Scandinavian Sod Roofs

A sod roof, or turf roof, is a roof covered with grass turf laid over a waterproof layer of birch bark on a timber deck. It is known in Norwegian and Swedish as torvtak, in Danish as tørvetag and in Icelandic as torfþak. For centuries it was the standard roof of rural log houses in Norway and large parts of Scandinavia.

How it works

Birch bark, laid in overlapping layers, is the actual waterproof membrane; it is naturally resistant to rot and can last for generations. The turf above holds the bark in place, protects it from sunlight and wind, and adds insulation. Around 30 years was regarded as the normal life of a sod roof in most places before re-laying.

History

Scandinavian roofs have probably been covered with birch bark and sod since prehistory. In the Viking Age and Middle Ages most houses had sod roofs, while churches and buildings with steeper roofs used boards, wooden shingles or lead. In rural areas sod roofs remained almost universal until the early 18th century. Their distribution closely follows the log-building tradition of Finland and the Scandinavian peninsula.

Decline

Tile roofs, already common in towns and on manors, gradually replaced sod roofs in the countryside during the 19th century, except in remote inland areas. Corrugated iron and other industrial materials added to the pressure. Sources differ on timing: some date the main decline to the 18th century, others to the late 19th century.

Revival

Just as the tradition was disappearing, the national romantic movement revived interest in vernacular building. Demand from mountain lodges and holiday cabins, open-air museums and preservation societies kept the skills alive. Turf roofs are still widely used on new cabins in Norway, and they have reappeared as an alternative to modern materials.

Elsewhere

Turf roofs are also traditional on farm buildings in Iceland, and similar earth-covered roofs exist in other cold or treeless regions.