Dr. S. & S.S. GHANDHY GOERNMENT ENGINEERING COLLEGE SURAT. FLAT AND PITCHED ROOFS By: SUNIL ZALA(130230106062) Directed By: Ms. RAINA SHUKLA

Flat roofs

Flat Roof A flat roof is the most economical roof to build, but it adds little to the design of most houses. It requires a “built-up” or membrane roof covering.

Types of flat terraced roofing Mud terrace roofing Brick jelly or Madras terrace roofing Bengal terrace roofing Mud-Puska terracing with the tile paving Lime concrete terracing Lime concrete terracing with tile paving

Advantages of flat roof Design Typically the design of choice for smaller structures, such as garages and extensions, flat roofing consists of a horizontal base which is fixed to the ceiling joists underneath with a waterproof membrane applied on top. While flat roofs are designed to hold standing water to some degree, a slight pitch of only a few degrees is usually incorporated to enable rainwater to drain away into a hopper.

Materials Traditionally flat roofs have been constructed from asphalt or three- ply modified bitumen (also known as felt flat roofing) with a thin layer of gravel to protect the roof from the harmful effects of UV sunlight. A more recent and increasingly popular design is Ethylene Propylene Diene Monomer (EPDM), a 3mm thick rubber membrane which can be applied seamlessly in one piece and offers a lifespan of more than 40 years (compared to the 20 years for felt flat roofing). Cost Flat roofing is generally considered to be a more affordable option at the point of construction and involves considerably less materials and labour than a pitched roof. Full replacement of the roof, when the time comes, can usually be completed in a single day.

Disadvantages of flat roof Maintenance With a lifespan for a felt flat roof of only 20 years, the prospect of having to maintain and eventually replace this type of roof can be off-putting, especially if you are seeking to sell your home. While the extended lifespan of EPDM is a definite improvement on felt flat roofing, some regard it to be an unsightly alternative that may not be in keeping with the style and traditions of the adjoining property or neighbourhood.

The primary disadvantage to a flat porch roof relates to drainage or lack thereof. A flat roof can be designed to drain water moderately well. The more pronounced drainage problem occurs during winter, when snow sits until it melts. In some areas, that can be a mighty long time. The weight of snow means the porch has to be able to withstand a higher load of weight, which requires more involved engineering and greater material expense. For flat porch roofs that do develop a problem with “pooling” or “ponding” of water, expect it to deteriorate that much faster. Another drawback to the flat roof porch design is that if it does begin to leak from poor drainage, damage can result to the underside of the porch, including finished wood, decorated ceilings and even walls. Plus, you don't want to sit out on the porch on a rainy evening with a constant trickle of water down the neck of your shirt. It can not be used for industrial sheds without using intermediate columns. These roofs are not suitable where rainfall or snowfall is heavy. 

Pitched roofs 9

Types of pitched rooofs (a) Single rooofs (b) Doble or Purlin Roofs -Lean-to-roof -King post roof truss -Couple roof -Queen post roof truss -Couple-close roof -Scissor roof -Collar beam roof -North light roof truss -Mansard roof truss -Composite roof truss -Latticed roof truss

Advantages of pitched roof Loft Space Pitched roofs, which have at least two slopes that rise to meet at a peak, are constructed in such a way as to afford plenty of usable space in the loft area, either as much-needed storage or even as additional living space, such as a study or playroom. In the process of designing the roof, any planned usage of this area can be incorporated into the plans so this type of roof offers an unmatched flexibility that a flat roof cannot.

Lifespan The pitched roof, if constructed properly, is almost certain to offer a much longer lifespan than a flat roof, with materials that are more durable and weather resistant. The internal accommodation will be more efficiently insulated and will not suffer from the extremes of temperature that tend to afflict rooms under flat roofs. Installing a pitched roof also means the building can be more effectively blended in to either the rest of the property (in the case of an extension) or to neighbouring buildings, while also helping to retain a sense of individuality and character.

Disadvantages of pitched roof Expense Unfortunately one consequence of this is the increased expense, as the more complex design, additional building materials and extra man-hours cost significantly more than a flat roof. Foundations Pitched roofs also place a greater burden on the foundations of the building and this may have implications for the depth of the footings. Replacing a flat roof with a pitched roof on an existing structure is therefore not always feasible.

It has more weather effects It is not so durable. It can not be used for upper floor. The roof has leakage problem. When the roof is constructed with iron sheets, rusting problem may arise. The roof for offices etc. is costly as false ceiling is required for thermal comfort. 

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