Construction Materials and Engineering Diploma (Polytechnics)

1. Construction Materials
and Engineering
Module - IV
Shamjith Km
shamjithkeyem@gmail.com
Department of Civil Engineering
Government Polytechnic College Manjeri

3. Basic building components
Sub structure Super structure
1.Foundation 1. Plinth
2. Beams
3. Columns
4. Walls
5. Arches
6. Roofs
7. Slab
8. Lintel
9. Parapet
10. Staircase
11. Chajjas
12. Lift/ramp
13. Doors
14. Windows
15. Sunshade
16. Ventilator
17. Plinth beam
18. Chimney
Portion of building located
below ground level
Portion of building located
above ground level

4. Foundation1
Transmit load from superstructure to subsoil
For uniform distribution of load
To provide level surface for construction of superstructure
To reduce load intensity
To assure settlements are within permissible limits
To assure soil does not fail in shear
To prevent side wise movements
Most important part of a building

6. Plinth2
Structure between ground and floor
Prevents entry of rain water in to the building
Prevents entry of animals and insects
Generally, Plinth height = 45, 60, 90, 120 cm
Plinth should not be less than 45 cm
Transmit load of super structure to foundation
Plinth provide a level surface
Plinth supports walls

7. Beams3
Horizontal structural element
Takes loads from slabs and transfer to column beneath
Usually beams are made of RCC and steel
Takes vertical loads, shear forces and bending moments
Slabs are provided above beams
Beams are supported on either walls or columns

8. Column4
Vertical structural element
Takes loads from beams and transfer to foundation
Usually columns are made of RCC and steel
Takes compressive loads
Long columns fails by buckling
Short columns fails by crushing

9. Arches5
Normally a curved member with wedge shaped blocks
Carry weight of structure above the openings
Used in buildings, bridges, etc
Usually made of concrete, bricks, or stones

10. Walls6
Building blocks of bricks or stones
Load bearing walls supports slab weight
In framed buildings, acts as partition walls
Provides privacy and protection from heat, cold, dust, noise
Divides the building space to useful rooms
Walls support roof
Gives a structural looking for building
Provides shelter

11. Roof7
Uppermost (slab) portion of a building
Provides privacy and protection
Provides aesthetics to the building
Usually made of RCC, wood, tiles, steel, asbestos, etc
Protects the building from direct rain and heat
May be flat, arch, curved or slopped in shape

12. Floor8
To provide level walking surface
Provides neatness to building
Flooring is done above plinth level/slabs
Provides privacy and protection from heat, cold, dust, noise
To provide useful area for working/placing equipments

13. Doors9
To provide access to various areas in a building
Provides entry and exit system to rooms
Protection from theft and robbery
Usually made of wood, steel, fabrication works, etc
Provides privacy and shelter
Can be made in different shapes and sizes - aesthetics

14. Windows10
To get proper ventialation
Provides fresh air and light inside the room
Protection from theft and robbery
Usually made of wood, steel, fabrication works, etc
Provides privacy and shelter
Can be made in different shapes and sizes - aesthetics

15. Sunshade11
It is a type of cantilever slab
It extends from walls
It protects from rain water
It controls amount of direct sunlight through windows
It is constructed above lintel

16. Openings12
Provides entry and exit without doors
Ventilation and light
Plinth beam13
Beam or belt covering provided above plinth level
To prevent entry of water (dampness)
To provide additional support for load transferring & walls

17. Lintel14
Horizontal structural member
Transfers load above doors & windows to beneath
Usually made of RCC or steel
Width of lintel = width of wall
Provided above doors and windows

18. Staircase/lift/ramp15
Safe access from one floor to another
Support for movement between floors
Usually made of RCC or steel
Suitable provision to escape in case of fire
For vertical transportation

19. Chejjas (Eaves)16
Overhanging cover for windows and doors
Protects from rain water
Provide aesthetics to building
Protects from external sunlight

