Post 303 – Gautam Shah
Railings and Parapets are barricades against height related hazards. Railings and parapets both are important functional and architectonic elements. There are few characteristics and elements common to both. It is their nature of construction that places them in separate categories. Both are height-related hazards barriers, mainly for humans. Railings and parapets are invariably smaller than the human height, because most such elements are used for resting or grabbing with hands. For nominal usage 800-900 mm height is adequate, whereas difficult to negotiate (jump-over) conditions a height of 1400-1500 mm is considered. The later height is used for terraces of multi-story buildings to discourage suicides.
Design Parameters > Railings of nominal height ( 800-900mm) must have top 300mm as see-through face, so that children can see out. But if such a separation is likely to provide any toe space to climb up entire face should be see-through. All lattices should have preferably vertical bars and the clear gap must not exceed 100mm. For very tall railings (more than 900 mm) entire face must be of see-through elements and with a squared lattice. The squares in the lattice must not exceed 30 x 30 mm.
Parapets and Railings have sub elements such as: hand rail, Baluster or balustrade, banisters, volute, turn out, goose-neck, rosettes, easing, starting easing, over easing, core rail, newels, fillets, tandem caps, colonnettes.
Railings are translucent or latticed elements, placed at the edges of the floor and terraces. Railings are placed as safety barricade on the sides of stairs, ladders, ramps, and escalators. These are placed to demarcate zones, to segregate movement channels, to regulate queuing people, as barricade for animals, and to prevent crawling infants and children from moving into unprotected areas. Railings are placed near wells, tanks and other water bodies. Railings are placed on inclined or slippery floors to prevent slip-fall. Railings are placed in vast grounds for people or groups to anchor themselves.
The chief element of railings, are top rail, and secondary elements are posts that support the rail and latticed in-fill panels. A rail can be defined as any long member, usually of round section, fixed to posts, for resting hands, or for grabbing as a support. Railings have a top rail or hand rail used for holding, and a foot rail and mid rails. The hand rail in a masonry structure is a wider ‘table’.
Masonry railings are often called parapets. In medieval castles, gapped parapets called crenellations or embrasures were formed to allow guns to fire through. On terraces and galleries of arid climates similar gaps are covered by pierced stones or metal lattice to allow the breeze to pass through at floor level of the terrace. This cooled the terraces faster, and provided comfort for occupants seating or sleeping on the floor. Latticed railing allows children to see through, and so discourage the climb-over.
Parapets are opaque structures, often designed as an upward extension of the wall. Classical design of a parapet em-battlement of a coping at the top and corbel below. The top of the parapet often slopes towards the enemy to enable the defenders to shoot downwards, and this incline is called the superior talus. Parapets are placed at roof or terrace edges, or on embankments. Opaque parapets are used for deflecting winds, provide privacy to floor level activities, add weight to the edge to prevent lift-off forces. Parapets serve, besides defence-offence, other purposes, such as: to shield a view, as a noise barrier, barriers against splashes of storm-water, missiles or flying objects. Edge beams are designed as parapets. Parapets that are small in size are called curbs. Curbs are used as dividers.
Fort walls have em-battlement parapets, which are pierced for styling, view beyond and for throwing defensive projectiles. Palaces and castles have decorative (non-defence) perforated parapets in various shapes such as circles, trefoils, quarter-foils.
The building act of 1707 in London and other towns of England banned the projected wooden eaves to prevent spread of fire along the wall, to the roof structure. A 18″ thick parapet was required and the roof edge was set back. The roof was set back little more to provide drainage of rain water. The parapet which was completely absent in earlier houses began to be treated by crenellation. (During medieval ages, provision of crenels required permission.) The parapet style was continued in Georgian houses giving an appearance of a flat edge roof. The parapets over the roofs were made taller, shaped, decorated and pierced.