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  • 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.
    The requirement of good stairs are
    a) Width: 0.9 m in residential buildings and 1.5 m to 2.5 m in public buildings.
    (b) Number of Steps in a Flight: Maximum number of steps in a flight should be limited to 12 to 14, while minimum is 3.
    (c) 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.
    (d) 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 to 300 mm.

    The following empirical formula is used to decide rise and tread:
    2R + T > 550 mm but < 700 to 600 mm
    whereR is rise in mm and T is tread in mm.
    (e) Head Room: Head room available in the stair case should not be less than 2.1 m. (f) Hand Rails: Hand rails should be provided at a convenient height of a normal person which is from 850 mm to 900 mm.

    Types of Stairs
    The stairs may be built with wood, concrete masonry or with cast iron. Wooden stairs are not safe,
    because of the danger of fire. However they are used in unimportant buildings to access to small areas
    in the upper floors. Cast iron or steel stairs in the spiral forms were used commonly to reduce stair case
    area. In many residential buildings masonry stairs are also used. Reinforced concrete stairs are very
    commonly used in all types of buildings.
    Based on the shapes stairs may be classified as:
    (a) Straight stairs
    (b) Dog legged stairs
    (c) Well or open-newel stairs
    (d) Geometrical stairs
    (e) Spiral stairs
    (f) Turning stairs.


    (a) 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 [Fig. 8.35].

    Dog Legged Stairs: It consists of two straight flights with 180¬į turn between the two. They are very commonly used to give access from floor to floor. Figure 8.36 shows the arrangement of steps in such stairs.

    (c) Well or Open-newel Stairs: It differs from dog legged stairs such that in this case there is
    0.15 m to 1.0 m gap between the two adjacent flights. Figure 8.37 shows a typical opennewel stair.

    (d) 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. [Ref. Fig. 8.38]

    (e) 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. Figure 8.39 shows a typical spiral stair. Cast iron, steel or R.C.C. is used for building these stairs.

    ( f ) 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. Figure 8.40 shows a bifurcated stair.

    Salient Points to be Considered in Locating Stairs
    The following points should be considered in locating stairs in a building:
    (a) They should be located near the main entrance to the building.
    (b) There should be easy access from all the rooms without disturbing the privacy of the rooms.
    (c) There should be spacious approach.
    (d) Good light and ventilation should be available.

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  • Lintel is a horizontal flexural member which spans over the openings in the walls for doors, windows,¬†ventilators, cupboards etc. The load of masonry above the opening is transferred to the wall by flexural¬†action of the lintel so that frames of doors, windows etc are not unduly loaded. The end bearings for the¬†lintel should be at least 200 mm. The width of lintels is same as that of wall.
    Lintels of various materials are used. They are:
    (a) Wood
    (b) Stone
    (c) Brick
    (d) R.C.C. and
    (e) Steel.

    (a) Wood Lintel: It may be a single piece or may be assembled by joining 2 to 3 pieces. Sometimes the wooden lintels are strengthened by steel plates at top and bottom. Such lintels are called as flitched beams.

    (b) Stone Lintels: Wherever stones are available stone beams are used as lintels. As stone is weak in tension they can be used only for small spans. Their depth is kept about 1 /10 th span.
    Stones are cut to the width of wall and dressed before using as lintels.

    (c) Brick Lintels: Well burnt, good quality lintels are laid on ends or edges to form lintels as ¬†shown in Fig. 8.34. It needs temporary form work at the time of construction. The lintel is to¬†be cured for 7‚Äď14 days before form work is removed. Such lintels are useful to span small¬†openings.

    (d) R.C.C. Lintels: It is possible to provide R.C.C. lintels of any span required in the building.
    They can be isolated or continuous over the openings. They are provided with suitable reinforcement‚ÄĒmain reinforcements beings on lower side in the opening. Nowadays these lintels are used very commonly in buildings.

    (e) Steel Lintels: Steel angles or rolled steel I-sections are used as lintels. Tube separators may be provided to maintain the spacing between the sections. If the sections are opened to atmospheric action, regular painting is necessary. Many times they are encased in concrete to avoid maintenance problem. These lintels can be used for large openings.

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  • 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 √ó 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 √ó 1.9 m. As a
    thumb rule height of door should be 1 m more than its width.

    Windows are provided to give light and ventilation. They are located at a height of 0.75 m to 0.90 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 at least 1 m2 window opening.

    Types of Doors

    Various types of doors are in use which may be classified on the basis of arrangement of shutters, method of constructions, principles of working operations and materials used. Commonly used doors are briefly explained below:

    1. 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.

    Battened, Ledged and Braced Doors: If doors are wide apart from using battens and ledges diagonal members, known as braces, are provided to strengthen the door. Figure 8.22 shows a typical battened, ledged and braced door.


