VIEWS: 3 PAGES: 11 POSTED ON: 11/15/2012
Guided By - Ar. Sandeep Mishra Submitted by – Akshat Garg , Alok Kumar Maurya, Ankita Manglik , Komal Yadav , Nitya Singh B. Arch. IV Yr. Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. A Roof is the covering on the uppermost part of a building. A roof basically consist of roof covering materials supported on structural elements installed on building top. The structural elements may be trusses, portals, flat slab, shell, dome or space frame. Whereas the roof covering material may be thatch, wooden shingle , tiles, slates, A.C. sheets , G.I. sheets etc. A well planned roof should be – Structurally sound. Durable against adverse effects of elements like rain ,snow, sun ,wind. Efficient water proofing & drainage systems. Provide desirable insulation against heat & sound. Reasonably priced. Aesthetically attractive History of roof coverings – The earliest roof used readily available materials from the surrounding terrain and needed to be portable. Most likely the first roof was covered with dirt, underlayed with branches and supported by wooden beams. The Sod Roof system is one the original "Green Roofs" and one of the oldest flat roofing systems know. Dirt roofs might be the oldest flat roofs ever made. Although Sod Roofs are ancient in design, early American settlers in the Great Plains used this design in the 1800's. Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Over 30,000 years ago, Aborigines used bark from birch trees for their roofs. But in places like Siberia where birch trees were not available, hunter gathers used mammoth skins to cover their dwellings. Mamoth Skins are one of the oldest roofing materials known to mankind. The whale skin huts would have been similar in design. More advanced civilizations used thatch and reeds to build dwelling roofs. The dwellings were more permanent structures but were designed to be easily dismantled because of spring floods. Later these dwellings became permanent when built on piled or rock foundations. The Thatch Roof dates back to around 30,000 BC. This style of roof is still being used in parts of Africa where climates although for use of such housing Natural asphalt was first used as early as 30,000 BC as a waterproofing technique, something that is still used today. Ceramic tiles, another familiar roofing product, was created around 10,000 BC by the Chinese and shortly after in the Middle East. Clay Tile roofs are the oldest roofing product to still be used today. The Chinese developed Clay baked tiles around 10,000 BC. Shortly after Clay Tiles were produced in the Middle East. Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Classification of roofs – 1) Flat or Terraced Roof 2) Pitched or Sloped Roof 3) Flat roof – Properties - 1) A roof is designated as flat id its slope is less than ten degrees. 2) Flat roofs have traditionally been used in hot climates where water accumulation is not a problem. 3) They were generally unkown in northern climated before the end of the last century. Advantages of flat roof : 1) No space lost below roof, i.e. no dead space 2) Less material is used than in a sloped roof 3) The rooftop is potentially useful as a terrace, or sleeping porch 4) Potentially pleasing appearance 5) Easier to build than a sloped roof Disadvantages of flat roof : 1) Roof elements can not overlap, hence waterproofing must be more complex, and more thorough 2) Drainage is not automatic 3) Support of snow load must be insured Pitched roof – it is the cheapest alternative for covering the structure. This is generally constructed in wood or steel The pitch is the angle at which the roof rises from its lowest to highest point. Most domestic architecture, except in very dry regions, has roofs which are sloped, or pitched. example thatch, require a steep pitch in order to be waterproof and durable. Other types of roofing, for example pantiles, are unstable on a steeply pitched roof but provide excellent weather protection at a relatively low angle. Advantages – These are light in weight. It can be used for long span without introduction of the intermediate supports. Drainage is automatic. Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Leakages can be easily detected. These roofs are preferable in heavy rainfall and snowfall area. Easy to install and rapid in construction as there is no need of formwork. Disadvantages – Noisy Thermal insulation is not better as of flat roof. Roof top is not accessible. It cannot resist heavy wind pressure. Being softer these sheet are more likely to tear away in heavy storm. Having greater thermal expansion results in noisy creaks and more stress on fasteners. It cannot be used in multi-storied buildings. Parts of a roof There are two parts to a roof, its supporting structure and uppermost weatherproof layer. In a minority of buildings, the outer layer is also a self-supporting structure. The elements in the design of a roof are :- the material the construction the durability The material of a roof may range from banana leaves, wheaten straw or seagrass to lamininated glass, aluminium sheeting and precast concrete. In many parts of the world ceramic tiles have been the predominant roofing material for centuries. The construction of a roof is determined by its method of support and how the underneath space is bridged and whether or not the roof is pitched. In regions where there is little rain, an almost flat roof with a slight run-off provides adequate protection against an occasional downpour. The durability of a roof is a matter of concern because the roof is often the least accessible part of a building for purposes of repair and renewal, while its damage or destruction can have serious effects. Roof covering material – There are an enormous variety of roofing materials, selection is based on price, durability, appearance, roof slope For pitched roofs: Wood Asphalt shingles Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Slate Tile Metal Asphalt shingle - There are two kinds of asphalt shingles on the market: Fiberglass shingles and organic-mat shingles. Fiberglass shingles are thinner, lighter, easier to lug around, and carry a better fire rating than organic shingles. Organic-mat shingles are tougher and stay more flexible in cold weather. Fiberglass shingles predominate in southern and central regions, but organic shingles are still popular in the North and are almost the universal choice in Canada. In practice, organic shingles have a much higher tear strength and nail-pull resistance than fiberglass shingles. Asphalt shingles composed of o Felt or fiberglass substrate, impregnated with asphalt o Mineral surface sprayed on surface o Adhesive seal-down strips at midpoint. o Multiple layers in architectural (built-up) shingles Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Asphalt shingles Properties - Asphalt shingles are an economical versatile roofing solution. They're relatively inexpensive to buy and install, are suited to roof pitches from 4-in-12 to vertical. available across a wide range of quality, cost, and style. Easy to cut, fit, and fasten, asphalt shingles are compatible with many different kinds of flashing and edging products. They don't require specialized accessories for roof edges, wall terminations, chimney or vent Shingle must resist abrasion from elements, degradation from UV, loss of asphalt due to drying (heat), etc. Shingles carry warranties of 15 to 40 years depending on the amount of material used to make the shingle. Weight per square varies accordingly. Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Wood shakes and shingles Shakes are rough surface (hand split or similar) and provide heavy shadow lines Shingles are sawn and are used for siding as well as roofing Cedar shingles are the most common, they are expensive and must be treated with fire retardant Slate- A very long-lasting roof, and quite expensive. Roof framing must be reinforced for the weight Slate should not be walked on if old Can be repaired with clip, normally fastened with copper nails in pre- drilled holes Tiles – Clay and Cement tiles used very commonly in warmer climates. Roof framing must be reinforced Applied with mortar or using nails Traditionally applied over purlins, nailed to sheathing today Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Metal roofing Recent improvements in paint quality and life have brought more painted steel roofs into the residential market. Cost competitive with asphalt shingles, and longer lasting, used commonly for agricultural structures Attached with gasketed nails or more commonly with gasketed screws Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. For low slope and flat roofs Roll roofing Membrane Built-up Roll roofing traditionally used for low-slope residential work. Available in single and double coverage. Very inexpensive, but considered unattractive Applied with nails and tar, tar typically leaks out at edges Membrane roofing “Rubber” roofing (EPDM) and other similar materials come in sheets or rolls, are glued or ballasted to the roof, and seams are heat or solvent welded. Materials are relatively expensive, but roof is long lasting and stays flexible. Built-up roofing – multiple layers of felt and tar applied to a roof deck, and then the surface is covered with ballast. Labor intensive, nasty materials, and dangerous work, but it used to be the only way to get a waterproof flat roof Department of Architecture, B.B.D.N.I.T.M., LUCKNOW. Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
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