20. Parapet17
Low protective wall along the edge of a roof,
bridge, or balcony.
Made above flat roofs
It act as a protective edge from falling
Parapet

21. Foundations
Transmit load from superstructure to subsoil
For uniform distribution of load
To provide level surface for construction of superstructure
To reduce load intensity

22. Foundations
Shallow Deep
1. Isolated spread footing
2. Wall/Strip footing
3. Combined footing
4. Cantilever/Strap footing
5. Mat/raft footing
1. Pile foundation
2. Well/Caisson foundation
3. Pier foundation
Shallow depth
Depth ≤ Width
Depth is high
Depth > Width
Weak soils

23. 1. Isolated spread footing
Most common and economical type
Generally used for ordinary buildings
Have independent footings
Each column has its own footings
Footing may be rectangular,
square or circular in shape

24. Isolated footings may be of three types:

25. 2. Wall/Strip footing
Each strip contains number of footings
Helps to distribute loads from columns to ground
Strip will be along direction of wall
A group of columns share single lengthier footing

27. 3. Combined footing
Footings made common to more than one column
Uniform distribution of loads
Opted when columns are closely spaced
Opted when dimensions of one side is restricted

29. 4. Cantilever/Strap footing
Nearby footings connected using a strap/beam
When edge of footing cannot extend beyond property line

31. 5. Mat/raft footing
Used when bearing capacity of soil is poor
Load from number of columns is distributed by
a single large footing called mat.

32. Raft behave as a single unit
Used for heavy construction
works in low load bearing soil

33. 1. Pile foundation
Used when bearing capacity of soil is poor
Pile is a slender (long) member with a small CSA
Used to transmit foundation loads to a deeper rock strata
Pile transmits load either by skin friction or bearing
Used to resist uplift and provide stability against lateral
and overturning forces.

36. 2. Well/Caisson foundation
Provided below water level for bridges
Caisson means ‘box’
Construction of structures in water
Dams, bridges, etc

38. 3. Pier foundation
Used when heavy load is transferred to the ground

39. Flooring
Permanent covering given to a floor
Provides walking surface
Materials: Wood, stone, ceramic, terrazzo, etc

40. Requirements of a good floor
1. Good appearance
2. Can be easily and effectively cleaned
3. Should provide comfort on using – less noise
4. Cost should be reasonable
5. Should have sufficient damp resistance
6. Should be strong and durable
7. Should be fire resistant
8. Should have sufficient hardness
9. Should have minimum maintenance
10.Should be smooth, but don't slipper.

41. Materials used for flooring
Cement or lime concrete
Bricks/tiles
Marble
Glass
Ceramic
Plastic
Mud and murram
Wood
Cork
Linoleum
Flagstones
Asphalt
Rubber

42. Doors and windows
Primarily for air circulation, privacy and light
Made of wood, concrete, steel, aluminum, etc
Door is a movable barrier secured in a wall opening
Designation of doors and windows
10 DS 20
Module width Single Shutter
door
Module height
Note:
1 module = 100 mm

43. Location of door in a building
Preferably at corners of a room (20 cm from corner)
If two doors in a room, face them each other
Number of doors should be kept as minimum
Place such that we get maximum ventilation and wind
Depends on size of room, climatic conditions, utility
and architectural point of view.
Place such that we get
maximum light

44. Height of door = Width + (1 m to 1.2 m)
Eg:- H = 1 m + 1.0 = 2.0 m
H = 1 m + 1.2 = 2.2 m
Width of door = (0.4 to 0.6) x height
Thumb rules for height and width
Eg:- W = 0.4 x 2.0 = 0.80 m
W = 0.6 x 2.0 = 1.20 m
(Residential buildings)

45. Location of window in a building
Place such that we get maximum ventilation and wind
Depends on size of room, climatic conditions, utility
and architectural point of view.
For 30 m3 inside volume  Provide 1 m2 window area
Breadth of window =
1
8
x [width of room + height of room]
15 % of floor area = area of window opening
10 % of floor area = Glass panel area