    Some times above two types of shutters are provided within wooden frame work and in those cases they may be called as battened, ledges and framed doors.

    3. 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. Figure 8.23 show few types of panelled doors. If glass panels are used they may be called as glazed doors.

    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. Nowadays flush doors are commonly used in residential and office buildings. Figure 8.24 shows typical flush door.

     

    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. [Fig. 25]

    Revolving Doors: It consist 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 madeup of glass. A circular space of entrance is provided within which shutters rotate. As shutters rotate they give entrance on one side and exit on other side. These doors are preferred in public buildings like stores, banks, hotels, theatres where continuous use of doors is necessary. They are very much required in entrance to air conditioned public buildings. Figure 8.26 shows a typical revolving door.

    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. Since these doors can open on both sides it is desirable to provide glass panels or peep holes to enable user to see the persons from other side. [Fig. 8.27]

    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. Such doors are used in banks, offices etc. The arrangement of such shutters in plan is shown in Fig. 8.28

    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

    as shown in Fig. 8.29. The rollers are provided at their top as well as at bottom so that shutter can be pulled or pushed side ways with slight force. There may be single or double shutters. Usually these doors are used for additional safety. They are commonly used for front doors, bank locker rooms, school and college entrance doors.

    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. For this counterbalancing is made with helical springs on the drum. The shutter can be easily pulled down. This type of doors are commonly used as additional doors to shops, offices, banks, factory, buildings from the point of safety.

    Table 8.7 gives the differences between collapsible and revolving doors.

    Types of Windows

    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. Timber may get termite attacks, steel may rust but aluminium do not have any such defects. However they are costly.
    Shutters of windows may be panelled, glazed or louvered. Louvered windows are generally used for bathrooms and toilets where vision is not to be allowed but ventilation is required. Lower parts panelled and upper parts glazed windows are commonly used. Instead of panelled one may think of using translucent glasses. Figure 8.31 show a louvered windows.

    Window shutters may be fixed, centrally pivoted, sliding type or double hung. Figure 8.32 shows a typical double hung window.

    Depending upon the position of windows, they may be classified as:
    (a) Casement windows
    (b) Bay windows
    (c) Corner windows

    (d) Clear storey windows
    (e) Gable windows
    (f) Sky light windows
    (g) Dormer windows
    (h) Ventilators

    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.
    Bay windows are provided on the projected portion of walls.
    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.
    Clear storey windows are provided when the height of the room is much more than adjacent room/varandah. It is provided between the gap of low height room and the top of room with greater height.
    Gable windows are provided in the gable portion of the building. They are required in the stair cases or in the halls with gable walls.
    Sky light windows are provided on a sloping roof. It projects above the top sloping surface. The common rafters are to be trimmed suitably.
    Dormer windows are vertical windows on the sloping roof.
    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.
    Various type of windows based on their positions are shown in Fig. 8.33

     

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  • 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.

    Flat roofs are used in plains where rainfall is less and climate is moderate. Pitched roofs are
    preferred wherever rainfall is more. Shells and folded plate roofs are used to cover large
    column free areas required for auditoriums, factories etc. Brief description of these roofs is
    presented below:

    1. Flat Roofs: These roofs are nearly flat. However slight slope (not more than 10¬į) 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:

    (a) The roof can be used as a terrace for playing and celebrating functions.
    (b) At any latter stage the roof can be converted as a floor by adding another storey.
    (c) They can suit to any shape of the building.
    (d) Over-head water tanks and other services can be located easily.
    (e) They can be made fire proof easily compared to pitched roof.
    The disadvantages of flat roofs are:
    (a) They cannot cover large column free areas.
    (b) Leakage problem may occur at latter date also due to development of cracks. Once leakage problem starts, it needs costly treatments.
    (c) The dead weight of flat roofs is more.
    (d) In places of snow fall flat roofs are to be avoided to reduce snow load.
    (e) The initial cost of construction is more.
    (f) Speed of construction of flat roofs is less.

    Types of Flat Roofs: All the types listed for upper floors can be used as flat roofs.

    2. Pitched Roofs: In the areas of heavy rain falls and snow fall sloping roof are used. The slope of roof shall be more than 10¬į. They may have slopes as much as 45¬į to 60¬į also. The sloped roofs 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 like A.C. sheet, G.I. sheets, tiles, slates etc. are supported on suitable structures. The pitched roofs are classified into

    (a) Single roofs (b) Double or purlin roofs
    (c) Trussed roofs.

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

    (i) Lean to roofs (ii) Coupled roofs
    (iii) Coupled-close roof (iv) Collar beam roof
    In all these roofs rafters placed at 600 mm to 800 mm spacing are main members taking load of the roof. Battens run over the rafters to support tiles. Figure 8.13 shows various types of single roofs.

