Roofing in Norway

Norway's roofs have been shaped by a long, wet coastline, cold inland winters and an abundance of timber and stone. For most of its history the ordinary Norwegian house was a log building roofed with layers of birch bark held down by turf, while churches carried steep, tarred wooden shingles. From the 19th century, clay tiles, local slate and later sheet metal replaced turf in most of the country, but the turf roof never disappeared and is still built on cabins today.

Climate and hazards

Roofs must cope with heavy precipitation on the western coast, deep snow and frost inland and in the north, and strong winds along exposed shores. The long survival of medieval timber churches is credited to design that kept water off the structure: steep pitches that shed rain and snow, generous overhangs and wood-tar coatings. Turf roofs were designed to carry their own weight of roughly 250 kg/m² (about 51 lb/ft²), which could rise to 400-500 kg/m² (82-102 lb/ft²) with winter snow.

Roofing history

The oldest known dwellings were turf huts with a roughly circular plan in which roof and walls formed a single element of paired rafters meeting at a ridge, probably covered with hides over wooden poles. By about 1800 BC larger rectangular houses of about 70 m² (750 ft²) were being built at Gressbakken in the far north, though archaeologists are unsure whether their rafters rested on the stone-and-peat walls or on posts. Iron Age longhouses used rows of roof-bearing posts that divided the interior into three aisles.

Scandinavian roofs have probably been covered with birch bark and turf since prehistory. In the Viking Age and the Middle Ages most houses had turf roofs, while churches and buildings with steeper roofs were covered with boards, wooden shingles or lead. At least 250 wooden houses from before the Black Death (about 1350) survive, mostly log buildings, alongside the stave churches. Possibly more than 1,000 stave churches were built, mostly in the 12th and 13th centuries; about 150 still stood in the early 19th century, and 28 remain.

Stone and slate appeared on high-status buildings. A document by Bishop Arne from 1308 suggests that King Haakon's Hall in Bergen, built from the mid-13th century, was roofed with slate from Jondal in Hardanger, and evidence around Trondheim suggests slate was used as a building material from about 1100. In the late 17th century parts of Nidaros Cathedral in Trondheim received slate roofs from Klæbu, replacing wood and lead roofs lost in fires.

Fire shaped town building. After the fire of 1624, Christiania (now Oslo) was rebuilt as a fortified town under a building code that prohibited wooden houses. In the countryside turf stayed almost universal until the early 18th century and remained the most common roof on rural log houses until the late 19th century, when clay tiles, already used in towns and on manors, and corrugated iron spread outward. National Romanticism revived interest in turf just as it was disappearing.

In 1945, about 20,000 homes had been lost in northern Norway, 12,000 of them in Finnmark, and a competition that autumn sought prefabricated houses of up to 60 m² (650 ft²) for the rebuilding.

Traditional and vernacular roofs

• Torvtak (turf roof): sod laid over birch bark on gently sloping roof boards. The bark is the waterproof layer; six layers were considered adequate and up to 16 have been recorded. Turf pieces about 30 cm (12 in) square and 7.5 cm (3 in) thick were laid to a total of about 15 cm (6 in). About 30 years was a normal life before relaying. See torvtak.
• Stave church roofs: steep, stacked roofs of boards and wooden shingles, traditionally coated with wood tar. Urnes, built in the 12th and 13th centuries, has roof frames lined with boards and covered with shingles. See stave church roofs.
• Slate: phyllite slate from quarries such as those around Klæbu and Stjørdal near Trondheim was widely used for local and regional roofing from the 19th century.

Roofing today

Turf roofs are still widely used on new cabins, now laid over bitumen roofing felt and a dimpled drainage membrane rather than birch bark. Slate is still quarried: 2025 marked 150 years of production of Otta slate in Gudbrandsdalen, and a SINTEF study found older Otta slate roofs and façades still functional, noting that stone can far outlast the 60-year service life assumed in environmental product declarations. Housing form affects roof type: on 1 January 2008, 53.1% of Norway's 2,274,362 dwellings were in detached houses and 21.9% in multi-dwelling buildings.

Codes, standards and regulation

Building work is regulated under the Planning and Building Act and the technical regulations known as TEK17 (byggteknisk forskrift), administered by the Norwegian Building Authority (Direktoratet for byggkvalitet, DiBK), which publishes English translations.

Industry

Norway has a natural-stone roofing industry centred on phyllite slate, including Otta slate from the Pillarguri area south of Otta in Innlandet.

Notable roofs

• Urnes Stave Church, Luster: a UNESCO World Heritage Site, built in the 12th and 13th centuries using parts of an 11th-century church.
• Borgund Stave Church, Lærdal: the classic tiered shingle-roofed stave church.
• Røros, a UNESCO-listed copper-mining town of about 2,000 wooden one- and two-storey houses, rebuilt after Swedish troops destroyed it in 1679.
• Nidaros Cathedral, Trondheim, with its slate roofs.

Local roofing terms

• torvtak - turf roof
• skifer - slate

Sources and gaps

A national census of roofing materials, current market shares of tile, steel and membranes, and data on other domestic roofing manufacturers: published information is limited.