Roofing in Finland

Finland's building tradition is one of log construction in a boreal forest, and its roofs followed suit: birch bark weighed down with poles, boards, turf and, later, tarred wooden shingles. Tar from Finnish pine forests was a major export for centuries. In the 20th century functionalist architects introduced flat roofs, and today profiled and seamed steel sheet is a very common covering on Finnish houses.

Climate and hazards

Roofs must carry heavy snow for long winters, especially in the east and north, and survive frost and freeze-thaw. Fire repeatedly destroyed wooden towns: on average a Finnish wooden town burned every 30-40 years, and Oulu suffered fires in 1822 and 1824. After the great fire of Turku in 1827, Turku Cathedral was largely rebuilt in brick.

Roofing history

Corner-timbered log construction has been common across the northern boreal zone since prehistoric times. The simplest Finnish building was the kota, a conical or tent-like dwelling covered with fabric, peat, moss or timber and still used by the Sámi in Lapland. The basic rectangular log building had a low-pitched saddle-back roof.

Tar was first produced in the Nordic countries during the Iron Age and was used above all to seal wooden boats. Large-scale tar production began in Finland in the early 17th century, when the country was part of Sweden, and by the late 17th century tar was the third most valuable export of the Swedish realm. Using tar on roof shingles is a later application of the same product.

Until the early 19th century the traditional Finnish roof was the malkakatto: wooden slats covered with several layers of birch bark, held down by long timber poles weighted with boulders, all left unpainted. Wooden shingles are a comparatively recent import, arriving in the early 19th century. Wooden churches of the 17th and 18th centuries, such as the Lapp Church at Sodankylä (about 1689) and Petäjävesi (1763-1765), show the steep saddle-back roofs of the period.

Functionalism brought the flat roof. Alvar Aalto's Paimio Sanatorium (completed 1933) used flat roofs with reinforced concrete and strip windows, and a 1931 co-operative office in Rauma had a roof terrace. After the Second World War, standard-design wooden houses for veterans (rintamamiestalo) were built in large numbers, and over 500 wooden houses of this type were delivered to the Soviet Union as war reparations between 1944 and 1948.

Traditional and vernacular roofs

• Malkakatto: birch-bark roof weighted with poles and stones. See birch-bark roofing.
• Turf roofs: used on log buildings across Finland and the Scandinavian peninsula, following the distribution of log construction.
• Shingle roofs: thin wooden shingles, introduced in the early 19th century and today often coated with tar.
• Sauna and riihi: early smoke saunas had no chimney; rocks were heated by burning wood for 6-8 hours and the smoke let out through a hatch. The threshing-drying barn (riihi) was another smoke-filled log building of the farm.

Roofing today

Steel sheet in tile-profile and standing-seam forms is a very common roof on Finnish detached houses; at the 2023 Loviisa housing fair, almost all the exhibition houses had steel roofs. Concrete and clay tiles, bitumen felt and bitumen shingles are also used, and apartment and commercial buildings mostly have flat or low-slope membrane roofs.

Codes, standards and regulation

Building requirements have been set by the Ministry of the Environment in the National Building Code of Finland (Suomen rakentamismääräyskokoelma), with structural loads including snow following the Eurocodes (Eurocode 1, Part 1-3 for snow).

Industry

• Ruukki, the roofing and construction brand of Rautaruukki, founded by the Finnish state in 1960 and owned by SSAB since 2014, is a major producer of steel roofing in Finland and abroad. See Ruukki.
• The Nordic membrane group Nordic Waterproofing operates in Finland. See Nordic Waterproofing.

Notable roofs

• Petäjävesi Old Church (1763-1765), built by master builder Jaakko Leppänen, a UNESCO World Heritage Site with a steep roof recalling the Gothic tradition and a 13 m (43 ft) wooden vault inside.
• Kärsämäki Shingle Church (1999-2004), designed by Anssi Lassila using 18th-century timber techniques and a shingle-clad exterior.
• Paimio Sanatorium (1933), an early functionalist flat-roofed building.

Local roofing terms

• malkakatto - birch-bark roof held down by poles
• kota - Sámi/Finnish hut covered with fabric, peat, moss or timber
• riihi - threshing-drying barn
• rintamamiestalo - post-war veterans' house

Sources and gaps

Market shares for Finnish roofing materials were not found in official statistics; the observation on steel roofs at the 2023 Loviisa housing fair comes from a manufacturer's report.