    (b) Double or Purlin Roofs: If span exceeds, the cost of rafters increase and single roof becomes uneconomical. For spans more than 5 m double purlin roofs are preferred. The intermediate support is given to rafters by purlins supported over collar beams. Figure 8.14 shows a typical double or purlin roof.

    (c) Trussed Roof: If span is more, a frame work 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 in turn support roof sheets. For spans up to 9 m wooden trusses may be used but for larger spans steel trusses are a must. In case of wooden trusses suitable carpentry joints are made to connect various members at a joint. Bolts and straps are also used. In case of steel trusses joints are made using gusset plates and by providing bolts or rivets or welding.
    Depending upon the span, trusses of different shapes are used. End of trusses are supported on walls or on column. Figure 8.15 shows different shapes of trusses used. Figure 8.16 shows a typical wooden truss details and Fig. 8.17 shows the details of a typical steel truss.


    Shells and Folded Plate Roofs: 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. Caves are having natural shell roofs. An examination of places of worships built in India, Europe and Islamic nations show that shell structures were in usage for the last 800 to 1000 years. However the shells of middle ages were massive masonry structures but nowadays thin R.C.C. shell roofs are built to cover large column free areas. Figure 8.18 shows commonly used shell roofs.

    Advantages and Disadvantages of Shell Roofs
    Advantages of shell roofs are:
    (a) Good from aesthetic point of view
    (b) Material consumption is quite less
    (c) Form work can be removed early
    (d) Large column free areas can be covered.

    Disadvantages are:
    (a) Top surface is curved and hence advantage of terrace is lost.
    (b) Form work is costly.
    Folded plate roofs may be looked as slab with a number of folds. These roofs are also known as hipped plates, prismatic shells and faltwerke. In these structures also bending is reduced and lot of load gets transferred as membrane compression. However folded plates are not so efficient as shells.
    Figure 8.19 shows typical folded plate roofs.

    Advantages and Disadvantages of Folded Plate Roofs Over Shell Roofs
    Advantages are:

    (a) Form work required is relatively simpler.
    (b) Movable form work can be employed.
    (c) Design involves simpler calculations.

    Disadvantages are:
    (a) Folded plate consume more material than shells.
    (b) Form work can be removed after 7 days while in case of shells it can be little earlier.

    Roof Coverings for Pitched Roofs
    Various types of covering materials are available for pitched roofs and their selection depends upon the climatic conditions, fabrication facility, availability of materials and affordability of the owner. Commonly used pitched roof covering materials are:

    (a) Thatch (b) Shingle
    (c) Tiles (d) Slates
    (e) Asbestos cement (A.C.) sheets ( f ) Galvanised iron (G.I.) sheets

    (a) Thatch Covering: These coverings are provided for small spans, mainly for residential buildings in villages. Thatch is a roof covering of straw, reeds or similar materials. The thatch is well-soaked in water or fire resisting solution and packed bundles are laid with their butt ends pointing towards eves. Thickness varies from 150 mm to 300 mm. They are tied with ropes or twines to supporting structures. The supporting structure consists of round bamboo rafters spaced at 200 mm to 300 mm over which split bamboos laid at right angles at close spacing. It is claimed that reed thatch can last 50 to 60 years while straw thatch may last for 20‚Äď25 years.

    The advantage of thatch roof is they are cheap and do not need skilled workers to build them. The disadvantages are they are very poor fire resistant and harbour rats and other insects.

    (b) Shingles: Wood shingles are nothing but the split or sawn thin pieces of wood. Their size varies from 300 mm to 400 mm and length from 60 mm to 250 mm. Their thickness varies from 10 mm at one end to 3 mm at the other end. They are nailed to supporting structures.
    They are commonly used in hilly areas for low cost housing. They have very poor fire and termite resistance.

    (c) Tiles: Various clay tiles are manufactured in different localities. They serve as good covering
    materials. Tiles are supported over battens which are in turn supported by rafters/trusses etc.
    Allahabad tiles, Mangalore tiles are excellent inter-locking tiles. They give good appearance also.

    (d) Slates: A slate is a sedimentary rock. Its colour is gray. It can be easily split into thin sheets.
    Slates of size 450 mm to 600 mm wide, 300 mm long and 4 to 8 mm thick are used as covering materials of pitched roofs in the areas where slate quarries are nearby. A good slate is hard, tough, durable. They are having rough texture and they give ringing bell like sound when struck. They do not absorb water.

    (e) A.C. Sheets: Asbestos cement is a material which consists of 15 per cent of asbestos fibres evenly distributed and pressed with cement. They are manufactured in sufficiently large size.
    The width of a A.C. sheet varies from 1.0 to 1.2 m and length from 1.75 to 3.0 m. To get sufficient strength with thin sections they are manufactured with corrugation or with traffords [Fig. 8.20]. They are fixed to the steel purlins using J-bolts. The roofing is quite economical, waterproof. However not very good thermal resistant. They are commonly used as covering materials in ware houses, godowns or for larger halls. In auditorium etc., if these sheets are used, false ceilings are provided to get good thermal resistance.

