Building Components - Civil Engineering

Question 1

What is the Substructure?

Answer 1

Substructure is defined as the structural work below ground level used to support the
structure above. Foundations, basement, subfloor are some components of this area.

Question 2

What is Superstructure?

Answer 2

Superstructure is an upward extension of an existing structure above a baseline called Ground Level in general and it usually serves the purpose of the structure’s intended use.
The various members of super-structure such as columns and beams are designed to provide strength for carrying the dead load and live load expected to come on the various parts of the structure in a safe and well distributed manner.

Question 3

What is a foundation? List the requirements.

Answer 3

Foundation is the most important part of the building. Building activity starts with digging the ground for foundation and then building it. It is the lower most part of the building. It transfers the load of the building to the ground.
Its main functions and requirements are:
1. Distribute the load from the structure to soil evenly and safely.
2. To anchor the building to the ground so that under lateral loads building will not
move.
3. It prevents the building from overturning due to lateral forces.
4. It gives level surface for the construction of super structure.

Question 4

Explain the types of foundation.

Answer 4

Types of foundation:
Mainly there are two types of foundation: they are shallow and deep foundation.

Shallow Foundation: If the depth of foundation is less than or equal to width of foundation
is called shallow foundation. EX; Masonry footing, Isolated footing, combined footing, strap
and RCC footing etc

Deep Foundation: If the depth of foundation is greater than the width of foundation is called
Deep foundation. EX. Friction piles, Load bearing piles (End bearing piles), compaction
piles, well foundation, caissons.

Masonry Footing: Masonry footing is comes under stepped footing category. A step footing
is the one which provides a continuous longitudinal bearing. The spread footing for a
continuous wall is called strip footing. When the wall carries heavy load or when the SBC of
soil is not very high, then one can go for stepped masonry footing. According to National
Building Code in Brick and stone masonry slope is 0.5 H: 1V

Isolated Footing: separate footings are provided for each column, it is called isolated
column footing. The size of footing is based on the area required to distribute the load of the
columns safely over the soil . These footings are provided over a 100 to 150 mm bed
concrete. Required reinforcements and thickness of footing are found by the design
engineers. Thickness may be uniform or varying.

Combined Footing: If more than one column is placed on the bottom of the footing is called
combined footing. The shape is generally rectangular, trapezoidal in section. A Combined
footing is so proportioned that the center of gravity of the supporting are is in line with the
center of gravity of the two column loads.

Raft Footing: A raft /matt is a thick reinforced concrete slab, which supports all the loads
bearing wall and columns loads of a structure or a large portion of structure.If the sum of the
base areas of the footings required to support a structure exceeds about half the total
buildings area then it is preferable to combine the footings into a single raft. In raft
foundation uniform settlement is allowed up to 5 cm, but the differential settlement should
not greater then 2 cm. Raft is used when the loads are heavy and soil is very weak or highly
compressible and to avoid differential settlement in erratic soil. Raft is very useful in resisting
large hydraulic uplift.

Pile Foundation: If the depth of foundation is greater, than the width/diameter of the
foundation is called Deep foundation. Following situations Pile foundation is preferred.
1. The load of the super structure is heavy and its distribution is uneven.
2. The top soil has poor bearing capacity.
3. The subsoil water level is high so that pumping out of water from the open trenches
for the shallow foundation is difficult and uneconomical.
4. The structure is situated on sea shore or river bed.
5. The top subsoil is expansive in nature.

Question 5

What are friction Piles and End Bearing Piles?

Answer 5

Friction Piles: Friction piles are used to transfer loads by means of skin friction along the
surface area of the piles. For friction pile, Df>B where Df= Depth of the pile B= Diameter of
the pile. Such piles are used if hard strata are not available to a considerable depth. The
friction developed is to be properly assessed before deciding the length of the pile. The
surface of such piles is made rough to increase the skin friction so that required length of pile
is reduced.

End Bearing Piles: End Bearing Piles are used to transfer load through the pile tip to a
suitable hard bearing stratum passing soft soil or transforming load through water. Df>B
where Df= Depth of the pile, B= Diameter of the pile

Question 6

What are Walls?

