A Nordic Gridshell first

Kuokkala church exterior....photo Jussi Tianen

Of all the 'newly drawn' generation, Lassila-Hirvilammi are the only architects who have built their reputation away from cosmopolitan Helsinki. Their path has been different in other ways as well, including the first attempt at a full-scale gridshell - Kuokkala church in Jyväskylä - across the whole of the Nordic world

"There was nothing ironic about it" states Teemu Hirvilammi down the line from mid-town Seinäjoki, in mid-west Finland, when I ask him about the possible ironies of one of the oldest timber cultures playing catch-up with the wave of early 2000’s rush of gridshell structures which emerged in Britain and elsewhere, during the first half-decade of the new century. Hirvilammi, is the junior of the two practice partners, having begun studying at Oulu Architecture school two years after practice founder, Anssi Lassila. Lassila-Hirvilammi are one of the group of younger Finnish architectural practices who have received international attention in recent years, though as insider-outsiders, due to being the only non-Helsinki based practice of this Newly Drawn generation. The project we’re discussing is their 2010 Kuokkala church, with its striking interior diamond lattice gridshell-like weave echoing the rise and dip of the buildings roofline.

...and interior. Photo Mika Huisman
"It was just a motivation. If others can do it, why can’t we?" he adds, after I had asked where they had looked for inspiration for their gridshell structure, Teemu pointing out how Southern England’s Downland gridshell had opened their eyes to what was practically possible. And, after a fashion, they have, making Kuokkala Finland’s first stab at a full-scale gridshell building. The Finns have paradoxical form when it comes to catching up, rather than leading Europe in timber building advances. In the late nineteen nineties as the first surge of renewed interest in new timber buildings in the country began to consolidate, the story goes that research visits were made to central Europe to re-learn aspects of carpentry and structural techniques which were once part of Finnish building expertise but had almost completely disappeared from theirs, the most heavily wood covered country in Europe. Now, a decade and a few years on, the Haltia Nature Visitor Centre (as featured in this Finnish focused Unstructured Extra,) is the first Finnish Cross-Laminated Timber (CLT) project to be completed, eighteen years after the first German CLT project. In the next couple of years the Finnish construction sector will dip their toes that much more deeply into similar water, with a first CLT high-rise in the capital So, in a way, the Kuokkala gridshell project got in comparatively early.

Carving the build
The church completed an early trilogy (trinity?) of religious church buildings, which the practice have built much of their youthful reputation on. It is also a return to the use of timber. Lassila’s student project Kärsämäki was a different kind of timber building, though, as it was to be designed, built and completed only using old non-mechanical tools and without electricity. And not surprisingly both are adamant that they are not wood architects, and use a full palate of materials, stone, copper, and concrete, with their second Klaukkala church was in concrete with a copper façade. They are also clear that they are not to be pigeon-holed as church architects, even if their fourth church is presently underway.  as their industrial Frami D2 building, and now their first cultural commission, the Tornedalen Culture House each illustrate. Yet Kuokkala is an essay in timber architecture, for which Lassila and Hirvilammi have created a large barn-like structure resting on a sloping site, which required a split-level building at the end of a public precinct in Jyväskylä ‘s Kuokkala suburb. In the period since it’s opening the church has received attention across the international architectural media, in significant measure because of its lovely interior grid of locally sourced latticed spruce. Completed, the result remains uplifting as one enters the churches interior, the thin interlacing lathes softening and organicising the already fully wooden surfaces. Visiting on a Sunday morning last summer (2012) while attending the Aalto Foundation’s Crafted conference, the lightness within the main church was apparent, complementing the ceilings wave-like curving slope, continuing gently until reaching the lower vertical walls. Decked out in the softening colour of white spruce, this lightness is in pronounced and vivid contrast to the external dark slate facade, while the divide between the lower front of the building, and the raised rear level, suggests an absence of complete resolution is at odds with an expectancy of harmony in a sacral building.

Inside in... the latticed shell, and spiral staircase

The lath lattice is sadly a sleight of hand though. The gridshell wasn’t completed as originally hoped, as the wider engineering and building team contracted turned out not to have sufficient expertise and experience to realise a ‘genuine’ gridshell design. So, what one experiences looking up at the church’s woven grid is decorative rather than structurally necessary. Which is also why it is the second of two structural skins, the combined roof and wall comprised of a glulam frame adjoined to the gridshell, with both built on site to stand over the three separate parts of the building.