    ( f ) G.I. Sheets: Galvanised iron corrugated sheets are manufactured in the sizes 1.0 to 1.2 m wide and 1.65 m length. Galvanisation of iron makes them rust proof. They are fixed to steel purlins using J-bolts and washers. They are durable, fire proof, light in weight and need no maintenance. They are commonly used as covering materials for ware houses, godown, sheds etc. Table 8.6 gives comparison between GI and AC sheets for roof covering.

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  • 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.

    Ground Floor

    Apart from giving good finished surface, these floors should have good damp resistance. The ground surface is rammed well and a layer of red earth or sand is placed which is compacted. A layer of broken bricks, stones etc. is provided up to 150 mm below floor finish level and rammed. While ramming the surface is kept moist to get good compaction. Then 1 : 4 : 8 concrete of 100 to 150 mm thickness is provided as base course. Over this bed floor finish is laid.

    The types of flooring used are:

    1. Mud and moorum 2. Brick
    3. Flag stone 4. Cement concrete
    5. Terrazo 6. Mosaic
    7. Marble 8. Tiles
    9. Timber 10. Rubber
    11. P.V.C.
    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-base course¬†and wearing coat. Base course is laid over well compacted soil. Its thickness is usually 75¬†mm to 100 mm. It consists of lean cement concrete mix (1 : 4 : 8) or lime concrete containing¬†40% of 1 : 2 lime mortar and 60% of coarse aggregate of 40 mm size. After base coarse is¬†hardened wearing coat of 40 mm is laid. It consists of panels of 1 m √ó 1 m, 2 m √ó 2 m or 1 m¬†√ó 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. To get good bond between base coarse and wearing¬†coat cement slurry wash is given before laying wearing coat panels. After 3‚Äď4 days of laying¬†of one set of panel, another alternate panels are laid. Top of these panels are finished by¬†tamping the surface with wooden floats and tapping with trowels, till cement slurry appears
    on top. It needs curing for 7 to 14 days. To get good appearance many times red-oxide
    finishing coat is provided.

    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 terrazo¬†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 20¬†hours, it is cured for 2‚Äď3 days.
    Then grinding is made in the following three steps:
    Ist grinding‚ÄĒUsing coarse grade (No. 60) carborundum stones.
    IInd grinding‚ÄĒUsing medium grade (No. 120) carborundum stones.
    IIIrd grinding‚ÄĒUsing fine grade (No. 320) carborundum stones.
    Plenty of water is used during grinding. After each grinding cement grout of cream-like
    consistency is applied and cured for 6‚Äď7 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 China  glazed 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 Flooring: Marble 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. Tiles of clay, cement or terrazo of standard sizes are manufactured in factories under controlled conditions. On the concrete base, 25 mm to 30 mm thick mortar is laid and these tiles are placed and pressed with trowel or wooden mallet. Before placing tiles care is taken to see that, neat cement slurry is applied to bottom side and sides of tiles to get good bond. 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.

    Upper Floors

    In olden days upper floors were made of timber floors or steel joist and stone slabs. For larger spans jack arch floorings were used. Jack arch floor consisted of I-section steel beams supported on walls and gap between I-sections beams filled with concrete arch. Figure 8.8 shows a typical jack arch flooring.

    Nowadays R.C.C. floors are commonly used. It may consist of only slab, if span is less or it may be beam and slab flooring. In halls of hotels and assembly, many provide flat slabs i.e. slabs directly supported over columns. The columns are provided with widened portion called column head. They give elegant look to halls, particularly when the head room is high. R.C.C. floors need proper thickness and reinforcements. They are arrived at by structural design engineers. Figure 8.9 shows typical R.C.C. slabs.

    In R.C.C. concrete is used to resist compression and steel to resist tension. Hence the concrete in tension zone do not contribute in resisting the load. It just keeps the steel at required position. In reinforced brick slab an attempt is made to replace concrete in tension zone by bricks. It is better thermal efficient than solid concrete floors. Figure 8.10 shows a typical reinforced brick slab.

    In ribbed or hollow tiled flooring, the concrete in tension portion is replaced by hollow tiles. Figure 8.11 shows a typical floor of this type.

    In precast concrete floor panels may be used which helps in avoiding form works, storing of sand, coarse aggregates etc. at the site and also curing. Factories manufacture these units which are to be placed over supports in the structure. Figure 8.12 shows the cross-section of a typical precast floor unit. These units are available in 0.25 m widths and in various spans. Interlocking grooves are provided on the sides to get tight connection with adjoining units.

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