Roofing in Iran

Iran has one of the richest masonry roofing traditions in the world. On the arid Iranian plateau, where timber was always scarce, builders roofed spaces with vaults and domes of mud brick and baked brick, and developed rooftop windcatchers and domed ice houses to manage heat without power. The humid Caspian provinces, by contrast, have a tradition of pitched roofs.

Climate and hazards

• Plateau and deserts: hot, dry summers, cold nights and low rainfall across the central plateau and the Dasht-e Kavir and Dasht-e Lut deserts. Clear, dry winter nights allow heat to radiate to the sky, which made ice-making possible.
• North-west: cold winters, which discouraged open courtyards in some buildings.
• Caspian coast: heavy rain and humidity, hence pitched roofs.
• Earthquakes: seismic risk is high. Heavy earth roofs on older buildings, and poorly connected timber roof beams on rural masonry houses, are known vulnerabilities.

Roofing history

Ancient earth building. Moulding and sun-drying mud into bricks has been practised in Iran since ancient times and never fully abandoned. Records of yakhchāl ice houses go back to about 400 BC.

Sasanian. The Sasanian Empire built the first large-scale domes in Iran, together with massive barrel-vaulted halls; the great brick vault of Taq Kasra at Ctesiphon, in present-day Iraq, is the best-known survivor (see taq-kasra).

Islamic era. Builders developed tall and complex domes, including double-shell domes in which a tall outer dome is separated from a lower inner one; the Shah Mosque in Isfahan has about 14 m (46 ft) between its two shells. The Dome of Soltaniyeh, about 50 m (164 ft) tall and 25 m (82 ft) across, is one of the largest masonry domes ever built. Squinches and muqarnas handle the transition from square rooms to round domes, and Persian domes are known for exterior cladding in coloured glazed tile.

Modern. Most new buildings are reinforced concrete or steel frame with flat roofs waterproofed with bituminous membranes, often finished with tiles or insulation.

Traditional and vernacular roofs

• Earth vaults and domes: in desert cities such as Yazd, a UNESCO World Heritage site, earth is used for walls and roofs, and roofs are formed as vaults and domes.
• Badgir (windcatcher): towers that catch the prevailing wind and vent warm air. Yazd's windcatchers are typically four- or eight-sided, and the tallest Iranian examples reach about 34 m (112 ft). See badgir.
• Yakhchāl: a tall domed ice house, built of water-resistant sarooj mortar (sand, clay, lime, ash, goat hair and egg white) with walls at least 2 m (6.5 ft) thick at the base, over storage of up to about 5,000 m³ (180,000 cu ft). The Kerman yakhchāl is about 18 m (59 ft) high. See yakhchal.
• Ab anbar: domed water cisterns, often ventilated by windcatchers, still common in the countryside.
• Caspian pitched roofs: steeper roofs suited to heavy rain.
• Rural confined masonry: in many rural single-family houses, timber roof beams sit on concrete tie beams over brick walls; the World Housing Encyclopedia identifies weak beam-to-tie-beam connections as a seismic deficiency and recommends anchoring the beams.

Roofing today

Reinforced concrete and steel frames with flat, membrane-waterproofed roofs are standard in cities.

Codes, standards and regulation

Seismic design is governed by the Iranian Code of Practice for Seismic Resistant Design of Buildings, Standard No. 2800 (an English version of the third edition, dated 2007, is published through Japan's IISEE world list of seismic codes).

Notable roofs

• Dome of Soltaniyeh: about 50 m (164 ft) tall.
• Shah Mosque, Isfahan: double-shell dome.
• Historic City of Yazd (UNESCO): earthen vaults, domes and windcatchers.
• Kerman yakhchāl: well-preserved conical ice house.

Local roofing terms

• badgir - windcatcher
• yakhchāl - "ice pit", domed ice house
• ab anbar - domed water cistern
• sarooj - traditional water-resistant mortar
• muqarnas - stalactite-like vaulting used in dome transitions

Sources and gaps

Figures on current roofing materials, national regulations beyond Standard 2800 and information on the roofing industry: published information is limited.