Answer 6

Walls are built to partition living area into different parts. They impart privacy and protection
against temperature, rain and theft. Walls may be classified as:
1. Load bearing walls
2. Partition walls.

Question 7

Differentiate between Load Bearing Walls and Partiton Walls.

Answer 7

Load Bearing Walls:
They carry loads from roof, floor, self-weight etc.
They are thick and hence occupy more floor area.
As the material required is more the construction
cost is more
Stones or bricks are used for the construction.

Partition Walls
They carry self-weight only.
These walls are thin and hence occupy less floor
area.
As the material required is less, the construction
cost is less.
Stones are not used for the construction of
partition walls.

Question 8

What is a roof? Mention the types of roofs.

Answer 8

Roof is the upper most portion of the building which protects the building from rain, wind
and sun.

Various types of roofs used may be divided broadly into three types:

1. Flat roofs
2. Pitched roofs
3. Shells and folded plates

Question 9

What are flat roofs? Explain and state the advantages and disadvantages.

Answer 9

Flat Roofs
These roofs are nearly flat. However slight slope (not more than 10°) is given to drain
out the rain water. All types of upper storey floors can serve as flat roofs. Many times top of
these roofs are treated with water proofing materials-like mixing water proofing chemicals in
concrete, providing coba concrete. With advent of reliable water proofing techniques such
roofs are constructed even in areas with heavy rain fall.

The advantages of flat roofs are:

1. The roof can be used as a terrace for playing and celebrating functions.
2. At any latter stage the roof can be converted as a floor by adding another storey.
3. They can suit to any shape of the building.
4. Over-head water tanks and other services can be located easily.
5. They can be made fire proof easily compared to pitched roof.

The disadvantages of flat roofs are:
1. They cannot cover large column free areas.
2. Leakage problem may occur at latter date also due to development of cracks. Once
leakage problem starts, it needs costly treatments.
3. The dead weight of flat roofs is more.
4. In places of snow fall flat roofs are to be avoided to reduce snow load.
5. The initial cost of construction is more.
6. Speed of construction of flat roofs is less

Question 10

What are pitched roofs?

Answer 10

Pitched Roofs
In the areas of heavy rain falls and snow fall sloping roof are used. The slopeof roof
shall be more than 10°. They may have slopes as much as 45° to 60° also. The slopedroofs
are known as pitched roofs. The sloping roofs are preferred in large spanned structures like
workshops, factory buildings and ware houses. In all these roofs covering sheets
likeA.C.sheet, G.I. sheets, tiles, slates etc. are supported on suitable structures. The
pitchedroofs are classified into; Single roofs, Double or purlin roofs and Trussed roofs.

Question 11

What is a single roof?

Answer 11

Single Roof: If the span of roof is less than 5 m the following types of single roofs are used.

1. Lean to roofs
2. Coupled roofs
3. Coupled-close roof
4. Collar beam roof

Question 12

What are Double or Purlin Roofs?

Answer 12

If span exceeds the cost of rafters increase and single roofbecomes
uneconomical. For spans more than 5 m double purlin roofs are preferred. Theintermediate
support is given to rafters by purlins supported over collar beams. Figure 8.14shows a typical
double or purlin roof.

Question 13

What is trussed roof?

Answer 13

Trussed Roof:
If span is more, frame works of slender members are used to support sloping
roofs. These frames are known as trusses. A number of trusses may be placed lengthwise to
get wall free longer halls. Purlins are provided over the trusses which inturn support roof
sheets. For spans up to 9 m wooden trusses may be used but for larger spans steel trusses are
a must. Depending upon the span, trusses of different shapes are used. End of trusses are
supported on walls or on column.

Question 14

What is Shells and Folded Plate Roofs?

Answer 14

Shell roof may be defined as a curved surface, the thickness of which is small compared to the other dimensions. In these roofs lot of load is transferred by membrane compression instead of by bending as in the case of conventional slab and beam constructions

Question 15

What are doors?