46. Technical terms
1. Head – top most horizontal part
2. Sill – lower most horizontal part
3. Post
4. Mullion – vertical sub divide
5. Transom – horizontal sub divide
6. Horn – horizontal projections of frame
7. Holdfast
8. Style – vertical outside member of shutter
9. Jamb – vertical surface of an opening
10.Reveal – exposed vertical surface of an opening
11.Rebate – rectangular recess around frame to receive door
12.Stop – block of wood fixed on backside of a door
13.Architrave – mouldings around door or window frame
14.Ground – additional wooden supports to architrave

48. Jamp – Vertical surface of door opening

49. Reveal – exposed vertical surface of an opening

50. Shutter

51. Types of doors
1. Battened and ledged doors
2. Battened, ledged and braced doors
3. Battened, ledged and framed doors
4. Battened, ledged, braced and framed doors
5. Framed and paneled doors
6. Glazed doors
7. Flush doors
8. Louvered doors
9. Revolving doors
10.Sliding doors
11.Swing doors
12.Collapsible doors
13.Rolling shutter doors
14.Wicket gate

52. 1. Battened and ledged doors
Ledge
Batten
Hinge

53. 2. Battened, ledged and braced doors
Ledge
Hinge
Batten

54. 3. Battened, ledged and framed doors
Ledge
Batten
Hinge

55. 4. Battened, ledged, braced and framed doors
Ledge
Batten
Hinge

56. 5. Framed and paneled doors
Top rail
Panel
Mid rail
Style
Bottom rail

57. 6. Glazed doors
Top rail
Glazed Panel
Mid rail
Style
Bottom rail

58. 7. Flush doors Sheets are placed at back and front

59. 8. Louvered (Venition) doors

60. 9. Revolving doors
Used for Queue controlling
Entrance and exit at same time
Suitable for buildings where there is heavy rush of foot traffic

61. 10. Sliding doors

62. 11. Swing doors

63. 12. Collapsible doors
Visibility to both sides is obtained
Ventilation is also obtained

64. 13. Rolling shutter doors
Drum
Rolling shutter
LockHandle
Saves space

65. 14. Wicket gate
Eg: Jail doors
Wicket door

66. Types of windows
1. Fixed windows
2. Sliding windows
3. Pivoted windows
4. Double hung windows
5. Louvered windows
6. Casement windows
7. Metal windows
8. Sash windows
9. Corner windows
10. Bay windows
11. Dormer windows
12. Clerestory windows
13. Lantern windows
14. Gable windows
15. Ventilators
16. Skylights

67. 1. Fixed Windows
fixed to the wall without any closing or opening operation

68. 2. Sliding Windows
window shutters are movable in the frame
Eg: Buses, bank counters, etc

69. 3. Pivoted Windows
Pivots are provided to window frames
Pivot is a shaft which helps to oscillate the shutter
Types
1. Horizontal
2. Vertical

70. 4. Double Hung Windows
Consist of pair of shutters attached to one frame
Shutters are arranged one above the other

71. 5. Louvered Windows
Provided for the ventilation without any outside vision
Eg: bathrooms, toilets and privacy places etc

72. 6. Casement Windows
Widely used and common – Ordinary window
shutters attached to frame and can be opened and
closed like door shutters

73. 7. Metal Windows
Generally mild steel is used
Very cheap and have more strength
Eg: Public buildings

74. 8. Sash Windows
Type of casement window with panels fully glazed
Space between rails is divided into small panels by mean
of small timber members called sash bars or glazing bars

75. 9. Corner Windows
Provided at the corners of room
Light / air can enter room in two different directions

76. 10. Bay Windows
Projected from wall to increase the area of opening
Enables more ventilation and light form outside

77. 11. Dormer windows
Provided for sloped roofs
Enables more ventilation and light
Enhance aesthetic sense of room

