TYPES OF GROUND FLOORS

As the ground floor directly rests on the ground, there is no need for a sub-floor. In order to drain the water outside completely, adequate drainage arrangements have to be made beneath the floor.

In normal practice, the space above the ground, up to a height of about 25–30 cm below the plinth level, called the basement, is filled with some inert materials like sand, gravel, crushed stone, cinder, etc. Over this course, a damp-proof course if needed is laid. Otherwise the floor covering is laid directly on the uniform bed.

The materials used for ground floor construction are: bricks, stones, concrete, hollow concrete blocks or wooden blocks.

The materials generally used for floor coverings are bricks, concrete, terrazo tiles, marbles, stones, mosaic, wood, etc.

Stone Floors

Usual sizes of stones of 30 cm × 30 cm, 45 cm × 45 cm or 60 cm × 60 cm with a thickness of 2–4 cm are used. Generally square stone slabs of the above sizes are used but the slabs can be of rectangular or oblong in shape with square edges. Stone slabs are laid on concrete bedding.

Before laying the slab a base is prepared after excavating to the required depth and the earthen base is levelled, rammed and watered. A layer of lime concrete of thickness 10–45 cm is spread over which the concrete bed or sub-grade is laid.

After setting the stone floor with a slope of 1 in 40, the mortar joints are raked out to a depth of 2 cm and flush pointed with cement mortar of 1 : 3.

Following aspects are kept in mind while laying stone slabs, Fig. 23.1:

1. To begin with two stone slabs from diagonally opposite corners are laid. A string is stretched touching these corner slabs so as to fix top level of the floor.
2. Intermediate slabs are placed from both the sides taking care that the tops of stone slabs are touching the string which ensures the provision of proper grade.
3. All stone slabs should be of uniform thickness, strength and well drained on edges for residential and public buildings.
4. Width of joints between the slabs should not exceed 0.5 cm.
5. Rough surface stone, may be used for godown, sheds, stores, etc.

Figure 23.1 Stone flooring

Brick Floors

This type of flooring is used in case of warehouses, stores and godowns. This is a cheap construction and used in areas when stones are not available but good quality bricks are available.

This flooring may be laid flat or on edge. They may be arranged in herring bone pattern or at right angles to the walls. Brick on edge is preferred compared to bricks laid flat as the brick on edge is less liable for crack under pressure because of the higher depths. The bricks, in both the cases, are laid on ordinary mortar and pointed with cement or set in hydraulic mortar.

The construction of brick flooring is done as explained below, Fig. 23.2:

1. An excavation of about 40 cm depth below the intended level of the floor is made.
2. The earth surface is levelled, watered and well rimmed until it is dry and hard.
3. Over the earth, above a sub-grade of 25 cm depth consisting of rubble or brickbats is laid.
4. Over this, a 10–15 cm thick layer of lime concrete or lean cement concrete (1:3:6) is laid.
5. Upon this prepared sub-grade, bricks are laid in the desired shape.

Figure 23.2 Brick flooring

Concrete Floors

Concrete floorings are mostly used in all residential, commercial and public buildings. The flooring is constructed adopting either monolithic or non-monolithic construction.

In the monolithic construction, after laying the base course layer, immediately a concrete topping is provided. In this type of construction, only a small thickness is needed for wearing surface as the bond between the base course and the wearing surface is good.

But this type of flooring has got several disadvantages as explained below:

1. The wearing surface is susceptible for damage due to subsequent floor use.
2. As the base course if undergoing only small settlement immediately, there is a possibility for hair cracks.
3. Repairing the damaged top surface is difficult.
4. The progress is slow as the base course has to settle.

Non-monolithic construction is sound as the wearing surface is laid only after adequate drying of base course. The floor finish generally used is ordinary concrete finish of 1: : 3 (Fig. 23.3). Under controlled conditions, a mix of 1:2:4 ratio with carefully selected aggregates may be used.

Figure 23.3 Concrete flooring

For non-monolithic construction, the surface of the base concrete is brushed with a stiff broom and cleaned thoroughly. The surface is wetted and excess water removed. The floor is laid in rectangular panels not greater than 2 × 2 m. Generally alternate bays are concreted so as to avoid initial shrinkages. When the concrete layer is even, the surface is rapidly compacted by remaining or beating and screeded to a uniform level. Then trowelling is done to give a level smooth surface. Adequate curing is done for 7 days by spreading a layer of wet sand or special membrane may be used.

Granolithic Floors

It is a concrete flooring with a different type of floor finish called granolithic. Granolithic finish is a concrete made of special selected aggregate. The thickness of layer varies from 1.25 to 4 cm. When it is greater than 4 cm this may be laid monolithically or after the base concrete has hardened.

