This document discusses different types of roofs and roof construction. It describes major roof styles like flat, pitched, curved, and domed roofs. Key components of roofs are identified, including the roof deck, support systems, and various covering materials. Roof construction plays an important role in firefighting, as roofs can become unstable or make fire spread difficult to detect during a fire. Firefighters must understand roof architecture and be aware of potential hazards during a structural fire.

1. Building Construction Related to
the Fire Service
Fourth Edition
Chapter 11 — Roofs

2. ‣ Explain the role roofs play in structural
fire fighting.
Learning Objective 1

3. A roof is a waterproof covering for a
building.

4. Roofs play an important role in
structural fire fighting.

5. Firefighters must be familiar with all
aspects of roof construction.

6. Roofs can become overloaded over time if air
conditioning units or other equipment is added.

7. Roofs may make it difficult for firefighters to
determine the extent of a fire or to perform
ventilation.

8. ‣ Describe major architectural styles of
roofs.
Learning Objective 2

9. The roofs of buildings can be classified
from a fire fighting standpoint.

10. Flat roofs are found on all types of
buildings.

11. Many flat roofs are provided with a slight slope,
typically from front to rear, to facilitate drainage.

12. Flat roofs are the easiest roofs which
firefighters can work.

13. A pitched roof is designed to shed
water and snow.
Courtesy
of
Chris
E.
Michal,
NOFD
Photo
Unit

14. Inclined surfaces of pitched roofs may be
categorized into low slope roofs and medium to
high slope roofs.

15. Inclined surfaces of pitched roofs may be
categorized into low slope roofs and medium to
high slope roofs.
Courtesy
of
McKinney
(TX)
FD

16. Inclined surfaces of pitched roofs may be
categorized into low slope roofs and medium to
high slope roofs.

17. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

18. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

19. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

20. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

21. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

22. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

23. Climate, function, and aesthetic considerations
determine the design of pitched roofs.

24. NOTE
‣ Modern ventilation and lighting
systems have largely eliminated the
need for monitor and sawtooth roofs.

25. Curved roofs take their form from the structural
system used to support them, usually arches and
bowstring trusses.

26. More architecturally spectacular curved roofs can
be created using “lamella” arches or geodesic
domes.

27. Lamellas are most commonly made
of wood.

28. Curvature results from the beveling (inclining) of
the ends of the individual lamellas.

29. A geodesic dome can create a nearly spherical
surface by using spherical triangulation.

30. A dormer may be provided in buildings with
pitched roofs to increase the available living
space in an attic.

31. False dormers may be used as
decorative elements.

32. ‣ Identify types of roof support systems.
Learning Objective 3

33. As a tactical factor, firefighters must be able to
identify the type of supports and materials used
in roof construction.

34. Flat roofs may be supported by open-
web steel joists and steel beams.

35. The simplest system of flat roof support uses
ordinary wood joists supported at either end by
load-bearing walls.

36. A traditional wood-joisted roof uses solid wood
joists which tend to lose strength gradually as
they burn.

37. WARNING
‣ Roof support systems can fail without
warning under fire conditions.

38. Box beams and I-beams manufactured from
plywood and wood truss joists are often used to
support flat roofs.

39. CAUTION
‣ Unprotected lightweight open-web
joists of any material should be
expected to fail quickly in a fire.

40. Building codes may allow the omission of
structural fire proofing from roof supports in
Type I construction.

41. Roofs are designed for lighter live
loads than floors.

42. An inverted roof is a variation of a flat roof that
from the outside looks like any other flat roof.

43. Conventionally framed roofs use inclined
members to support pitched roofs built on site.

44. Conventionally framed roofs are becoming less
common than prefabricated framing systems.

45. Conventional framing requires
multiple components.

46. Several types of roof systems are
conventionally framed.

47. The basic design of a raftered roof results
in an outward thrust against the walls.
Courtesy
of
Wil
Dane

48. If ceiling or attic floor joists are damaged or
destroyed in a fire, the roof can push out against
the walls.

49. Conventional roof framing is constructed
using substantial materials.

50. Rafters are commonly made of wood, but steel
beams/trusses can be found in modern
commercial construction.

51. Pre-engineered roof framing, also known as roof
trusses, are a common roof support system.
Courtesy
of
Ed
Prendergast

