korkokattorajotus

Korkokattorajotus is a Finnish construction method used primarily in residential and light commercial buildings to strengthen or modify roof structures. The term derives from the Finnish words “korko” (height), “kattori” (lightweight wooden beam or rafter), and “-jaton” indicating an action of alteration. Practically, the technique involves adding additional longitudinal members or infill panels to existing roof rafters to increase their load‑bearing capacity, correct deflection, or accommodate new roofing materials.

The process typically begins with a structural assessment carried out by a licensed engineer. Once a need for reinforcement is confirmed, the existing rafters are inspected for rot, insect damage or previous modifications. Additional wooden or composite elements are then precisely cut to match the roof’s geometry. These new components are fastened to the original rafters through metal brackets, screws, or adhesives, ensuring a continuous load path. In many cases, the added members are fabricated from plywood or engineered lumber because of their high strength‑to‑weight ratio.

Korkokattorajotus offers several advantages. By reinforcing the rafters, it allows for higher roof pitches or the installation of heavier insulation and solar panels without compromising structural integrity. It can also extend the life of older roofs that have deteriorated over time, reducing the need for complete roof replacement. However, the method does require careful design to avoid creating new weaknesses or moisture problems, especially in climates with high precipitation.

In Finland, the technique is regulated by the Finnish Building Code, which stipulates minimum load requirements and permissible materials. Contractors performing korkokattorajotus must maintain documentation of design calculations and seasonal testing records. The practice is gaining popularity as homeowners and architects seek cost‑effective ways to upgrade roof performance without major reconstruction.