Short Notes: Floors | Short Notes for Civil Engineering - Civil Engineering (CE) PDF Download

 Page 1


CHAPTER – 12 
FLOORS 
 
In order to sub-divide the portion between the plinth level or basement 
level and roof level, solid constructions are Carrie out. These 
constructions are known as floors and exposed top surface of floors are 
termed as floorings. Ground floors or basement floors, which directly 
rest on the ground, do not require the provision of a floor. But they are 
provided with suitable type of flooring.  
 
12.1  Types of Floors: 
Floors are classified into two categories 
1. Timber Floors 
2. Composite Floors 
 
1. Timber Floors: In this floor, only timber is used as a material. 
Timber floors are further divided into four types. 
a. Basement or Ground floor of timber 
b. Single Joist timber beam 
c. Double Joist timber beam 
d. Framed triple joist timber floor. 
 
Features of Timber Floors: 
(i) Floor Boards: These boards are provided at the top of bridging joists 
and they form the wearing surface of the floor. The width varies from 
100mm to 200mm and thickness varies from 20mm to 40mm. the 
Page 2


CHAPTER – 12 
FLOORS 
 
In order to sub-divide the portion between the plinth level or basement 
level and roof level, solid constructions are Carrie out. These 
constructions are known as floors and exposed top surface of floors are 
termed as floorings. Ground floors or basement floors, which directly 
rest on the ground, do not require the provision of a floor. But they are 
provided with suitable type of flooring.  
 
12.1  Types of Floors: 
Floors are classified into two categories 
1. Timber Floors 
2. Composite Floors 
 
1. Timber Floors: In this floor, only timber is used as a material. 
Timber floors are further divided into four types. 
a. Basement or Ground floor of timber 
b. Single Joist timber beam 
c. Double Joist timber beam 
d. Framed triple joist timber floor. 
 
Features of Timber Floors: 
(i) Floor Boards: These boards are provided at the top of bridging joists 
and they form the wearing surface of the floor. The width varies from 
100mm to 200mm and thickness varies from 20mm to 40mm. the 
Floors                                                                                    
  
thickness may be changes when a floor subject to heavy traffic from 60 
to 80mm. The floor boards are joined and widened by any suitable joint 
as shown in the figure.12.1 
 
Fig 12.1  Pugging 
(ii) Floor Ceilings: To make the underside of the floor flat and to 
improve the appearance as a whole, ceilings may be provided rest on 
bridging joists or binders. The ceilings may consists of plaster boards or 
sheets of asbestors cement or some suitable material. In order to make 
ceilings strong and durable, ceiling joists may be provided at right angles 
to the bridging joists or the binders. 
(i) Pugging: In order to make the timber floor sound proof, 
pugging may be resorted. Pugging plaster is a mixture of 
chopped straw and mortar. Insulating boards supporting on 
fillets are provided and hallows space between the 
floorboards and the insulating boards is filled up with the 
pugging plaster. 
(ii) Trimming: When openings are to be provided in wooden 
floors, it is clear that bridging joists will not rest on the walls. 
In such cases, the process of trimming is required. Trimming 
joists support one or two trimmer joists to which trimmed 
joists are fixed. The trimming joists and trimmer joists have 
Page 3


CHAPTER – 12 
FLOORS 
 
In order to sub-divide the portion between the plinth level or basement 
level and roof level, solid constructions are Carrie out. These 
constructions are known as floors and exposed top surface of floors are 
termed as floorings. Ground floors or basement floors, which directly 
rest on the ground, do not require the provision of a floor. But they are 
provided with suitable type of flooring.  
 
12.1  Types of Floors: 
Floors are classified into two categories 
1. Timber Floors 
2. Composite Floors 
 
1. Timber Floors: In this floor, only timber is used as a material. 
Timber floors are further divided into four types. 
a. Basement or Ground floor of timber 
b. Single Joist timber beam 
c. Double Joist timber beam 
d. Framed triple joist timber floor. 
 
Features of Timber Floors: 
(i) Floor Boards: These boards are provided at the top of bridging joists 
and they form the wearing surface of the floor. The width varies from 
100mm to 200mm and thickness varies from 20mm to 40mm. the 
Floors                                                                                    
  
thickness may be changes when a floor subject to heavy traffic from 60 
to 80mm. The floor boards are joined and widened by any suitable joint 
as shown in the figure.12.1 
 
