The cladding of the Helsinki Olympic Stadium will be rebuild by Siparila, a company renown for its woodworking skills. This national monument of historic value will be restored to its original splendour as closely as possible. The cladding will be finished by the end of next year.
In the course of the restoration, the wood cladding will be modelled on the original design except that it will be extended two meters upwards to conceal the new stadium canopies.
Challenges posed by the curved inclined exterior
Structurally, the higher-than-before wooden exterior will be implemented using a separate supportive lattice to which the frame and wood cladding will be fixed. The biggest challenge in the project is the complex form of the exterior in which the walls tilt outward especially at the ends.
“No doubt this is the toughest project we’ve ever tackled. Special attention needs to be paid to dimensions and framework details. Even a minor deviation at a single point is multiplied as you proceed outward,” says Chief Sales Officer Olli Prättälä of Siparila explaining the challenges they are facing.
On-site safety is another challenge because the installations are carried out at elevated levels. Since it is not possible to construct scaffolding, the installers carry out their work using boom lifts and aerial work platforms. Because of safety considerations, the area underneath the platforms is off limits for other on-site workers.
Smartly new – with due respect for the old
The wood cladding of the Olympic Stadium will be re-created following the original design as closely as possible. At the tendering stage, Siparila supplied a total of nine test walls of different shades and finishes which were then installed on the south end of the Olympic Stadium exposed to the action of weather for two months. The tests showed that the finish satisfied stringent quality requirements. The width of the panels supplied by Siparila was slightly adjusted to match the original.
“It’s fair to say that this was no run-of-the-mill job, it was like walking on eggshells. The project called for true craftsmanship and forward thinking – you need to keep the subsequent work operations in mind all the time because any errors are multiplied in the course of the work,” Prättälä says.
The external cladding of the Olympic Stadium will consist of Finnish PEFC-certified fine-sawn spruce. The finely textured surface provides better adhesion for paint than an unfinished coarse surface, which gives it enhanced weather resistance in harsh conditions. All in all, the external cladding covers an area of 9,000 m2 with the total quantity of spruce reaching 500 m3. Theoretically, the wood cladding of the Olympic Stadium will trap up to 500 tonnes of carbon dioxide over its service life. The cladding panels are finished in an industrial process under controlled conditions. The final coat of paint will be brush-applied to the installed cladding next summer as required by the painting certificate.
Currently, a total of seven professionals are working on the external cladding. To date, framework construction and external cladding have proceeded up to the first corner. When the Helsinki Olympic Stadium is re-opened at the end of 2019, it will look practically the same as at the end of the 1952 Olympic Games.