Answer 15

The function of a door is to give access to building and to different parts of the building and to deny the access whenever necessary. Number of doors should be minimum possible.
The size of the door should be of such dimension as will facilitate the movement of the largest object likely to use the doors. In case of the residental buildings, the size of the door should not be less than 0.9 m × 2.0 m.larger doors may be provided at main entrance to the building to enhance the aesthetic view. Minimum sized doors are used for bath rooms and water closets. The size recommended is 0.75 m × 1.9 m. As a thumb rule height of door should be 1 m more than its width.

Question 16

List the types of doors.

Answer 16

Battened and Ledged Doors
Framed and Panelled Doors
Flush Doors
Louvered Doors
Revolving Doors
Swing Doors
Sliding Doors
Collapsible Doors

Question 17

Explain any 3 types of doors.

Answer 17

Battened and Ledged Doors: Battens are 100 mm to 150 mm wide and 20 mm thick wooden boards. Their length is that of door opening. The battens are connected by horizontal planks, known as ledges of size 100 to 200 mm wide and 30 mm thick. Usually three ledges are used one at top, one at bottom and the third one at mid-height. This is the simplest form of
door and the cheapest also. Battens are secured by tongued and grooved joint. If doors are wide apart from using battens and ledges diagonal members, known as braces, are provided to
strengthen the door

Framed and Panelled Doors: This type of door consists of vertical members, called styles and horizontal members called rails. The styles and rails are suitably grooved to receive panels. The panels may be of wood, A.C. sheet, glasses etc. The panels may be flat or of raised type to get good appearance. These are very commonly used doors. They may be of
single shutter or of double shutter.

Flush Doors: The shutters of these doors are made of plywood or block boards. They are of uniform thickness. These shutters are available with different attractive vineer finishes. The time consumed in making such doors at site is quite less. These doors are suitable for interior portion of a building.

Louvered Doors: Whenever privacy as well as ventilation is required such doors can be used. Louvers are the glass, wooden or A.C. sheet strips fixed in the frame of shutter such that they prevent vision but permit free passage of air. The doors may be fully or partially louvered. Such doors are commonly used for public bathrooms and latrines.

Revolving Doors: It consists of a centrally placed pivot to which four radiating shutters are attached. The central pivot is supported on ball bearing at the bottom and has a bush bearing at the top. The shutters may be partly or fully made up of glass.

Swing Doors: Swing door has its shutter attached to the frame by means of double action
springs. Hence shutter can move both inward and outward. They may be single shuttered or
double shuttered. Such doors are preferred in offices and banks.

Sliding Doors: In this type of doors, shutter slides on the sides. For this purpose runners and guide rails are provided. Sliding shutters may be one, two or even three.

Collapsible Doors: Steel channels 16 to 20 mm wide are used as verticals. They are placed with 12 to 20 mm gap. Steel flats 16 mm to 20 mm wide and 5 mm thick are hinged to them. The rollers are provided at their top as well as at bottom so that shutter can be pulled or pushed sideways with slight force.

Question 18

What are Rolling Shutters?

Answer 18

Rolling Shutters: Figure 8.30 show a typical rolling shutter door. It consists of a frame, a drum and a shutter made of thin steel plates. The width of the door may vary from 2 to 3 m.
The shutter moves on steel guides provided on sides and can easily roll up. These types of doors are commonly used as additional doors to shops, offices, banks, factory, buildings from
the point of safety.

Question 19

What are windows?

Answer 19

Windows are provided to give light and ventilation. They are located at a height of 0.75 m to0.90 m from the floor level. In hot and humid regions, the window area should be 15 to 20 per cent of the floor area. It is preferable to have at least two openings in two
different walls. Another thumb rule used to determine the size of the window opening is for every 30 m3 inside volume there should be atleast 1 m2 window opening.
Various windows used may be classified on the basis of materials used, types of shutters, types of openings of shutters and the position of windows. Timber, steel and aluminium are commonly used to make window frames. Shutters of windows may be panelled, glazed or louvered. Window shutters may be fixed, centrally pivoted, sliding type or double hung

Question 20

Give the classification of windows.