This flooring is made with very hard and tough quality aggregate in rich concrete of 1:1: 2. Generally hard fine grained granite, basalt, limestone and quartzite stones are suitable for coarse aggregate. In order to get a better granolithic finish, aggregate may be crushed and used. The fine aggregates are the natural or crushed sands with a suitable gathering. Non-slippery surfaces can be obtained by adding suitable abrasives. In case of non-monolithic construction, the base course may be prepared as done in concrete flooring. Granolithic flooring has all the advantages of concrete flooring.

Terrazo Floors

Terrazo is a special type of concrete flooring containing marble chips as aggregates. Any designed colour and designs can be obtained by using marble chips of different shades and colour cement.

Terrazo mix of 1: 2 or 1: 3 (1 cement to 2–3 marble chips) is used depending on the size of marble chips. Terrazo finish is of 10 mm thick. The terrazo finish is laid over the concrete base course (as explained in concrete flooring) by two methods.

1. The cement concrete base is covered uniformly by a 6 mm thick sand cushion and a tar paper is placed on this. Over this paper a layer of rich mortar (1 : 3) about 30 mm is placed uniformly.
2. A thin coat of cement is spread over the wet concrete base. This layer is cleaned and a layer of cement mortar 12 mm thick is spread evenly over it. When the mortar bed has hardened the terrazo mix (1 cement: 3 marble chips) of 6 and 12 mm is laid after adding water and making workable mix.

After curing for several days, the surface is polished by means of grinding machine fitted with carborundum grinding stone disc. During grinding the surface is kept wet and small holes or pores are filled with a suitable cement paste matching the surface configuration. The surface is then washed with a weak solution of soft soap in warm water. Such a finished surface gives a pleasing appearance and clean environment.

This type of floor is used in public buildings like banks, hotels, offices, etc., because of its decorative appearance and excellent wear-resisting properties.

Mosaic Floors

For construction of this type of flooring, a hard concrete base is laid first. When the base is wet, a 2 cm thick layer of cement mortar (1: 2) is evenly laid. Over this layer small pieces of broken tiles are arranged in different pattern. After this the inner space between tiles is filled with coloured pieces of marble in the desired fashion.

Following this cement or coloured cement is sprinkled at the top to get a complete floor without pores. Then the surface is rolled by light stone roller till an even surface is obtained. After 24 hours of drying the surface is rubbed with a pumice stone of 20 cm × 20 cm × 7 cm fitted to a long wooden handle. This polished surface is allowed to dry for 2 weeks before put into use.

Tiled Floors

In this type of flooring tiles either of clay or cement concrete, manufactured in different shapes, are used. A 15 cm thick layer or lime or cement concrete is laid over the levelled ground. In order to receive the tiles at 25 mm thick layer of lime mortar (1: 3) or cement mortar (1:1) is laid. A cement slurry is spread over the hardened mortar. Tiles are laid flat on this bed and a cement paste is applied on the sides. Joints are rubbed with carborundum stone after allowing 2–3 days for setting. The entire surface is polished with a pumice stone (Fig. 23.4).

Figure 23.4 Tiled flooring

Tiled floorings are used in residential buildings, hotels, offices and other public buildings. These floors can be constructed in very short time with pleasing appearance and good durability.

Asphalt Floors

Asphalt floorings are of two types, viz., (i) using asphalt tiles and (ii) using mastic asphalt. Asphalt tiles are made from asphalt, asbestos fibres and other materials and pressed under pressure. Asphalt mastic is a mixture of fine aggregates and natural or artificial asphalt.

Asphalt tiles are used to cover wooden or concrete floors. These tiles are resilient, non-absorbent, moisture proof and cheap. They are used in school, offices and hospitals, etc.

Asphaltic mastic can be mixed hot and laid in continuous sheets or pressed into blocks which can be used for flooring. As an alternative it may be mixed with oil and asbestos and applied cold. An ordinary concrete or wood base may be used for laying this mixture.

Marble Floors

High quality marble slabs in the required sizes and colours are available in the market. The construction procedure is same as that of mosaic flooring except that marble slabs or pieces are used instead of mosaic tiles or pieces. This type of flooring is preferred when sanitation and cleanliness are required as in the case of hospitals, temples, theatres and other superior type of works. Now-a-days some quality marbles are used for residential buildings also.

Timber Floors

Timber flooring is not generally preferred for ground floors. If it is used as a ground floor, the prevention of dampness is most important. Timber floorings can be provided in any one of the following methods. Strip flooring consists of narrow and thin strips of wood jointed to each others by tongue and groove joint. Planked flooring is one type in which wider planks are used and they are also of tongued and grooved type. Wooden block flooring consists of small square or rectangular blocks with tongue and groove joints, Fig. 23.5.

Figure 23.5 Wooden block type timber flooring

Timber flooring should have a concrete base or should rest on joints spanning across dwarf walls which are constructed at suitable intervals. For fixing the timber floors on concrete slabs, longitudinal nailing strips are provided. Planked flooring should be laid with spaces of metals spaced 1 mm apart temporarily for providing expansion joints. Strip flooring is used in thickness of 2–2.5 cm and width of 6–10 cm.