Fig 12.1  Pugging 
(ii) Floor Ceilings: To make the underside of the floor flat and to 
improve the appearance as a whole, ceilings may be provided rest on 
bridging joists or binders. The ceilings may consists of plaster boards or 
sheets of asbestors cement or some suitable material. In order to make 
ceilings strong and durable, ceiling joists may be provided at right angles 
to the bridging joists or the binders. 
(i) Pugging: In order to make the timber floor sound proof, 
pugging may be resorted. Pugging plaster is a mixture of 
chopped straw and mortar. Insulating boards supporting on 
fillets are provided and hallows space between the 
floorboards and the insulating boards is filled up with the 
pugging plaster. 
(ii) Trimming: When openings are to be provided in wooden 
floors, it is clear that bridging joists will not rest on the walls. 
In such cases, the process of trimming is required. Trimming 
joists support one or two trimmer joists to which trimmed 
joists are fixed. The trimming joists and trimmer joists have 
slightly greater section than bridging joists Fig. 12.2 shows a 
wooden floor with stair well. 
(iii) Use of stell sections: Binders and girders of wooden floor can 
be replaced by mild rolled steel joists. The only precaution to 
be taken in this case would be to encase the R.S.J. by 
concrete so as to prevent rusting of R.S.J. The use of steel 
section makes the floor light and economical. 
a) Basement or ground floor of timber: 
In auditorium, to carry out dances or dramas timber floors are 
constructed on ground floor. Sleeper walls, which may be of 
one-half brick or one brick thickness, are constructed at 
centre to centre distance of 1.20m to 1.80m. Wall-plates are 
provided along the wall as well as along the sleeper walls and 
they reduce the spans of the building joists and serve as end 
supports for the bridging joists. On wall-plates rest the ends 
of bridging joists, which are usually provided at a centre to 
centre distance of about 30 cm. Finally, floor boards are 
provided to finish up the floor. The details are as shown in fig 
12.2. 
Page 4


CHAPTER – 12 
FLOORS 
 
In order to sub-divide the portion between the plinth level or basement 
level and roof level, solid constructions are Carrie out. These 
constructions are known as floors and exposed top surface of floors are 
termed as floorings. Ground floors or basement floors, which directly 
rest on the ground, do not require the provision of a floor. But they are 
provided with suitable type of flooring.  
 
12.1  Types of Floors: 
Floors are classified into two categories 
1. Timber Floors 
2. Composite Floors 
 
1. Timber Floors: In this floor, only timber is used as a material. 
Timber floors are further divided into four types. 
a. Basement or Ground floor of timber 
b. Single Joist timber beam 
c. Double Joist timber beam 
d. Framed triple joist timber floor. 
 
Features of Timber Floors: 
(i) Floor Boards: These boards are provided at the top of bridging joists 
and they form the wearing surface of the floor. The width varies from 
100mm to 200mm and thickness varies from 20mm to 40mm. the 
Floors                                                                                    
  
thickness may be changes when a floor subject to heavy traffic from 60 
to 80mm. The floor boards are joined and widened by any suitable joint 
as shown in the figure.12.1 
 
Fig 12.1  Pugging 
(ii) Floor Ceilings: To make the underside of the floor flat and to 
improve the appearance as a whole, ceilings may be provided rest on 
bridging joists or binders. The ceilings may consists of plaster boards or 
sheets of asbestors cement or some suitable material. In order to make 
ceilings strong and durable, ceiling joists may be provided at right angles 
to the bridging joists or the binders. 
(i) Pugging: In order to make the timber floor sound proof, 
pugging may be resorted. Pugging plaster is a mixture of 
chopped straw and mortar. Insulating boards supporting on 
fillets are provided and hallows space between the 
floorboards and the insulating boards is filled up with the 
pugging plaster. 
(ii) Trimming: When openings are to be provided in wooden 
floors, it is clear that bridging joists will not rest on the walls. 
In such cases, the process of trimming is required. Trimming 
joists support one or two trimmer joists to which trimmed 
joists are fixed. The trimming joists and trimmer joists have 
slightly greater section than bridging joists Fig. 12.2 shows a 
wooden floor with stair well. 
(iii) Use of stell sections: Binders and girders of wooden floor can 
be replaced by mild rolled steel joists. The only precaution to 
be taken in this case would be to encase the R.S.J. by 
concrete so as to prevent rusting of R.S.J. The use of steel 
section makes the floor light and economical. 
a) Basement or ground floor of timber: 
In auditorium, to carry out dances or dramas timber floors are 
constructed on ground floor. Sleeper walls, which may be of 
one-half brick or one brick thickness, are constructed at 
centre to centre distance of 1.20m to 1.80m. Wall-plates are 
provided along the wall as well as along the sleeper walls and 
they reduce the spans of the building joists and serve as end 
supports for the bridging joists. On wall-plates rest the ends 
of bridging joists, which are usually provided at a centre to 
centre distance of about 30 cm. Finally, floor boards are 
provided to finish up the floor. The details are as shown in fig 
12.2. 
Floors                                                                                    
  
