Høyt Under Taket was able to achieve the project requirements in part because of a cooperative, flexible design team that was passionate about mass timber and coming up with innovative solutions. Sondre Dolsvåg, an engineer at Degree of Freedom, was in charge of structural engineering, while Bård Stangnes, Senior Architect & Project Leader at Snøhetta, oversaw architecture. Sondre was also an avid climber, which was helpful for a project he calls a “perfect fit.”
The Sylva CLT Rib was crucial for the eye-catching and functional result, especially in areas with long spans. Frames were used to create a ‘cave feeling’ in the main hall, limiting spans to six meters in most parts of the building. Solid CLT frames integrated well into the building design.The exception to the six-metre ceiling spans was the highest ceiling in the building, located at the very back of the climbing area: this was a nine-metre span. It can be seen at left in the illustration above.
The mezzanine level, which was a substantial 12.5 meters above the reception area, was the other big span that the design team had to deal with. The following illustration highlights both locations.
The rationale behind Sylva CLT Rib’s
Sondre outlines the reasons why Sylva CLT Rib was perfect for these uses: “The main architectural feature in this building is the solid CLT frames used to enclose the space, with a frame geometry changing at each grid line to give the users the feeling of climbing inside a cave. The frames follow a certain grid spacing with a specific and unique geometry on each frame to create that feeling. We couldn’t – and didn’t want to – change this.” “The reason we have Sylva CLT Rib in the high roof, with respect to the other parts of the ceiling, is the distance between the last frame and the second-last frame. That span is larger compared to the other spans.“Then you have the mezzanine above the entrance area of the building. And again, here we have a large span. It’s 12.5 metres spanning from the outer wall to the central axis of the building.”
Why would you choose CLT panel?
The client chose mass timber, but alternatives briefly considered for climbing center parts. “In the initial phases, we were evaluating up to three alternatives,” continues Sondre. “But you wouldn’t have managed that with ‘pure CLT’, even if you wanted to. I don’t think we could produce such thick CLT to actually bridge that span. It would have been so inefficient in terms of material use that it wouldn’t make sense at all.”
“Another alternative was what we might call a ‘traditional’ CLT system, where you have load-bearing beams and you span CLT in the opposite direction between the beams. And on each side of the beams, you need either columns or a load-bearing wall. It was only one or two weeks into the discussions that we proposed Sylva CLT Rib as an alternative. Because it was very obvious for this project, to be honest. So we didn’t waste too much time before we actually took the decision.”
Why is the efficiency important?
Høyt Under Taket was the first time our Sylva CLT Rib was utilised by both the architect and the engineer, despite their extensive experience with CLT. Similar to Sondre, Bård was persuaded by the challenge’s efficiency. “We had a six-metre grid in the middle of the building but the idea was to make it wider at the end to have an extra climbing route,” says the architect. “Extending the span to nine metres increased the structural load and deflection demands, so we needed a more efficient solution. That’s where Sylva CLT Rib came in – it allowed us to span the distance without adding beams. “In a way, then, we had to work with a structural grid and also a climbing route grid. We placed our structure where it was structurally sound but also where it fitted according to the climbing width needed.” he concluded.
Conservation of area and Preservation of aesthetics
Sylva CLT Rib maximised vertical space efficiency and load-bearing capacity for the climbing centre by eliminating wasted space in the ceiling area and excluding the ‘beams alternative’. “At the back section of the building, you can see that the climbing walls go all the way up to the ribs,” says Sondre, with reference to the illustration below. “That was the consideration: if we introduced a very big beam to support the roof elements, we would enter the climbing and safety zones. You would lose the last metre and a half of climbing by having these big beams… instead of the many small ribs in Sylva CLT Rib.”
Despite climbers not being active below, conserving space in the shallow area was still crucial in the planning process. “The alternative there would have been to have beams between the walls, and then switch the span direction of the slab elements. But the height of these beams would have been maybe a metre instead of the half-metre ribs. You would steal so much room height in the reception area.”
The design team used the Sylva CLT Rib to improve ventilation efficiency by channeling air effectively through the rib structure, allowing for installation on one side without intruding on the exposed wood aesthetic. “That’s the best idea we had for using the structure with a purpose beyond just load bearing,” says Sondre. “I think it turned out well.”
When the workflow is seamless..
Despite being new to Sylva CLT Rib, the design team’s prior CLT experience made aspects like fire safety and connections straightforward. The Høyt Under Taket project benefitted from efficient prefabrication, with an easy process of optimising Sylva CLT Rib deployment. “Just by following the right steps, it was straightforward. There was a good amount of input data available. In the preliminary stages, we used product booklets and StoraEnso’s Calculatis software for evaluation. In the detailed design, a finite element model was used for analysis and verification of the timber structure.”
Norway’s Høyt Under Taket Climbing Center
Mastering the appearance and experience
Sylva CLT Rib aided Høyt Under Taket’s designers with structural stability, vertical space use, material efficiency, and wide spans, resulting in a design that pleased the lead architect. “When you come into Høyt Under Taket, you have a feeling that this is really spectacular. You have timber all around you,” expresses Bård. He continues, “It feels very light and spacious. Also the depth of the structure; you can feel there is space continuing behind it.
“The use of timber has a huge benefit for the indoor climate, especially with a sports centre like this. The whole building breathes because there’s no plastic in the walls.”
The climbing centre in Skien’s success led to a second centre commissioned in Moss, validating the design team’s work. “The idea was for this to be a modular framework that you could adapt to different sites,” states Bård. “We hope that Moss is one of the first offspring and then there can be more.
“I love the idea of using it more for these sports halls. It can create a lot of space as well as a room that breathes and feels more open, which is especially good for sports and leisure.”
Satisfaction driven by inspiration
The project, which demonstrated a range of other uses for Sylva CLT Rib, also inspired Sondre. “The main advantage of using those types of products is to create flexibility in the area underneath, so you avoid having support points like columns. So you can span longer… and the obvious type of buildings would be halls. It could be sports halls or factories or it could be large storage areas. Or it could be a theatre or something like that, where you don’t want the columns to disrupt the space. “But you can also add it into other types of buildings where you want flexibility in the future,” adds Sondre. “Sometimes you’re building an office area with certain internal walls, but then ten years later you don’t want it to be an office anymore, right? Now you need another layout, but maybe you’re bound because of these columns.
“However, if you have used another type of product, for example Sylva CLT Rib, you don’t have the column. So you can just freely move the internal walls almost any way you like.”
Sylva CLT Rib offers limitless possibilities under any ceiling, inspired by Norwegian freedom with the Høyt Under Taket brand originating from Høyt Og Lavt outdoor climbing properties. “You feel you’re more in a cave than in a hall,” concludes Bård. “It feels airy, it feels grand. It feels like ‘high under a roof’.”
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