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.
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 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.
(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 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.
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 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.
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. 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.
d) Framed or triple joist timber floor:
In this type of floors, intermediate supports, known as girders,
are provided for the binders. Thus, this type of floor consists of girders, binders, bridging joists and floor boards Girders are generally placed at a centre to centre distance of 3 metres. Binders are staggered and connected to girders by tusk and tenon joints. Alternatively, the ends of binders are supported on the iron stirrups, which are fixed to the girders. The ends of girders rest on walls on stone or
concrete templates. This type of timber floor is suitable for
spans greater than 7.50.
II ]Composite Floors:
Floors composed of more than one material are known as
composite floors and they found to possess the following
advantages.
(i) Resist fire and sound in better way than timber floors
(ii) Better hygienic because can be easily cleaned
(iii) Adopted for greater spans.
The following are the types of composite floors
(a) Double flag stone floors
(b) Filler Joists floors
(c) Jack arch floor
(d) R.C.C. floors
(e) Hallow block and rib floors
a) Double flagstone floors:
In this type of floors, flagstones are used in two layers . If span is about 4m, only rolled steel joists are provided and span exceeds 4m, a framework consists of rolled steel beams and joists is formed. Steel beams are placed at a distance of about 3m centre to centre and joists are placed at right angles to beams. Flagstones of about 40mm thickness and of suitable width are fixed on the lower flanges and upper flanges. The joints of top layer of flagstones are finished in a better way to give a nice appearance. Filling of selected earth or concrete is done in the space between the two layers of the flagstones.
b) Filler Joist floors:
In this type of floors, small sections of rolled steel joists are
placed in concrete, this joists may either rest on wall or on
steel beam.The joists act as a reinforced
and are spaced at a centre to centre distance of 60cm to 90cm.
Concrete should completely surround the rolled steel / joists and beams.
c) Jack arch floors:
In this type of floor, brick arches or cement concrete arches
are constructed and these arches rest on the lower flanges of mild steel joists. The joists in turn rest either on wall or on beam. The joists are placed at a distance of about 80cm to 120cm center to center. The rise of arch should be 10cm to 20cm. and the minimum depth of concrete at the crown should be 15cm. The only disadvantage of this floor is that it does not give plain ceiling surface.
d) R.C.C Floor: In this type of floors steel bars and concrete
are used to form a floor. This type of floor is widely used in modern construction. The slab and beam are designed as per loading coming on the floor and proper reinforcement is placed at a suitable place. In case of R.C.C. slab thickness varies from 80mm to 150mm and the main reinforcement is generally in the form of mild steel bars of diameter varying from 9mm to 12mm.
The reinforced concrete may be cast-in-situ or pre-cast, the former
being very common. R.C.C. floors are less costly, durable, easy to
construct and fire-proof. However, they are likely to transmit sound. In any case R.C.C. floors are fast replacing other types of floors.
e) Hallow Block and Rib Floors: In this type of floors, hallow
blocks of clay or concrete are used to reduce the total weight
of the floor. In one form, the blocks are placed 10cm apart
and in this space, mild steel bars are placed.
A minimum cover of 80mm is kept at the top.
Suitable flooring at the top and sealing finish are provided. The blocks are provided with rough or grooved surface so
that they can develop enough bond with the concrete. This
type of floor is economical, fire proof, sound proof and light in weight. If properly designed, this type of floor can even be used to carry heavy loads.