78. 12. Clerestory Windows
Provided near roof heights
Provided for room which has greater ceiling height than
the other rooms

79. 13. Lantern Windows
Provided for over the flat roofs
Provided more light & air circulation to the interior rooms

80. 14. Gable Windows
Provided for sloped roof buildings
Provided at the gable end of sloped roof

81. 15. Ventilators
Provided for purpose of ventilation in the room
Provided at greater height than windows nearer
to roof level

82. 16. Skylights
Provided on the top of sloped roofs
To admit more light into the rooms
Provided parallel to the sloping surface
Can be opened when we required

83. Lintel
Horizontal flexural member which bridges gap of the
opening and which permits construction of walls above it.
Width of lintels is usually same as that of wall
Beam provided over an opening for door, window,
cupboard etc., in a wall

84. 1. Wood Lintel
Single/more pieces of wood used
Sometimes strengthened by steel plates at top and
bottom (Flitched beams)

85. 2. Stone lintels
Stones are cut to required width of the wall
Depth of stone piece = 0.1 x Span
Used only for small spans (stone is weak in tension)

86. 3. Brick lintel
For small span openings
Well burnt, good quality bricks used
Curing time: 7-14 days
Needs temporary form work at
time of construction

87. 4. R.C.C. Lintel
For larger spans - form work needed
Provided with suitable reinforcement
Commonly used in building now days

88. 5. RSJ Lintels (Rolled steel joists)
Provided at large openings when loads are heavy
Jointing is done with bolts

89. Sunshade
Cantilever structure constructed to protect building
from direct sunlight and splashing of rain water.
Usually of width 600 mm and 100 mm thickness.
Provides comfort to users
If RCC, monolithic casting with lintel is done
May be constructed with lintel or independently
Designed slope should be provided for easy draingae

90. Sunshade
Monolithic casting Independent casting

91. Canopy and Sun breakers
Structures constructed to control amount of direct
sunlight through building windows.
Heat insulation, shading and protection from raining.
Aesthetic appearance

92. Arches
Structure constructed to
span across an opening
Small wedge-shaped units
joined with mortar 1. Keystone
2. Voussoir
3. Extrados
4. Impost
5. Intrados
6. Rise
7. Clear span
8. Abutment
Supports loads acting above
the openings

93. Arches
Arches transfer loads as inclined loads whereas
lintels transfer loads as vertical loads.
The structure constructed of stones or bricks,
jointed together with mortar.
Used mainly for beautification purposes

95. Technical terms
1 Keystone
Wedge shaped unit at the crown of an arch
2 Voussoir
Wedge shaped units of an arch
3 Extrados (or back)
External curve of an arch
4 Impost
Projection of a pier/abutment

96. Technical terms
5 Intrados
Inner curve of the arch
6 Rise
Vertical distance b/w highest point on intrados &
springing line
7 Clear span
Clear horizontal distance b/w the suports
8 Abutment
End support of an arch

97. Technical terms
9 Piers
Intermediate supports of an arcade
10 Arcade
Arcade means a series of arch
11 Soffit
Inner surface of the arch (same as intrados)
12 Crown
Top point of an arch

98. Technical terms
13 Skewback
Inclined surface of a pier perpendicular to load direction
14 Springing lines
Imaginary lines connecting springing points
15 Springer
First voussoir at springing level on either side of an arch.
It is immediately adjacent to the skewback

99. Technical terms
16 Haunch
Lower half portion of arch b/w crown and skewback
17 Height of arch
Perpendicular distance b/w intrados and extrados
18 Ring
Circular course forming an arch
19 Spandril
Irregular triangular space formed b/w extrados and
horizontal line drawn to the tangent.

