Roofing in Bhutan

Bhutan is a small Himalayan kingdom whose roofs are unusually tightly bound up with national identity. The traditional roof is a broad, low-pitched roof of loose pine shingles held down by stones, lifted on timber above the walls so that an open, airy loft is left beneath it. Corrugated iron has replaced the shingles on almost all dzongs and on many other buildings, but the shape of the roof is protected by law: since 1998 every building in the country must have a sloping roof.

Climate and hazards

Bhutan rises from subtropical foothills on the Indian border to high Himalayan peaks. The monsoon brings heavy summer rain, valleys are swept by strong winter winds, and the country lies in the seismically active eastern Himalaya. Its dense forests have long supplied abundant timber, and Bhutanese building is correspondingly timber-centred, which also makes it vulnerable to fire and decay.

Roofing history

Bhutan's great fortress-monasteries, the dzongs, reached their peak of development in the 17th century, and large manor houses appeared from the late 19th century. Both used the same roofing principle as farmhouses: a timber roof frame of hardwood and bamboo, joined without nails, open at the eaves and covered with timber shingles weighted with stones. Buddhist temples (lhakhang) were often crowned with gilded copper roofs.

In modern times corrugated galvanised iron sheet has replaced timber shingles, so that almost all dzong roofs are now metal. Trongsa (Tongsa) Dzong retains one of the few surviving shingle roofs, which was being restored in 2006-07. In more recent years metal shingles have become popular for their durability.

Traditional and vernacular roofs

The Bhutanese shingle roof has these main features:

• Covering: loose pine shingles laid on the frame and held in place by laths with stones placed on them at regular intervals, a design able to survive severe winter winds.
• Frame: hardwood and bamboo, assembled without nails or iron, with a decorated timber cornice and no rain gutters.
• Open loft: a large ventilated gap between the top of the walls and the roof, used for storing and drying chillies and animal skins and insulated with bamboo mats and hay. The raised roof gives the "flying roof" appearance typical of Bhutanese houses.

A preserved example is the mid-18th-century farmhouse that houses the Folk Heritage Museum in Thimphu.

Roofing today

Corrugated galvanised iron now covers almost all dzong roofs, and metal shingles are increasingly used.

Codes, standards and regulation

A royal decree of 1998 requires all buildings to have sloping roofs, together with multi-coloured timber fronts and small arched windows. The traditional code of conduct and design known as Driglam Namzha sets out rules for dzongs and ordinary buildings. Traditional construction does not use nails or iron bars.

Notable roofs

• Trongsa Dzong: one of the few dzongs still with a shingle roof.
• Folk Heritage Museum, Thimphu: a mid-18th-century farmhouse with a stone-weighted pine-shingle roof.
• Lhakhangs (temples) with gilded copper roofs.

Local roofing terms

• dzong: fortress-monastery
• lhakhang: temple
• Driglam Namzha: traditional code of etiquette and building

Sources and gaps

Information on modern roofing materials, statistics, building codes and domestic roofing manufacturers in Bhutan: published information is limited.