Ville Hara's Kupla 'bubble'
Jussi Tiainen
and the Downland gridshell
Katherine Rose
Things didn’t start out this way, however. Actually, Finland also already had form in gridshell structures. In 2001 Ville Hara, then a young student on Helsinki Technical University’s Wood Studio course proposed a woven gridshell structure, which went on to be the course project for the year. Kupla, which is discussed elsewhere became a leit-motif for the young generation Hara, Lassila and Hirvilammi are all part of, a suggestive hint of a new openness and that further Finnish timber experiments were to follow, including gridshells. But then they didn’t. That is, until Kuokkala. Perhaps surprisingly, Hirvilammi states that although they were aware of Hara’s Kupla project it didn’t have that much influence on him or Lassila. First becoming aware of the lightweight structural approach through magazine articles about the Japanese pavilion by Shigeru Ban and Frei Otto for the 2000 Hannover Expo, this didn’t apparently extend to Otto’s pioneering work with the Stuttgart Institute of Lightweight Structures. It was only when they encountered the considerable publicity surrounding Cullinan Studios Weald & Downland Museum gridshell in the slipstream of its 2002 opening that they began to pick up on the possibilities and turn them over in their minds up in the middle of Finland. “We studied it and were fascinated,” says Teemu. “There was a lot of documentation available. Anssi first saw the project at a wood seminar he was attending. It was the first time I thought that a gridshell could be made at such a scale, for an actual building.”

There was no particular idea of wanting to ‘do a gridshell’, he says, waiting until the right project came along. Rather, the idea, when it came, originated quickly, as they began working over the summer 2006 with their junior architectural partners, Oulu’s Luonti Architects, on the new church competition. The Downland Gridshell studies had been absorbed and the idea of a structural gridshell structure “captured our attention just before the competition. There was the possibility of a rich structural interior, and also it felt like the right context.” There were other pragmatic reasons. As a structural canopy, the lightweight shell worked well to unify the disparate floor plan, divided into three parts while also visually compelling. Last, but not least, a gridshell felt like an apt structure for a church, which the pair already had a background in.

Lassila and Hervilammi were also confident that they could find engineers, carpenters and other specialists for the project. They believed that their project would catch the attention of the competition organisation and the jury, not least that its novel structural element would appeal to the jury’s architect, Aalto Uni professor, Antti-Matti Siikala. Winning the competition felt like vindication of their decision to integrate the gridshell. “They believed in us, in what we could build. They never thought we weren’t able to build it, but did ask how we would do it. Of course we realised that a gridshell had never been built before at such a building scale, but we thought it would be possible, and demanding, and we tried to play an active role in choosing the contractors.”

The choices, however, would be made separately, some months after the architectural competition, and although Lassila-Hirvilammi proposed a number of engineers “with quite excellent reputations” the organisers made their own decision, and although involved, the architects role turned out to be smaller. The church client decided on appointing the local Jyvaskyla office of the Danish engineering giant, Ramboll Finland, alongside Late-Rakenteet, a Turku based carpentry company who had considerable experience with larger timber projects, including an ambitious sports arena, in the city of Joensuu to the far east of the country.

Modelling the inside and out
The first stages of the building design, optimising space and other aspects of space planning, began smoothly enough. They also initiated investigating the design with models, which had always been a part of their practices approach. The first model was small, at 1: 200 in order to begin studying the form and shape. Lassila, used tools and small-scale machinery in his home workshop to experiment with the shape, carving out forms with blocks of wood.  In the main studio further larger models were completed. “At the time we were really lucky to have a highly, highly skilled model maker, the best I’ve ever met in our practice so far, working for us.” A 1:100 scale mock up was built to study the design’s 3D qualities, and their relation to inner and outer, with removable cladding to be able to look inside. “It was actually quite a complicated construction to work with the form and with the exterior” say Hirvilammi today. “We also realised we were not skilled enough at the time to understand the geometries involved. As the project progressed, computational modelling became more central and, since the project computers have made that aspect much more accessible and faster and interesting. Algorithmic programmes would have been helpful, although I think the end result would not have been the same” As it was, as autumn 2006 gave way to winter 2007, the office didn’t initially have the right computer programmes at their fingertips. “We needed really good models.” One of the last of these models scaled the project up, a 1: 20 model of the main hall itself.