101. Types of Arches
Shape No.of centers Workmanship Material
1.Flat arch
2.Segmental
3.Semi-circular
4.Semi-elliptical
5.Inverted
6.Pointed
7.Relieving
8.Horse-shoe
9.Stilted
10.Venetian
11.Florentine
1.One centered
2.Two centered
3.Three centered
4.Four centered
5.Five centered
1.Rough arch
2.Axed/rough cut
3.Gauged
1.Stone arches
2.Brick arches
3.Concrete arches

102. Flat arch1
Apparent shape is flat
Skewback forms an angle of 60o with horizontal

103. Segmental arch2
Common type used in buildings
One centre – below springing line
Skewback – inclined (perpendicular to load)

104. Semi-circular3
Line of action of load - vertical
Skewback - horizontal
Centre of arch = midpoint of springing line

105. Semi-elliptical4
Arch has more than one center (3 or 5)
Shape of semi ellipse
Centre of arch = midpoint of springing line

106. Inverted arch5
To increase bearing power of soil
Placed below foundation
Eg: british bridges

107. Pointed or gothic arch6
Consist of two curves meeting at apex of triangle
Triangle – equilateral or isosceles triangle
Isosceles – Lancet arch

108. Relieving arch7
Constructed over a wooden joist or flat arch

109. Horse-shoe arch8
For architectural considerations
More than a semi-circle
Center above springing line

110. Stilted arch9
Semi-circular shape attached to tops
Springing line passes through tops of
vertical portions.

111. Venetian arch (Tuder arch)10
Depth at crown > depth at springing line
Four centers on springing line

112. Florentine arch11
Florentine arch with semi-circular intrados

113. Vertical Transportation
Four major modes of vertical transportation are:
1.Stairs
2.Escalators
3.Lifts (Elevators)
4.Ramps

114. Staircase and its location
Should provide easy access to all in the building
Check for good lighting and ventilation
Should have convenient approaches and spaces
Stairs should be located near main entrance in
case of a public building.
In residential buildings stair should be placed
centrally.

115. Types of staircase
Straight
stairs
Turning
Stairs
Geometrical
stairs
Circular
stairs
1.Quarter turn
2.Half turn
3.Three quarter turn

116. Straight stairs1
All steps leads in one direction only
May consist of one or more flights
Used when space available
is long, but narrow

117. Turning stairs: Quarter turn stair2.a
Have a turning of one right angle – 90o
Bifurcated stair
If a quarter turn stair is branched
into two flights at a landing

118. Turning stairs: Half turn stair2.b
Have a turning of two right angles – 180o
May be dog legged or open well (newel) type
dog legged stair Open well stair

119. Turning stairs: Three quarter turn2.c
Have a turning of three right angles – 270o
May be dog legged or open well (newel) type

120. Circular / helical / spiral stairs3
Steps radiates from the centre
No intermediate newel posts or any landings
Flight consists of winders only

121. Geometrical stairs4
Of any geometrical shape

122. Cantilever/Jackknife stair5

123. (KPBR, page 54)

124. Standards for stair case as per KBR
If no.of floors > 4 : provide two staircases
(One for fire escape)
Minimum width = 1.2 m
Minimum width of thread = 30 cm
Maximum height of riser = 15 cm
Minimum height of handrail = 90 cm
Minimum = 3 steps, maximum = 12 – in a flight
Reduce use of spiral staircase
No.of risers = Total height of floor/height of riser
No.of treads = no.of risers - 1

126. Technical terms
1 Baluster
Vertical member fixed b/w string and handrail for safety
2 Balustrade (Barrister)
Combined framework of handrail and balusters
3 Flight
Unbroken series of steps b/w landings
4 Going
Horizontal distance b/w faces of two consecutive risers

127. Technical terms
5 Handrail (Guard rail)
Inclined rail over the string for safety.
6 Headroom
Vertical distance b/w tread and overhead obstruction.
Should be > 2 m
If less than 2 m, heads of people hits the obstruction
7 Landing
Horizontal platform b/w two flights which facilitates
change in direction and provide opportunity to take rest.