Answer 20

Casement windows are common type of windows, provided in the outer walls. They
are provided over 50 to 75 mm sill concrete at a height of 750 to 900 mm from floor
level.
1. Bay windows are provided on the projected portion of walls.
2. Corner windows are provided in the corner of a room. They need heavy lintels.
Corner post of window should be strong enough to take load due to deflection of lintel
and impact load from the shutters.
4. Clear storey windows are provided when the height of the room is much more than
adjacentroom/varandah. It is provided between the gap of low height room and the top
of room with greater height.
5. Gable windows are provided in the gable portion of the building. They are required
in the staircases or in the halls with gable walls.
6. Sky light windows are provided on a sloping roof. It projects above the top sloping
surface. The common rafters are to be trimmed suitably.
7. Dormer windows are vertical windows on the sloping roof.

Question 21

What are ventilators?

Answer 21

Ventilators are provided close to roof level or over the door frames. They help in pushing out exhaust air. They may be provided with two split and separated glasses or with hung shutters.

Question 22

What is flooring?

Answer 22

Purpose of flooring is to get a good hard, level and beautiful surface for living. The floors
directly resting on the ground are known as ground floors while the floors of each storey are
known as upper floors.

Question 23

List the types of flooring.

Answer 23

1. Mud and Moorum Flooring
2. Brick Flooring
3. Flag Stone Flooring
4. Cement Concrete Floors
5. Terrazo Flooring
6. Mosaic Flooring
7. Marble/ Granite Flooring
8. Tiled Flooring
9. Timber Flooring
10. Rubber Flooring
11. P.V.C. Flooring

Question 24

Explain any 3 types of flooring.

Answer 24

1. Mud and Moorum Flooring: These floorings are used in low cost housing, specially in villages. Over the hard layer of earth filling mud or moorum layer is provided. The floor needs a thin wash of cow dung at least once a weak.
2. Brick Flooring: This is also a cheap floor construction. It is commonly used in godowns and factories. Bricks are laid flat or on edges. Bricks of good quality should be used for the construction. Brick layer is provided on sand bed or on lean concrete (1 : 8 : 16) bed.
   In both cases joints are rendered flush and finished with cement mortar.
3. Flag Stone Flooring: Laminated sand stones or slates of 20 mm to 40 mm thick in the form of slabs of 300 mm × 300 mm or 450 mm × 450 mm or in the form of rectangles of size 450 mm × 600 mm are used as floor finishes. The stone slabs are laid on 20 to 25 mm
   thick mortar spread over concrete bed. The joints are to be finished with rich mortar.
4. Cement Concrete Floors: It is modestly cheap and durable floor and hence commonly used in residential, commercial and industrial buildings. It consists of two courses basecourse and wearing coat. Base course is laid over well compacted soil. Its thickness is
   usually 75mm to 100 mm. It consists of lean cement concrete mix (1:4:8). After base coarse is hardened wearing coat of 40 mm is laid. It consists of panels of 1 m × 1 m, 2 m × 2 m or 1 m× 2 m. Alternate panels are laid with 1:2:4 concrete using wooden, glass or asbestos strip separators of 1.5 mm to 2.0 mm thickness.
5. Terrazo Flooring: Terrazo finishing coat is applied over concrete flooring to get
   pleasing appearance. Terrazo finish consists of 75 to 80% of surface marble chips embedded
   in cement mortar. Marble chips are mixed in cement in the proportion 1:1.25 to 1:2 and about
   6 mm terrazzo topping is laid. The top is tamped and rolled. Additional marble chips are spread during tamping to get proper distribution of marble chips on the surface. After drying it for 12 to 20hours, it is cured for 2–3 days. Then grinding is made. After each grinding cement grout of cream-like consistency is applied and cured for 6–7 days. After final grinding and
   curing the floor is washed with plenty of water and then with dilute oxalic acid solution. Then floor is finished with polishing using machines and wax polish.
6. Mosaic Flooring: It consists of a finishing coat of small pieces of broken tiles of Chinaglazed or of marble arranged in different patterns set in lime-surkhi or cement mortar.
   The base coarse is concrete flooring and on it 30 to 40 mm mortar layer is provided. On this mortar layer broken pieces of China glazed or marble are set to get different attractive patterns.
   After 20 to 24 hours of drying the top is rubbed with carborundum stone to get smooth and polished surface.
7. Marble/ Granite Flooring: Marble/ Granite slabs are cut to get marble tiles of 20 to 25 mm thickness. They are laid on floors similar to other tiles. With power driven machine surface is polished to get even and shining surface. This type of flooring is widely used in
   hospitals and temples.
8. Tiled Flooring: This is an alternative to terrazo flooring, used commonly used in residential,office and commercial buildings. On the concrete base, 25 mm to30 mm thick mortar is laid and these tiles are placed and pressed with trowel or wooden mallet. Next day
   joints are cleaned of loose mortar and raked up to 5 mm depth. Then that is filled with coloured cement slurry to get uniform colour on the top surface. After curing for 7 days grinding and polishing is made as in the case of terrazo flooring.
9. Timber Flooring: Timber flooring are used in dancing halls and in auditoriums. Timber plates may be directly placed on concrete bed or may be provided over timber frame work. In latter case it is necessary to provide proper ventilation below the floor. This flooring
   is costly.
10. Rubber Flooring: Tiles or sheets of rubber with fillers such as cotton fibres, asbestos fibre or granulated cork are manufactured in variety of patterns and colours. These sheets or tiles may be fixed to concrete or timber floors. These floors are attractive and noise proof. However they are costly.
11. P.V.C. Flooring: Poly-Vinyl-Chloride (PVC) is a plastic which is available in different colour and shade. Nowadays tiles of this material are used widely. Adhesives are applied on concrete base as well as on bottom of PVC tiles. Then the tile is pressed gently with 5 kg wooden roller till the oozing of adhesive is seen. The oozed out adhesive is wiped and the floor is washed with warm soap water. The floor finish is smooth, attractive and can be easily cleaned.
    However it is slippery and costly.