1:1 - Working on the shell-roof structure at full scale
Meanwhile the engineering was beginning to unravel. Ramboll had been appointed before any of real design work on the shell structure had begun and with Lassila and Hirvilammi looking in from the outside unable to influence the decision, the engineers had been contracted onto the project without prior knowledge that they were to be working on a gridshell. Hirvilammi stresses that the gridshell was only a part of the problem and that the financial side; keeping on top of tight budgets, and also regulatory requirements for highest ‘AA grade’ engineers to be on board, were also significant. Still, within the first six months of 2007, it was becoming clear that the Ramboll office wouldn’t be able to engineer a load-bearing gridshell. A mixture of no-one knowing how and the expense of the learning curve to be able to do so, brought things to a halt.

A rethink began. Lassila and Hirvilammi arrived at a compromise design decision. There would be two structures, a primary load bearing structure comprising a 13 glulam timber frame truss to hold up the roof and building, and a secondary gridshell lattice, which, no longer structurally necessary, would remain for primarily aesthetic and decorative purposes. Today Hirvilammi acknowledges that they weren’t at all sure about continuing with a notional gridshell, in order to make the building look good. It seemed to defeat the object. “When it is only a secondary structure what is the point of it?” he states rhetorically, recalling how they spent many days drinking coffee arguing the merits of keeping or not keeping the lattice. “We were very critical. But in the end we decided it was just visually so strong, that we agreed it should be there.”

Ramboll's BIM modelling
Other problems were conspiring and complicating the design. The engineers, now working with this new double structure, were coming up with ever more complicated designs, which were beginning to get out of hand.  “The real difficulty was in making the jointing system work.” The engineer’s solution involved a larger canopy and individual joints across the whole shell. “It wasn’t the engineers fault, they just had to do the project, but Anssi was getting a bit frustrated and went to see Rudi Mertz, an old carpenter friend within the Southern Finnish Fiskars craft and design community, who we’ve worked with all through our projects. He was really helpful, making one joint for each connector work throughout the whole lattice.” The design was able to proceed again, aided by the introduction of Rhinoceros software for modelling the church, with further work being done by Ramboll Finland using Tekla, Bim-modelling. A combined glulam frame truss and gridshell design began emerging; with individual, customised glulam frame sizes, becoming lower and narrower along the churches hall. This double structural result, glulam frame married to gridshell couldn’t be described as a conventional wall and roof, even if its steeply sloped faces touch down onto concrete walls, joined in place by steel pins, on each side of the building. The design was intricate and complicated, involving considerable time put in on structural geometry. Construction begun in 2008 and a year later the engineering would win Ramboll Finland 2009’s Tekla Structures computer modelling award, a point Hirvalammi underlines, keen to praise Ramboll’s contribution to the design.

eaves-dropping - shell and glulam frame joined
Mika Huisman
There were also problems with the building costs gradually creeping over budget, and the pair worked on the re-design to simplify other aspects and value engineer other parts, including lowering the roof. By the end of the process they estimated they’d put over 8000 hours into the Kuokkala. They continued, however, to doggedly hold on to, “our dream of keeping the gridshell. It was difficult at the time but today I can easily say it was the right decision.”

Reflecting back on the visit to the church the august sunday last year was a reminder of the trials that had gone on to get the project as far as it did. The lattice canopy brings another, almost intangible, quality to the interior, even though I knew, and noticed how the canopy was fixed to the primary glulam wall. The ashwood pews and other church furnishings, along with the altar made from limewood, and the altar wall artwork by Pasi Karjula combined to complement the atmosphere created by the light spruce. How different might it have been if Lassila and Hirvilammi had been able to complete their original plan, a genuine single structural gridshell holding the whole building in place? If the separation with the exterior – a point of focus of some critiques, noting how the dark grey slate exterior feels almost like another separate building – has moved the upper interior surfaces a further separating step away, the gridshell-like interior continues in its capacity to bring those who come upon it to pause for a moment and draw breath at the overall experience. The completion of Kuokkala church also means there is ‘almost a gridshell’ now in Finland. Hirvilammi, when asked, says they don’t have any plans for another attempt to nail a real, rather than authentic reproduction, gridshell at present. He does think how much easier their work would be to do, with the computational form-finding tools available today, the significant knowledge learnt during the years Kuokkala was in design, and the overall increased timber knowledge and expertise in the construction sector. “if the circumstances were right” he says. Meanwhile Finland’s remaining 3000 or so architects have two gridshell type exemplars in their midst, which is twice as many as almost every other European country. It seems almost impossible to imagine that in a country with such a forest culture heritage, one of those 3000 won’t contemplate another bite at the cherry. Of course, they may already be doing so right now.

Seasons they change - tho' inside stays the same