Why this mountain bike center is built of Brettstapel, and why North American builders should be using this stuff
Coed-y-Brenin is a hugely popular mountain biking destination in Wales, ” the original mountain biking centre, where it all began. From retro, rocky, classics to modern contempory trails, there are rides to satisfy first timers to seasoned pros!”
Architype Architects have designed an extension to the original building that has a bike shop below and meeting rooms above. That’s a fun use and it is an interesting building, but the real buzz is about the Brettstapel.
Brettstapel is a method of making massive wood panels out of smaller pieces of wood, resulting in large panels that can be used as structural walls and slabs, much like Cross-Laminated-Timber (CLT). The use of CLT or other massive wood technologies can help substitute renewable wood for concrete, which has a very high carbon footprint, in many projects.
However, unlike CLT, Brettstapel doesn’t need million dollar presses and a lot of glue holding everything together. It’s much simpler; In this case, local Welsh wood (there is a lot of it) is sustainably harvested and milled into this shape which interlocks.
When Brettstapel (literal translation “stacked planks”) was invented in Germany in the 1970s by Professor Julius Natterer, it was simply nailed together. In the 90s it got more sophisticated; as James Henderson of the UK site Brettstapel explains,
Dübelholz, German for “dowelled wood” refers to the inclusion of wooden dowels which replaced the nails and glue of earlier systems. This innovation involved inserting hardwood dowels into pre-drilled holes perpendicular to the posts…. This system is designed to utilise a moisture content variation between the posts and dowels. Softwood posts (usually fir or spruce) are dried to a moisture content of 12-15%. Hardwood dowels (mostly beech) are dried to a moisture content of 8%. When the two elements are combined, the differing moisture content results in the dowels expanding to achieve moisture equilibrium which locks the posts together.
The 5-1/2″ layer of Brettstapel acts as the interior finish as well as the structural support. 3/4 plywood is nailed to the back of it to help stabilize it, then it is insulated with a foot of Warmcel (cellulose fiber) insulation. The exterior is clad in board and batten siding. It is all as environmentally sustainable as can be; the architects note that this is supposed to be a demonstrate:
- Innovative use of Welsh timber as far as practically possible and economically viable, to include structural and non structural elements, using techniques that could be repeated on future projects elsewhere.
- Healthy building with excellent day lighting and ventilation.
- Durability externally and internally; will need to withstand heavy use for many years to come.
- Special character of the location should be preserved and enhanced, and acknowledged in choice of materials.
The Brettstapel technology was chosen because the Forestry Commission “requested that the building should be a showcase for Welsh timber and timber products, using an innovative construction method and Wales’ huge stock of low grade, fast growing softwood, Larch and Sitka Spruce.”
Brettstapel had been done before in Britain but with imported panels. This was the first time it was actually made in the UK.
It wasn’t easy. Project architect George Mikurcik had his hands full; a case study of the project noted that trades were hard to convince, moisture content was difficult to manage (because there was not really all that much knowledge), the weather was terrible, normal construction arrangements didn’t work, “From start to completion the project took five years, demonstrating the difficulty in driving innovation through the bureaucratic process. It was however ultimately well worth the effort with technical solutions now available for wider application within the industry..”
But they ended up with a lovely building, inside and out. Here is a timelapse of construction:
So why is this so important?
Across North America, the mountain pine beetle is devastating forests. If it just rots, the CO2 it is sequestering is released back into the atmosphere. The hugely valuable asset is lost. To promote use of more wood, building codes are being revised to allow for taller buildings made out of massive wood like Cross Laminated Timber.
But it takes time and a couple of million dollars to set up a CLT plant. The Coed-y-Brenin Visitor Centre demonstrates that with a bit of a push, local mills and local trades can build a massive panel using simple technology and get much the same result as with CLT: a solid structural panel that is strong, earthquake and fire resistant, and good looking.
The technology demonstrated in this little building in Wales should be emulated and adapted in North America. Today.
Nice work by George Mikurcik and Architype; more information here.
More on Brettstapel in TreeHuuger: Brettstapel: another way of building with wood