 
Fig 12.2. Basement or ground floor of timber 
b) Single Joist timber floor:  
These floors consist of single joist, which are placed below 
the floorboards. The joists are usually placed at a centre to 
centre distance of 30cm to 45cm. The joists are supported on 
wall-plates at their ends. A space of about 50mm is kept for 
the circulation of air as shown in fig 12.3. Single joist timber 
floor can be adopted for a maximum span of about 3.6m. 
When the span of joist exceeds 2.4m, it becomes necessary to 
strengthen the joist by providing bearing bone strutting. In 
this arrangement, inclined timber pieces are firmly fixed 
between the joists and the ends of these struts are nailed to the 
joist. At the end, wedges are provided between the wall and 
the joists.  
Page 5


CHAPTER – 12 
FLOORS 
 
In order to sub-divide the portion between the plinth level or basement 
level and roof level, solid constructions are Carrie out. These 
constructions are known as floors and exposed top surface of floors are 
termed as floorings. Ground floors or basement floors, which directly 
rest on the ground, do not require the provision of a floor. But they are 
provided with suitable type of flooring.  
 
12.1  Types of Floors: 
Floors are classified into two categories 
1. Timber Floors 
2. Composite Floors 
 
1. Timber Floors: In this floor, only timber is used as a material. 
Timber floors are further divided into four types. 
a. Basement or Ground floor of timber 
b. Single Joist timber beam 
c. Double Joist timber beam 
d. Framed triple joist timber floor. 
 
Features of Timber Floors: 
(i) Floor Boards: These boards are provided at the top of bridging joists 
and they form the wearing surface of the floor. The width varies from 
100mm to 200mm and thickness varies from 20mm to 40mm. the 
Floors                                                                                    
  
thickness may be changes when a floor subject to heavy traffic from 60 
to 80mm. The floor boards are joined and widened by any suitable joint 
as shown in the figure.12.1 
 
Fig 12.1  Pugging 
(ii) Floor Ceilings: To make the underside of the floor flat and to 
improve the appearance as a whole, ceilings may be provided rest on 
bridging joists or binders. The ceilings may consists of plaster boards or 
sheets of asbestors cement or some suitable material. In order to make 
ceilings strong and durable, ceiling joists may be provided at right angles 
to the bridging joists or the binders. 
(i) Pugging: In order to make the timber floor sound proof, 
pugging may be resorted. Pugging plaster is a mixture of 
chopped straw and mortar. Insulating boards supporting on 
fillets are provided and hallows space between the 
floorboards and the insulating boards is filled up with the 
pugging plaster. 
(ii) Trimming: When openings are to be provided in wooden 
floors, it is clear that bridging joists will not rest on the walls. 
In such cases, the process of trimming is required. Trimming 
joists support one or two trimmer joists to which trimmed 
joists are fixed. The trimming joists and trimmer joists have 
slightly greater section than bridging joists Fig. 12.2 shows a 
wooden floor with stair well. 
(iii) Use of stell sections: Binders and girders of wooden floor can 
be replaced by mild rolled steel joists. The only precaution to 
be taken in this case would be to encase the R.S.J. by 
concrete so as to prevent rusting of R.S.J. The use of steel 
section makes the floor light and economical. 
a) Basement or ground floor of timber: 
In auditorium, to carry out dances or dramas timber floors are 
constructed on ground floor. Sleeper walls, which may be of 
one-half brick or one brick thickness, are constructed at 
centre to centre distance of 1.20m to 1.80m. Wall-plates are 
provided along the wall as well as along the sleeper walls and 
they reduce the spans of the building joists and serve as end 
supports for the bridging joists. On wall-plates rest the ends 
of bridging joists, which are usually provided at a centre to 
centre distance of about 30 cm. Finally, floor boards are 
provided to finish up the floor. The details are as shown in fig 
12.2. 
Floors                                                                                    
  
 
Fig 12.2. Basement or ground floor of timber 
b) Single Joist timber floor:  
These floors consist of single joist, which are placed below 
the floorboards. The joists are usually placed at a centre to 
centre distance of 30cm to 45cm. The joists are supported on 
wall-plates at their ends. A space of about 50mm is kept for 
the circulation of air as shown in fig 12.3. Single joist timber 
floor can be adopted for a maximum span of about 3.6m. 
When the span of joist exceeds 2.4m, it becomes necessary to 
strengthen the joist by providing bearing bone strutting. In 
this arrangement, inclined timber pieces are firmly fixed 
between the joists and the ends of these struts are nailed to the 
joist. At the end, wedges are provided between the wall and 
the joists.  
 
Fig 12.3 Details of single joist timber floor 
c) Double joist timber floors:  
In this type of floors, intermediate supports known as binders, 
are provided for bridging joists. Binders are generally placed 
at a centre to centre distance of 1.80m to 2.40m as shown in 
fig 12.4. The ends of binders rest on wooden or stone blocks. 
Double joist timber floors are stronger than the single joist 
timber floors. They prevent the passage of sound in better 
way and they are suitable for spans of 3.60 to 7.50m. This 
type of floors has following disadvantages. 
(i) The weight of floor is thrown on few points in a wall. 
(ii) Depth of floor is increased by the use of binders and 
accordingly height of the room is decreased.