Flat Roof : Types, Advantages & Disadvantages
A roof laid at an angle of under 10° to the event is known as flat roof. Flat roof might be of reinforced cement concrete, reinforced brick work, precast concrete with channel units, waffle units and so forth, flagstones bolstered on rolled steel joists or jack curve type.
The most significant prerequisite of flat roof is proficient waterproofing and roof drainage. The roof surface has in this manner to be furnished with appropriate waterproofing treatment and essential slants to fulfill these prerequisites.
Likewise a layer of protecting material (mud, lime, concrete) is laid over the roof surface to give satisfactory warm protection to the space beneath. This space is known as terracing or grading.
A specific slant can be given to the roof by changing the thickness of the terracing material or the roof piece can be developed in slant. In circumstances where warm protection isn't fundamental, the slant for drainage of the roof is given in the roof section itself and the roof surface is given satisfactory water proofing treatment by utilizing bitumen felts and so on.
In places where the terraced roof is to be utilized for open air living, the top surface of the terracing ought to be made impervious to wear other than making arrangements for effective waterproofing and drainage for the roof.
Pros and cons of Terrace Roofing
Points of interest of Flat Roof
1. The development of flat roofs is streamlined and support is simple.
2. The roof can be utilized as a terrace for playing, planting, resting and for praising capacities.
3. It is simpler to make the flat roof flame resistant than a slanting roof.
4. They maintain a strategic distance from the walled area of the triangular space. This improves the design appearance of the structure.
5. Flat roofs have better protecting properties and they are increasingly steady against high breezes.
6. The development work of upper floors can be effectively begun. If there should be an occurrence of a pitched roof, the whole roof is to be evacuated and is to be supplanted by another roof under such conditions. It is accordingly viewed as the most ideal decision for multi-storeyed structures.
7. They don't require bogus roofs, which is fundamental in pitched roofs.
8. Flat roofs end up being by and large conservative.
Impediments of Flat Roof
a. Transitional sections in flat roofs give them a free hand during the development of the range.
b. Self load of roof is more. Because of this, the extents of bars, sections and other auxiliary individuals are overwhelming.
c. Flat roofs are presented to the sun and are exposed to rough temperature changes which may prompt splits in the outside of the roof.
d. The pockets of water are framed on the outside of the roof, if slant isn't adequate. This prompts the spillage of the roof and it here and there ends up being hard to precisely find the situation of the spillage on the roof.
e. They are inadmissible at the spots of overwhelming precipitation, uneven regions or zones where there is substantial snowfall.
f. The dead weight of a flat roof is significant and henceforth it ends up being progressively costly. It's underlying expense is higher than a pitched roof.
g. The advancement of work in a flat roof is delayed when contrasted with that of a pitched roof.
h. The underlying expense of a flat roof is additionally more than the pitched roof.
i. Working with the flat roof is altogether presented to the enduring conditions, yet the anticipating components, for example, overhang of the pitched roof gives some assurance to the structure.
Types of Flat Roofs
1. Mud Terrace Roofing
2. Brick Jelly or Madras Terrace Roofing
3. Bengal Terrace Roofing
This kind of terracing is reasonable where precipitation is less. It may very well be given either on tiles or on wood sheets. In both the cases, terracing is made with white earth mud containing an enormous level of sodium salt.
The mud-terracing in Punjab is given over roof which comprises 50 mm x 50 mm x 6 mm T-segments divided at 32 cm place to focus over R.S.J. all around consumed tiles of size 30 cm x 30 cm x 5 cm or 30 cm x 15 cm x 5 cm are set between the spines of the T-areas utilizing lime mortar. Over the tiles, a 15 cm thick layer of hardened mud, white in shading and containing sodium salts is spread and beaten with sticks till the surface turns out to be hard and the mixer bounces back. The surface is then plastered with mud and cow excrement blend plaster. At long last, the surface is done with 1 : 4 cement-cow dung plaster.
In Maharashtra and Madhya Pradesh practice, mud terracing is done on teak wood sheets (4 to 5 cm thick) nailed to the wooden joists. On the sheets, a 2.5 cm thick layer of wood shaving is spread over which bricks are laid tense in lime or mud mortar.
Brick Jelly Roofing or Madras Terrace Roofing
The teakwood wood joists are set on rolled steel joists with a furring piece between the joists and rolled steel joists. The furring is put slanting and it gives fundamental incline to the flat roof. A course of exceptionally arranged terrace bricks is laid slantingly over the joists.
The size of the bricks is commonly 150 mm x 75 mm x 25 mm and they are put in lime mortar. After the brick course has set, a course of brick bat concrete is laid. The thickness of this course is around 75 mm and it comprises 3 pieces of brickbats, one piece of rock and sand and half of lime mortar by volume.
The outside of the roof is done by three layers of plaster. The surface is then scoured and cleaned and given an incline of 1 out of 30. As the kind of flat roof development is generally utilized in old madras state, it is known as madras terrace roof.
Bengal Terrace Roofing
The roof is commonly utilized in Bengal to cover verandah and henceforth it is normally known as Bengal terrace roofing. The rafters are put in position, inclining outward from the fundamental divider at a separating of 30 to 50 cm community-to-focus. One finish of the crossbeam is embedded into the principle divider for a length of 20 cm and their opposite end is fixed on a verandah divider plate or bressummers.
The boards or reapers are fixed to the upper surface of the rafters at right angles and are dispersed at 15 cm habitats. On the boards, a course of flat tiles all around absorbed white wash is laid in lime or cement mortar.