128. Technical terms
8 Newel post
Vertical member provided at beginning & end of a flight
9 Nosing
Projecting part of tread beyond the face of riser.
10 Pitch
Angle of inclination of stair with floor. Should be <38o
11 Rise
Vertical distance b/w two successive treads

129. Technical terms
12 Riser
Vertical portion of a step that supports the thread.
13 Run
Total length of stair in a horizontal plane (includes landing)
14 Scotia
Additional finish/moulding provided at bottom of nosing

130. Technical terms
15 Soffit
Under surface of a stair
16 Step
A combination of tread and riser
17 String
Inclined member of a stair which supports ends of steps
18 Tread
Horizontal upper portion of a step

131. Technical terms
19 Waist
Thickness of structural slab in case of RCC stair
20 Walking line
Approx. line of movement of people on a stair during
ascent/descent. It is 450 mm from the hand rail from
centre of handrail.

132. A vertical transportation system
Lift
Moves people and goods b/w floors
Electrically operated equipment
If building height exceeds 10 m
or > 3 storeys, provide lift

133. Lift can be provided inside or outside the building
Lift - location
Inside  near staircase or independent to staircase
Outside  with access to the building landing
Need to provide easy access for all building users
Not preferred at corners
Should give provision for future expansions, if any
Provides much comfort to the users

134. Cab/Car
Buffer
Landing level
Trailing cable
Landing door
Counter weight
Machine room
Lift shaft
Lift pit/well

135. 1. Lift car/cab
Lift – Technical terms
Vertically moving cabin in which passengers and
goods are transported.
2. Lift shaft/hoist
space in which the lift cabin moves.
3. Machine room
Room from which the lift functions are loaded and
controlled

136. 4. Lift pit or Lift well
Lift – Technical terms
Specially dug hole into which the lift is "housed"
5. Buffer
Provided in lift pit for safe landing of cab at bottom
6. Counter weight or balance weight
a separately guided mass that partly
counterbalances the cabin and secures ropes
pressure to a driving pulley.

137. 7. Trailing/suspension cable
Cable which holds car and counter-weight
Lift – Technical terms
8. Governor
Controls speed of the lift
9. Passngers
Passenger capacity assumed as 68 kg/person

138. Ramps
When large number of persons/vehicles have to
be moved from floor to floor.
Is a uniformly sloping surface or inclined plane.
Occupy larger space than stairs and lifts
Easy for sick people
to climb on ramps

139. Ramps
Maximum gradient = 1 in 10
Minimum width = 1.2 m
Minimum height of handrail = 80 cm

140. Escalators
Power driven, inclined, continuous stairways used
for transporting passengers in airports, malls, etc
Operate automatically without operators
Provided with moving handrails.

141. Ceiling
Overhead interior surface that covers the upper
limits of a room – provided below roof/slab
Not considered as a structural element

142. To reduce the heat transfer from the roof
Functions of ceiling
To improve appearance
To conceal all ducts, pipes, wiring and light fittings
To reduce volume of the room
Improve its air conditioning
Improve acoustical quality – sound proof

143. Materials used for ceiling
 Wood
 Gypsum board
 Plaster of paris
 Thermocol
 Extruded Aluminium
 Acoustical boards
 Glass mirrors
 Metal Sheets

144. Types of ceilings
Suspended
ceiling
False
ceiling
Ordinary
ceiling
• Also called as drop ceiling
• Consists of panels that
hang a few inches below
the main structural ceiling
• Area above dropped
ceiling is called plenum
space

145. A dropped ceiling or secondary ceiling hung below
the main (structural) ceiling
False ceiling
To conceal all ducts, pipes, wiring and light fittings
Acoustic balance and control in a room
Aesthetic improvement

146. Should be durable and portable
Requirements of good ceiling
Material used should be light in weight - drop
Should be water/sound/fire proof
Should have aesthetic looking after installation
Should possible to install easily
Should have enough strength and integrity
Possible to cast in any shape – flexible in nature

