Do you feel flat roofs are too common, making the building look like a box? Often, they also have been hot boxes, leaking during rains. Sloping RCC roofs are fine, but we need to finish with tiles on top, creating a double roof, unnecessarily spending extra money. Since the sloping roof rises along the length, the longer the room, higher goes the roof height. There are many houses with an externally impressive sloping roof but internally appearing so much out of scale that the architects are forced to suggest a loft up there, often only to make the height bearable.
Given this scenario, roofs with one-way curve, like the segment of a circle, help in many ways. Even if we start at the lowest end at nine ft., we can restrict the height at the higher end to reasonable limits by gently curving up and then going generally flat where the roof meets the wall. This solution where we can get a roof seemingly curved in front and flat behind is mainly for large spans, so all smaller rooms can anyway get fully curved looks.
Orientation matters
Besides modulating the height, there are also passive cooling benefits. The amount of heat getting conducted into the building depends upon the angle of sun rays where the direct rays conduct more heat and angular sun rays tend to reflect back to the sky, hence have lesser conduction. Solar heat is the strongest from 10 a.m. to 3 p.m., being cooler before and after these hours, thanks to the low sun position. Depending upon the orientation of the sloping roofs, facing north or west, they can be designed to receive varied degrees of heat, but often the design context may not permit us to slope the roofs anyway we want.
Maximum heat transmission happens in flat roofs which get direct rays for the longest hours compared to the other forms.
It's here that the curved roofs score over the others, getting direct sun rays for the least hours. Only a small part of the curve at any given time would be subjected to direct solar light and heat, other gradually curving surfaces receiving the light at oblique angles, hence receive less heat, leading to differences between outdoor and indoor surface temperatures.
Tiled looks
Visibility from the road side is among the reasons people prefer to have sloping roofs, with a desire for tiled looks. While we get to see the tiles from afar, as we come closer to enter the gates of the building, we see the lowest edge of slope as a straight line only, disappointing both the owners and the visitors.
With the roof curving, the curved profile is visible wherever we are, unless we stand under it. This contribution to aesthetics compliments other design criteria, in favour of choosing curved roofs.
(The writer is an architect, working for eco-friendly designs and can be contacted atvaranashi@gmail.com)