Question 25

What are stairs?

Answer 25

Stairs give access from floor to floor. The space/room housing stairs is called staircase. Stairs consists of a number of steps arranged in a single flight or more number of flights.

Question 26

List the Requirements of good stairs

Answer 26

Requirements of good stairs
1. Width: 0.9 m in residential buildings and 1.5 m to 2.5 m in public buildings.
2. Number of Steps in a Flight: Maximum number of steps in a flight should be limited to 12to 14, while minimum is 3.
3. Rise: Rise provided should be uniform. It is normally 150 mm to 175 mm in residential buildings while it is kept between 120 mm to 150 mm in public buildings.
However in commercial buildings more rise is provided from the consideration of economic floor area.
4. Tread: Horizontal projection of a step in a stair case is called tread. It is also known as going. In residential buildings tread provided is 250 mm while in public buildings it is 270 mm to300 mm.
5. Head Room: Head room available in the stair case should not be less than 2.1 m.
6. Hand Rails: Hand rails should be provided at a convenient height of a normal person
which is from 850 mm to 900 mm.

Question 27

List the Types of staircase

Answer 27

Straight Stairs
Dog Legged Stairs
Well or Open-newel Stairs
Geometrical Stair
Spiral Stairs
Turning Stairs

Question 28

Explain the types of stairs

Answer 28

Straight Stairs: If the space available for stair case is narrow and long, straight stairs may
be provided. Such stairs are commonly used to give access to porch or as emergency exits to cinema halls. In this type all steps are in one direction. They may be provided in single flight or in two flights with landing between the two flights

Dog Legged Stairs: It consists of two straight flights with 180° turn between the two. They are very commonly used to give access from floor to floor.

Well or Open-newel Stairs: It differs from dog legged stairs such that in this case there is0.15 m to 1.0 m gap between the two adjacent flights.

Geometrical Stair: This type of stair is similar to the open newel stair except that well formed between the two adjacent flights is curved. The hand rail provided is continuous.

Spiral Stairs: These stairs are commonly used as emergency exits. It consists of a central post
supporting a series of steps arranged in the form of a spiral. At the end of steps continuous hand rail is provided. Such stairs are provided where space available for stairs is very much limited. Cast iron, steel or R.C.C. is used for building these stairs.

Turning Stairs: Apart from dog legged and open newel type turns, stairs may turn in various forms. They depend upon the available space for stairs. Quarter turned, half turned with few steps in between and bifurcated stairs are some of such turned stairs.