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