Types of Floor

The various types of floor commonly used are as follows.

Basement or ground timber floor

Timber floors are constructed on ground floors, generally in theatres. Several sleeper walls or dwarf walls of half brick thickness or full brick thickness are constructed at an interval of 1.5 m to support the timber floor. Wall plates are placed on walls and sleeper walls to support the joists supporting the floors. The joists are provided at a distance of about 30 cm and the timber planks are closely fitted over the joists to provide the floor. The arrangement for proper air circulation is made in the floor, otherwise timber will be attacked by dry rot. The following precautions are recommended:

1. Well-seasoned timber should be used in the construction of such floors.
2. Plain cement concrete 1:2:4 of 10 cm thickness is to be provided over the soil beneath the timber floor.
3. The empty space between the floor and the concrete base should be filled up with sand.
4. The damp proofing courses are to be placed in the external walls and at the top of the sleeper walls.

Single joist timber floor

This type of floor is used for residential buildings where spans are comparatively small and the loads are lighter. The wooden joists are placed at about 30 cm centre to centre, spanning the rooms in the shorter direction. Wooden planks are laid over these joists. The timber joists are supported on wall plates. Corbels may be required to support the joists if the width of the wall is not sufficient. Joists must be strong enough to withstand the loads and at the same time they should not deflect too much. If the length of the joist is more than 3.5 m, then struts are provided in the joists to check side buckling. The wooden planks are about 4 cm thick and 10–15 cm wide.

Advantages

1. Single joist timber floors are simple to construct.
2. They require less initial cost.
3. Distribution of loads on the wall is more uniform as the joists are spaced closely.

Disadvantages

1. The joists may sag and, hence, cracks will develop in the ceilings.
2. They are not soundproof.
3. Deep joists are required for larger spans that increase the weight and construction cost of the floor.
4. The loads are transmitted to the openings such as windows or door lintels because of evenly spaced joists.

Double joist timber floor

This type of floor is stronger than the single joist timber floor. They are used for longer spans of 3.6–7.5 m and prevent the travel of sound waves to a great extent. Intermediate supports called binders are placed for bridging the joists. Binders are spaced at a centre-to-centre distance of about 2 m. The ends of binders are kept on wooden or stone blocks and they should not be embedded in the masonry wall. The ceilings may be fixed to the bottom of the binders by fixing a ceiling joist to the binders. Lathing is fixed to the ceiling joist.

Advantages

1. The loads are transmitted to the wall at certain specified points and, hence, door and window openings may be avoided.
2. This is a more rigid type of flooring and, hence, there is less chance of developing cracks in the plastered ceiling.
3. It is more soundproof.
4. The use of additional binders near the walls can eliminate the need of wall plates.

Disadvantages

1. More labour is required
2. The depth of the floor is considerably increased and, thus, the head room is reduced

Framed timber floor

This type of timber floor is used for spans of more than 7.5 m. Girders are placed between the walls and the binders are put on the girders and the bridging joists rest on the binders. The spacing between girders depends on the type and size of the girder and the size of the binders. The ends of girders are put on stone or concrete templates in the wall. The ceilings are fixed directly to the binders or ceiling joists may be employed.

Filler joist floor

Small sections of rolled steel joists are encased in the concrete. The joist is supported on walls or on steel beams. The joists are placed at a centre-to-centre distance of 60–90 cm and act as reinforcement in the concrete. The rolled steel joists and beams should be completely encased in the concrete.

Jack arch floor

Bricks or concrete may be used for the construction of jack arch floor. The arches are provided between the lower flanges of rolled steel joists at a centre distance of not more than 1.5 m. The rise of the arch is generally one-twelfth of the span. Mild steel ties are provided in the end spans to take up the tension developed due to the arch action of the floor. The diameter of tie rods is 18–25 mm and their spacing is 1.8–2.4 m. In addition, they are rigidly fixed on the walls, the side filling is done by lime concrete and the desired floor covering is provided. Plain ceiling is not obtained in this case and it may be considered as a shortcoming of such construction.

Double flagstone floor

For spans less than 4 m only rolled steel joists are placed, but if the span exceeds 4 m, a framework of rolled steel beams and joists is formed. Flagstones of about 40 mm thickness and proper width are placed on the lower flanges and upper flanges. The joints of flagstones in the top layer are given a fine finish for improved appearance. The empty space is filled up with selected earth.RCC floor

Flat slab floor

It is directly supported on the columns without providing any intermediate beams. This type of construction is adopted when the use of beams is forbidden.

Advantages

1. More clear head room is available for use.
2. Even for quite heavy loads, thinner slabs are required.
3. No projecting of beams is to be seen and, therefore, the need of false ceiling is eliminated.
4. It is convenient to make lighting arrangements.
5. The framework and construction of flat slabs are simpler.

Flat slabs are commonly used in commercial buildings, factories and warehouses, etc., but they are not economical for lighter loads.

Hollow tiled ribbed floor

To reduce the weight of a solid floor structure, a hollow tiled ribbed floor is constructed. In this type of construction, hollow blocks of clay or concrete are used. These hollow bricks or tiles are placed at about 10 cm apart. In this space of 10 cm, mild steel bars of 8–12 mm diameter are placed. The surfaces of the hollow tiles are kept rough to develop a better bond with the surrounding concrete. A minimum cover of 8 cm is provided at the top of the tiles. The empty spaces are filled up with concrete. These floors are fireproof, soundproof, damp proof, light and economical. A properly designed floor of this type can carry considerably heavy loads.