147. Roof
Uppermost part of building which protects building
from snow, rain, sun, etc
Structural elements may be trusses, portals, slabs,
domes, etc

148. Roof

149. Important technical terms
1 Barge board
Wooden boards fixed on gable end of a roof
2 Battens
Thin wooden strips fixed on rafters to support roof ceiling
3 Cleat
Small wooden blocks to prevent sliding of purlins
4 Eaves
Lower edge of slopping surface of a roof

150. Important technical terms
5 Purlin
Wooden pieces placed horizontally on principal rafters
6 Common rafter
Intermediate rafters supporting roof covering
7 Ridge piece
Wooden piece provided at the ridge line of a slopping roof
8 Wall plates
Long wooden members embedded on top of walls to
receive the common rafter.

151. Should be durable – against rain, wind, snow, and sun
Requirements of a good roof
Should provide desirable insulation from heat and sound
Should be structurally stable and sound – take loads
Should be well drained – slope/drainage facilities
Efficient water proofing
Fire resistant
Good appearence

152. Classification of roofs
Pitched
(slopping) roof
Flat (terraced)
roofs
Curved roofs
1. Single roof
2. Double or purlin roof
3. Trussed roofs

153. Pitched (Slopped) Roofs
Used in places where rainfall and snow fall is high
Slope > 10o (may be 45o -60o )
Preferred for large span structures like workshops,
ware houses, factories, etc
1

154. Types of pitched roof
Single roofs Double or
Purlin roofs
Trussed roofs
Span < 5 m
Span > 2.4 m
For higher spans
1. Lean to roofs
2. Couple roofs
3. Couple-close roof
4. Collar beam roof
5. Collar and scissor roof

155. Single roofs
Span < 5m
Commo rafters are provided to each slope without any
intermediate support.
Commo rafters have single span
No purlins
A

156. Lean to roof (Pent/Aisle roof)
Maximum span = 2.40 m
Generally used for sheds, verendas, etc
1

157. Couple roof
Maximum span = 3.60 m
2

158. Couple-close roof
Legs of common rafters connected by a tie beam
3
Maximum span = 4.20 m

159. Collar beam roof
Tie beam raised and placed at a higher level
4
Maximum span = 4.80 m

160. Collar and scissor roof
Two collar beams
5

161. Double or Purlin roofs
Span > 2.4 m
Intermediate supports are introduced (Purlins)
Also called as ‘Rafter and Purlin roof’
B

162. Trussed roofsC
If span is more, a frame work of slender members are used
to support sloping roofs - trusses
A number of trusses may be placed lengthwise to get wall
free longer halls.
For spans up to 9 m wooden trusses may be used but for
larger spans steel trusses are a must.
Carpentry joints, Bolts and straps, rivets or welding are
made to connect various members at a joint
End of trusses are supported on walls or on column

163. 1 King post truss : 5 to 8 m
2 Queen post truss : 8 to 12 m
3 Mansard truss
4 Truncated truss
5 Bel-fast (bow string/latticed) truss : 30 m
6 Steel truss
7 Composite truss
Types of trussed roofs

164. 1 King post truss 2 Queen post truss
3 Mansard truss 4 Truncated truss

165. Flat (terraced) Roofs
Used in plain areas where rainfall is less and
climate is moderate
Nearly flat (Slope < 10o)
2
Treated with water proofing chemicals
Types
1. Madras terrace roof
2. Bengal terrace roof
3. RCC roof

166. Curved roofs
Thin curved surfaces which transfer load by
membrane compression
Caves are having natural shell roofs
3
To cover large column free areas required for
auditoriums, factories, etc.
Domes

167. Roof Coverings for Pitched Roofs
Selection depends upon:
1. Climatic conditions
2. Fabrication facility
3. Availability of materials
4. Affordability of the owner
Types
Thatch Shingle Tiles
Slates AC Sheets GI Sheets
Aluminum sheets PVC sheets

