of slate are brittle/SHARP edges, creating a hazard for FF below
Some roof coverings, such as wood and asphalt shingles, are also used for _________. When used for siding, they can become subject to the _________________.
Siding
Heat of an exposing fire
Metal roof coverings make use of several materials including: (6)
Galvanized iron or steel. Copper. Zinc. Aluminum. Lead
Corrugated sheets of aluminum or steel are widely used on:
Industrial and agricultural buildings
Also found on many residential and community bldgs
Corrugated roofing sheets are generally strong enough to be installed ____________. In these cases, the roofing sheets are supported by ______ or ______.
Without decking.
Roof beams or purlins
The spacing between purlins is:
2 to 6 feet
Flat roof sheets are nailed ________.
To a deck beneath
_________ is placed on the deck beneath the metal sheets.
A layer of roofing felt.
Also used as insulation for wood decking (increases fire resistance)
One problem with metal roofing is potential for ________ when __________. To prevent this interaction, nails made of _______ are used.
Galvanic action.
Dissimilar metals are in contact.
The same metal
The individual flat sheets of metal roofing are joined _________. The seams ___________ at the joint between adjacent sheets and make the panel roof ___________.
At the seams.
Stand up vertically.
Readily identifiable
NFPA 256 Roof Coverings-simulates fire exposure conditions for fires ___________ a building. Does not evaluate the fire resistance of the _______________ or the fire resistance of the roof itself with respect to _____________.
Outside a building.
Structural system supporting a roof.
A fire originating WITHIN the building
In the test, samples of roof coverings are attached to _________________.
A wooden deck measuring 3 ft. 4 in. by 4 ft. 4 in.
Six separate tests for NFPA 256
INTERMITTENT flame. SPREAD of flame. BURNING brand. FLYING brand. RAIN. WEATHERING
NFPA 256 test can be repeated from _______ on different samples.
2 to 15 times
Roof coverings that pass NFPA 256 are classified as: (3)
Class A - effective against Severe fire exposure.
Class B - effective against Moderate fire exposure.
Class C - effective against Light fire exposure.
bldgs may or may not have to meet classes depending on constr. type and location
A _________ is a second roof constructed over the original roof. Roof becomes deteriorated so it can not be easily repaired.
Rain roof
Rain roof presents some special difficulties for the firefighter:
Void created between roofs, and any CONCEALED SPACES creates problems.
Fire can travel undetected and is exceptionally HARD TO ACCESS and extinguish.
Can also IMPEDE rapid and effective ventilation.
One manifestation of the interest in environmental protection has been the development of ________.
Green roofs
_____ involves the use of the roof surface of a bldg for a rooftop garden. Several benefits: (2)
Green roof.
One is increased INSULATING effects between bldg interior and outside.
Greatest benefit is increase in AIR QUALITY.
Several forms of green roof (2)
Use of plotted plants and flower boxes.
Layer of earth with growing plants covering large area of roof.
developed on existing roofs AND in new construction
Rooftop garden (not green roof) constitutes a _____ load. The layer of earth can can vary from ____ to ______.
Dead.
Few inches to 1 or 2 feet
(Green roof) Dead load can vary from _____ to ______.
20-150 lbs per sq ft.
(Green roof) In new construction, engineer can _______ but if planned for an existing roof, the __________ must be analyzed.
Provide for this load.
Existing structural system
(Green roof) Under fire conditions, the increased load can _______ but green roof can also ____ and _____.
Hasten structural failure.
Interfere with ventilation.
Fire location indicators.
Photovoltaic cells in panels can be:
Laid on top of a roof OR
Imbedded in the roof
Although solar energy represents clean source of energy, the electricity generated by the operation of the solar system represents a __________.
SIGNIFICANT hazard for firefighters
Hazards for photovoltaic/solar: (3)
Even if shutoff, retain significant amount of electricity.
Not safe to break cells or skylights that are solar powered.
Panels represent a significant tripping and falling hazard
(Photovoltaic) These ALWAYS represent serious safety considerations
Electrical shock.
Inhalation exposure.
Falls from roof.
Roof collapse.
Air-supported roof structures
Typical use would be a _________ and some industries also use these as _______.
Sports practice facility.
Storage facilities
Air-supported roofs _______ lend themselves to conventional firefighting tactics. Attempting to ventilate the roof may result in ___________.
Do NOT.
Loss of interior supporting pressure
Having doors open to provide firefighting access for lengthy periods could result in ______.
Slow deflation of structure
Structure of roof frequently penetrated for number of reasons: (4)
Penthouse.
Skylight.
Vents.
Roof hatches
______ are small structures erected on the main roof of the bldg, in some parts of US referred to as _________.
contains water tanks and/or heating and cooling equipment
Penthouses.
“Bulkhead”
Penthouses has several purposes: (4)
Stairway enclosure.
Elevator machinery enclosure.
Mechanical equipment storage.
Additional living space
A stairwell penthouse can provide a means of ________ and also may _______ from an architectural standpoint.
Unauthorized access.
Not be desirable
Some penthouses may ____________and must be accessed ___________. This is frequently the case it’s penthouses built for ____________.
NOT be accessible from the inside of a building.
From the roof.
Elevator and mechanical equipment
When roof is beyond reach of ladder, firefighters ____________. Although some means of access ________ be provided for maintenance, access may _________ and may entail ___________.
Must locate a route to the roof
Must ALWAYS.
Not be readily apparent.
Climbing up ladders through roof hatches
______ provide natural lighting to the interior of a building and can be located to serve only _________ or they may be located _____________.
Skylights.
The top story of a building.
Over the top of an atrium, stairwell or light shaft
For safety purposes, building codes require ______ or _____ in skylights.
Wired glass.
Tempered glass
Skylights provide a ____________ but they usually do NOT have a ___________.
Rapid means of ventilating heat and smoke.
Provision for automatic venting
Warehouse and industrial buildings are usually built __________ where as office or residential buildings will have ____________.
Without ceilings.
Ceilings installed for esthetic effect
Ceilings as a distinct building component ______ play a STRUCTURAL role however, they ______ have a FUNCTIONAL role in the design of a building.
Usually DO NOT.
CAN
Ceilings can be designed to _________ and _________ in a room.
Control the diffusion of light.
Distribution of air
The _________ created in a fire-resistive or noncombustible construction may _________ above.
Concealed space.
Conceal the type of roof structure
