A metal roof is Finland's most popular roofing material — approximately 70 per cent of all new roofs are made of sheet metal. The material owes its popularity to its affordability, light weight and long service life. A metal roof is suitable for virtually all roof pitches and building types, from detached houses to terraced houses and industrial properties. A modern metal roof is manufactured from hot-dip galvanised steel sheet coated with polyester, polyurethane or PVC. The coating protects the sheet metal from corrosion and UV radiation. There are significant differences in durability between coatings: basic polyester lasts approximately 20–30 years, whereas a PVC coating can maintain its appearance for up to 50 years. Metal roof installation requires professional expertise, as incorrectly fastened sheet metal can cause leaks and noise problems. In Finland, metal roof installation is governed by, among other things, the RT card guidelines and roof safety regulations.
Types and materials of metal roofs
Metal roofs are divided into profiled metal roofs and standing seam roofs. A profiled metal roof is the more affordable option, in which the metal sheets are formed into a corrugated or trapezoidal profile. A standing seam roof has a flat surface and the seams are machine-crimped to form a watertight seal, making it more aesthetically pleasing and waterproof.
The most commonly used base material is 0.5–0.6 mm steel sheet, hot-dip galvanised (275 g/m²). Aluminium sheet is used in special applications, such as coastal construction, where salt air corrodes steel. Aluminium is more expensive but does not rust.
The colour range for metal roofs is extensive. The most popular shades are dark brown (RR32), brick red (RR750) and black (RR33). When choosing a colour, local planning regulations should be considered — in many municipalities the roofing material and colour are predetermined.
Metal roof installation and fastening
Metal roof installation begins with installing the roofing underlayment and batten lathing. The underlayment is a waterproof layer that protects the structure from potential condensation water. The battens serve as the fastening base for the metal sheets, and their spacing depends on the roof profile type — typically 350–400 mm centre-to-centre.
Metal sheets are fastened with screws to the battens. Typically 6–8 fastening screws per m² are required. The screws must be fitted with EPDM rubber washers to ensure the fastening point remains watertight. Incorrect screws are one of the most common causes of metal roof leaks.
The flashings at penetrations, the ridge and the eaves are critical points where unskilled work easily leads to leaks. The RT 85-11163 guideline card provides detailed instructions for metal roofing installation and details. Installation work should always be carried out by an experienced roofing contractor.
Durability and maintenance
The service life of a properly installed metal roof is 40–60 years depending on the coating. Regular maintenance extends the roof's service life; this includes removing debris and leaves, cleaning eaves gutters and checking fastening screws.
The most common problems with metal roofs are rusting at fastening points, leaking at seam or joint locations, and sheets loosening in the wind. Coating damage must be repaired immediately, as exposed steel begins to rust rapidly in Finland's humid climate.
Maintenance painting significantly extends the service life of a metal roof. Painting is typically carried out every 15–25 years with acrylic or polyurethane paint. The cost of maintenance painting is approximately 8–15 €/m², whereas a completely new metal roof costs 35–65 €/m² installed.
Metal roofs in Finnish conditions
Finland's climate places special demands on metal roofs. The weight of snow and ice can load the roof significantly — the snow load in the north can be as much as 3.5 kN/m². The advantage of a metal roof is its slippery surface, from which snow slides off more easily than from a tile roof, for example, which reduces the snow load but necessitates the installation of snow guards for safety reasons.
In cold climates, the thermal expansion of sheet metal is a significant factor. Long metal sheets can move several centimetres with temperature fluctuations (-30°C to +60°C). This must be taken into account in fastening — sliding clips and correctly dimensioned seams are essential.
Noise problems are the best-known weakness of a metal roof. Rain and hail make a loud noise on a metal roof, which carries into the interior, especially in attic rooms. The problem is solved with adequate insulation and underlayment selection — in modern metal roof solutions, noise is no longer a significant nuisance.
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Updated: April 2026