168. Thatch Covering
Thatch is a cheap roof covering of straw, reed, etc
Tied with ropes or twines to the supporting structures.
1
Suitable for small spans residential buildings in villages
Supporting structure consists of round bamboo rafters

169. Shingles
Are split or sawn thin pieces of wood
Commonly used in hilly areas for low cost housing
2
They are nailed to supporting structures
They have very poor fire and termite resistance

170. Tiles
Clay tiles are easily available at lower costs
supported over battens which are in turn supported by
rafters or trusses
3
Can be easily manufactured and placed in position
They give good interlocking and appearance

171. Slates
Grey sedimentary rock that can easily split into thin sheets
A good slate is hard, tough, durable and have rough texture
4
Used in areas where slate quarries are nearby
They do not absorb water
they give ringing bell like sound when struck

172. A.C. Sheets (Asbestos cement)
Consists of 15 per cent of asbestos fibres evenly distributed
and pressed with cement
Fixed to the steel purlins using J-bolts and washers
5
Commonly used as covering materials in ware houses,
godowns or for larger halls

173. G.I. Sheets (Galvanized Iron)
Corrugated sheets fixed to steel purlins using J-bolts
and washers
Galvanization of iron makes them rust proof
6
Durable, fire proof, light in weight and need no
maintenance

174. Aluminum sheets
Aluminum is lighter in weight
Good anti-rust effect
7
Durable, fire proof, and need no maintenance
Resistant to rot and rust, and insects like termites.

175. PVC sheets
Polyvinyl Chloride (PVC) sheets are flexible
Good damp proof
8
Durable and need no maintenance
Not suitable for high temperature regions

176. Comparison of GI and AC Sheets
G.I Sheets A.C Sheets
Sheets are thin Not as thin as G.I sheets
Light in weight Slightly heavier
Do not break while handling Chances of breaking
Chances of corrosion No corrosion
More noisy if something falls Less noisy
Less fire resistant More fire resistant
Less resistance to acids More resistance to acids
Costly Less costly

177. Method of arranging and fixing -
to the battens, rafters and purlins
Principal rafter is part of roof truss
Purlins are placed for required lengths at regular gaps
They are connected using suitable bolts/joints
Common rafters are placed above these purlins
Battens are fixed above these common rafters providing
suitable overlaps.
Sheets should be laid with smooth side upwards.
Hole for fixing should be drilled. Don’t punch/hammer
Sheets should be properly cut to avoid gaps/spaces

178. R.C.C Roofs
Reinforced cement concrete roofs
Concrete takes compressive loads and steel takes tensile
loads coming above the roof.
Roofs are supported over beams/load bearing walls
Can be simply supported or cantilevered
Usually monolithically cast with beams
May be slopped or flat roof

179. Flat slab construction
A flat slab is a reinforced concrete slab supported
directly by concrete columns without the use of beams

180. Types of Flat Slab Construction
1 Simple flat slab
2 Flat slab with drop panels
3 Flat slab with column capital
4 Flat slab with both drop panels
and column capital

181. Simple flat slab Flat slab with
column capital
Flat slab with column
capital and drop panel
Simple flat slab

182. Causes of dampness in roofs
1 Poor quality of construction material
2 Bad design
3 Fault in construction
4 Rain water falling on walls, parapets, etc
5 Inadequate roof slopes
6 Leakage in the building components

183. Weather proof course to flat roof
1 Injection Grouting For Cracks
2 Bitumen coating
3 Screed concreting
4 Epoxy Coal Tar
5 M-Seal
6 Silicon Sealant
By applying any of below techniques, roofs can make
weather/water proof

184. - Concluding the Subject -
Module What we learned
1 Building materials
2 Ornamental materials for finishing
3 Construction technology
4 Building components

185. A good teacher is someone who can
learn from their students, who can
learn with them, and learns for them.
- Thank You -