52. Several types of roof trusses may be
used to support roofs.
Courtesy
of
McKinney
(TX)
FD

53. The joints used in light-weight wood trusses
often are connected using gang-nail type gusset
plates.

54. Void spaces in truss roof construction
are large.

55. Bowstring trusses use a curved top
chord.

56. Bowstring trusses use split-ring connectors at all
joints, except the heel plates located at the ends
of the truss.

57. The failure of any single element of a bowstring
truss will lead to catastrophic failure.

58. Roof trusses may be fabricated from
both steel and wood.

59. Arches will often behave true to their
construction materials in fire conditions.

60. A steel tie rod may be used between the two ends
of the arc in an arch-supported roof to resist
outward thrust.

61. ‣ Describe the function of roof decks.
‣ Identify materials used to construct
roof decks.
Learning Objectives 4-5

62. Roof decks separate the structure from the
effects of weather and support the weight of
weatherproofing materials.

63. The deck of a roof is the portion of roof
construction to which the roof covering or roll
roofing material is applied.

64. Sometimes the roof deck serves as
the roof support.
Courtesy
of
McKinney
(TX)
FD

65. The roof deck material should be clean and
smooth so that any insulation or roof covering
can be attached.

66. Each type of roof deck material is
used in different thicknesses.

67. Some types of roof deck material are
nailable.

68. Cast-in-place concrete decks are not
nailable.

69. In a multistory building with a flat roof the same
structural system is usually used for the roof and
floors.

70. ‣ Distinguish among types of roof
coverings.
Learning Objective 6

71. The roof covering provides a water-
resistant barrier for the roof system.

72. A large number of roof covering
materials and systems are in use.

73. NOTE
‣ Adding layers to roofs should not be
confused with the construction of a
rain roof over an existing roof. Rain
roofs are discussed later in this
chapter.

74. Flat roofs drain more slowly and usually require
more complex roof covering assemblies than
pitched roofs.

75. The vapor barrier is designed to reduce the
diffusion of interior moisture into the insulation
layer.

76. Thermal insulation reduces heat loss
through the roof.

77. Insulation can be poured or rigid.

78. Roofing membrane consists of waterproof
material that keeps rain and snow from the
building’s interior.

79. Built-up membranes use several overlapping
layers of roofing felt saturated with a bituminous
material.

80. A single-ply membrane roof consists of a single
membrane laid in sheets on the roof deck.

81. A single-ply membrane is made from
several types of material.

82. A single-ply membrane can be stretched and
consequently will accommodate shifting in a
building.

83. Application of a single-ply membrane
may result in a fire.

84. Fluid-applied membranes are useful for
buildings with curved roof surfaces.

85. The drainage layer permits the free
movement of rain water to the roof drains.

86. The wear course protects the roof
from mechanical abrasion.

87. Pitched roof coverings function
differently from those used on flat roofs.

88. NOTE
‣ Thatch, which consists of bundles of
reeds, grasses, or leaves, technically is
also a covering for pitched roofs. In
North America, its use is limited to a
few special situations such as for
decorative effect.

89. Shingles and tiles are small, overlapping units
which allow for movement between individual
units.
Courtesy
of
McKinney
(TX)
FD

90. Asphalt shingles are usually installed over an
underlayment, which is a layer of roofing felt or
synthetic covering.

91. NOTE
‣ Slate tiles have preset nail holes. The
proper installation technique is to have
the head of the nail just touching the
slate so that the slate hangs from the
nail.

