Bangla Roof

The bangla roof (also called the Bengal roof or chala roof) is a roof with a curved ridge and eaves that droop down at the corners. It began as the everyday roof of village houses in the wet Bengal delta, now divided between Bangladesh and the Indian state of West Bengal, where roofs of straw, reed or grass thatch were bent into a curve over a light frame. From about the 16th century the shape was copied in brick and stone, first in Bengal and then in the palaces, mosques and pavilions of the Mughals and Rajputs across northern India.

From thatch to masonry

On a thatched hut, the curve helps rain run off quickly and away from the mud walls. Banglapedia's survey of Bengal temple architecture says the hut-style temples were modelled directly on thatched earthen huts, and that the curve, which works on a thatched roof, was kept in brick and terracotta purely for decoration. The Gangetic delta had little building stone, so temple builders worked in burnt brick and carved terracotta, imitating the bamboo frame and thatch in fired clay.

Types

Bengali builders named the forms by the number of roof slopes, chala meaning a roof surface:

• Do-chala ("two roofs"): two curved slopes meeting at a curved ridge, like a single village hut. Two do-chala units joined side by side make the jor-bangla ("twin bangla").
• Char-chala ("four roofs"): four curved triangular slopes meeting at a point, like a curved hip roof.
• At-chala ("eight roofs"): a char-chala with a smaller char-chala set on top to add height, giving eight roof surfaces in two tiers. Banglapedia says it became popular in the 18th and 19th centuries, especially in Hugli and Howrah.

A separate family of Bengal temples, the ratna type, adds towers (pinnacles) on top: five in a pancharatna, nine in a navaratna.

Dated examples

• Gunjanth Siva Temple, Jessore (Bangladesh): an at-chala temple of 1740.
• Kantanagar Temple, Dinajpur (Bangladesh): a navaratna temple begun in 1704 and completed in 1752. Its nine towers were lost in the earthquake of 1897.
• Rasmancha, Bishnupur (West Bengal): dated around 1600.

Spread beyond Bengal

The curved roof left Bengal in the 16th and 17th centuries. In the Agra Fort, the Khas Mahal, built about 1635 for Shah Jahan's daughters, has pavilions with Bengal-style roofs. The form also appears on the Moti Masjid in Delhi's Red Fort (1659), and later in Rajasthan, on havelis in Jaisalmer and Mandawa, on Jaisalmer chhatris of the 18th and 19th centuries and on the Hawa Mahal in Jaipur (1799). Nineteenth-century Sikh buildings, including the Harmandir Sahib in Amritsar, also use it.

Today

Village houses in Bangladesh and West Bengal are now more often roofed with corrugated metal sheets than with thatch, so the curved roof survives mainly in temples, mosques, and heritage buildings, and in new buildings that deliberately borrow it.