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 1m2 window opening.
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.
Window shutters may be fixed, centrally pivoted, sliding type or double hung. Following Figure 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
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.
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. given below. It needs temporary form work at the time of construction. The lintel is to be cured for 7–14 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—main 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.