92. Modern asphalt shingles are
fiberglass based.
Courtesy
of
McKinney
(TX)
FD

93. Asphalt shingles are fundamentally
combustible.

94. Some roof coverings, such as wood and asphalt
shingles, are used for siding as well as for roofs.

95. The difference between wood shingles and
shakes is in their method of production.

96. Wood shingles and shakes used in North
America are made of wood resistant to decay.

97. Shingles and tiles are usually attached to
the roof with corrosion-resistant nails.

98. Wood shingles and shakes can be pressure-
impregnated with a fire-retardant solution.

99. Fire-retardant shingles and shakes are shipped to
the job site with paper labels identifying them.

100. Wood shingles and shakes pose a
serious fire potential.

101. Clay, slate, and cement tiles are noncombustible
and produce fire-resistant roof coverings.

102. Flying brands can be blown under tiles
that do not lie flat and ignite the roof deck.

103. Slate is produced from hard rock that
has a tendency to split along one plane.
Courtesy
of
McKinney
(TX)
FD

104. Clay tile is a dense, hard, nonabsorbent material
that can be used for flat or curved tiles.

105. Concrete tiles are made from portland
cement, aggregate, and water.

106. Metal roof coverings may be used as
corrugated or flat sheets.
Courtesy
of
Ed
Prendergast

107. Metal roofs are found on many
residential and commercial buildings.

108. NOTE
‣ Galvanic corrosion occurs when some
types of dissimilar metals are in
contact. Construction practices to
avoid that corrosion may include using
nails of the same metal as the
sheeting, or using insulation between
the nails and the sheeting.

109. Corrugated roofing sheets are generally stiff
enough to be installed without decking.
Courtesy
of
McKinney
(TX)
FD

110. Metal panel roofs may be readily
identifiable.
Courtesy
of
Sturzenbecker
Construction
Company,
Inc.

111. CAUTION
‣ Visible roofing materials may not
indicate the structural supports
underneath.

112. Fire ratings of roof coverings can be evaluated
by test procedures contained in NFPA® 256.

113. In the test, samples of roof coverings are attached
to a wooden deck measuring 3 feet x 4 feet 4
inches (1 m x 1.3 m).

114. Test procedures may be repeated from
two to fifteen times on different samples.

115. Roof coverings that pass the required
test procedures are classified A, B, or C.

116. Building codes use classifications to
control the flammability of roofs.

117. A rain roof may be installed over an
existing roof.

118. Rain roofs can be constructed of any material
over any material, and can take any shape.

119. A rain roof presents some special
difficulties for firefighters.

120. ‣ Identify types of green design roofs.
Learning Objective 7

121. Green design roofs increase the
energy efficiency of a building.

122. Green design roofs are significantly
heavier than other roofs.

123. A photovoltaic (PV) system (solar)
produces reliable, clean energy.

124. CAUTION
‣ Firefighters may find rooftop
photovoltaic applications on many
structures, regardless of the
occupancy, roof type, or pitch.

125. Photovoltaic cells are typically
shaped as panels and shingles.
Courtesy
of
McKinney
(TX)
FD

126. Photovoltaic systems have increased in
prevalence in residential applications.

127. Photovoltaic systems should be handled with
the same care as any other electrical system.

128. Cells may not be readily identifiable on flat roofs, in
low light, adverse weather, or during fireground
operations.
Courtesy
of
McKinney
(TX)
FD

129. As firefighters pause operations to assess PV
elements, the fire continues to spread and
develop.

130. Codes and other authorities continue to propose
and add parameters regarding photovoltaic
applications.

131. Vegetative roof systems (green
roofs) can take several forms.
Courtesy
of
Ed
Prendergast

132. Rooftop gardens can be developed on
existing roofs and in new construction.

133. A rooftop garden constitutes a dead
load on the roof structural system.

134. Another primary hazard of vegetative
roofs is the added fire load.

135. ‣ Recognize how roof openings can be
used in fire fighting operations.
Learning Objective 8

136. A roof may be built with openings or
with breaches in its continuity.

137. Penthouses are small structures
erected on the main roof of a building.
Courtesy
of
McKinney
(TX)
FD

138. Firefighters can gain rapid access to a roof from
inside a building when a stairwell is present.

139. The primary purpose of skylights is to provide
natural lighting to the interior of a building.
Courtesy
of
McKinney
(TX)
FD

140. Building codes restrict the materials used in
skylights to plastic, wired glass, or tempered
glass.
Courtesy
of
McKinney
(TX)
FD

141. Skylights usually do not have provisions for
automatic venting but most can be opened to
ventilate heat and smoke.

142. CAUTION
‣ Skylights that also serve as smoke and
heat ventilation openings use a fusible
link and may open with great force
and without warning under fire
conditions.