kreuzlagenholz | cross laminated timber

  

For years as a student, I dissected wooden construction details in Detail, wondering why they appeared so foreign to my American eyes. After a long and difficult search, the answer became apparent: Cross Laminated Timber (CLT). As a young architecture praktikant in Germany, I quickly realized everything I knew about wooden construction was outdated, inefficient and irrelevant. My first experience with modern European timber practices was a polycarbonate-wrapped house that utilized brettstapel (mfr: Bresta).  

 Brettstapel is, effectively, 2x boards mounted on dowels that are fabricated off-site and erected as panels. Quick, easy, effing brilliant. Brettstapel can be utilized for walls, floors and roofs. The products are available in various dimensions for acoustic and visual preferences.

From here, my spidey-intern senses went nuts, and I realized that there was something very desirable, very sexy about these panels. It comes pre-finished, installs quickly, incorporates low-grade rapid-growth lumber effectively, sequesters carbon and can be optimized for thermal storage (a topic for the next post).  Amazingly, building with  CLT is like building study models with chipboard – you place a window wherever you want.  

 Cross Laminated Timber is made by laminating dimensional lumber at right angles, similar to plywood – on steroids. The result is a prefinished material (optional) that is dimensionally stable, capable of spanning large distances, reduces construction waste, increases airtightness and can be rapidly erected. The cross lamination decreases swelling/movement and thicker panels don’t require a vapor barrier. The prefabricated panels can be brought into challenging sites, as in Hermann Kaufmann’s  Olpererhütte in the Austrian Alps – helicopters lifted the panels to the construction site 2,400m above sea level.   

CLT technology has been perfected in the Bregenzerwald (surprised?) and is utilized on projects all over the world, including the Österreich-Haus for Team Austria in Whistler.  

Recently, a 9-story building by Waugh Thistleton was completed in London. Except for the foundation and ground floor, the entire building – including elevator and stair cores – is composed of CLT panels. Woodworks has an excellent pdf on the 9 week erection process. This is ‘platform framing’ for modern engineers. And speaking of engineers, CLT could prove to be extremely beneficial in seismic areas, as seen by this simulated quake on a 7 story CLT mock-up.  

Hopefully, the Austria House in B.C. will have a positive regional impact. I contacted Weyerhauser several years ago about CLT, they said they weren’t interested and there wasn’t a U.S. market for it. Apparently Weyerhauser didn’t want to expand their client base and have opted to let the Austrians invade. Earth to struggling lumber plants: the Canadian Wood Council is on board. Perhaps the process of testing and approval for the U.S. market may be a hinderance at present, but who doesn’t to build with these?!?

  • http://blog.buildllc.com/ Andrew

    This is great information and exactly the type of discussion we need in the U.S. to raise the bar of design and construction to a more sophisticated level.

  • http://www.postgreenhomes.com chad

    Awesome. Thanks for finding and sharing with us uneducated Americans.

  • Richard

    Nice work. I am writing a similar article and I am amazed at the lathargy with which CLT is spreading globally. N. America, especially, is already used to prefab and this looks so much nicer, locks up a lot more carbon whilst insulating itself and without a complex medley of materials and chemicals.

    I hope all architects (I’m a forester) have access to this material withing this decade, if not next Wednesday.

    • http://www.smartwoods.com patrick

      we are launching the first of its kind CLT manufacturing plant in Northwest Montana for all of the reasons stated above and more. hope to be operational by next spring and in the mean time we are importing demonstration projects from europe. the time is now!!!!

  • http://bruteforcecollaborative.wordpress.com meliason

    patrick,
    we ran across your site/blog a few months ago, but didn’t realize you’d be manufacturing CLT in the u.s. – this is great news!

  • http://www.smartwoods.com Pete Kobelt

    Look for the first CLT demonstration project coming soon. In addition to Whitefish, MT we will be announcing the locations of other projects soon. We are actively seeking a prefab partner that would be interested in utilizing CLT in a prefab. It’s a natural fit.

  • http://www.gaiagroup.org sam foster

    Hi,

    Information on brettstapel is now available at http://www.brettstapel.org

    As far as I know it’s the only comprehensive set of info on this system in English.

  • http://www.gaiagroup.org sam foster

    Hi again everyone,

    Sorry, meant to say in the last post: there’s a clear distinction between cross laminated timber (CLT) and Brettstapel.

    Both are termed ‘massive timber’ or ‘massive wood’, for fairly obvious reasons. Under this umbrella heading we tend to refer to panels which use glue in their constructions as ‘cross laminated’; any form of panel which uses timber fixed with dowels, nails or screws we refer to as ‘Brettstapel’ (literally ‘stacked boards’).

    The Österreich-Haus for Team Austria in Whistler is made from the latter – unglued timber held together with wooden dowels. We have worked with the same company on a new primary school as well as a new private house, both in Scotland.

    We have opted for the unglued system rather than the cross laminated as we have concerns about the impact of glues on indoor air quality, though not everyone shares our concerns!

    I’m happy to share info if anyone’s at all interested.

  • http://www.oregoncanadian.com/products.htm Softwood Timber merchants

    After the recent blaze in Peckham, London, what do CLT building stand to lose from a change in fire safety regulations?

  • http://www.gaiagroup.org sam foster

    Hi Softwood Timber merchants,

    Unfortunately both the big insurers (Zurich & NHBC) and now the fire brigade are bringing their long-held concerns over timber construction into the open and the media is dutifully spreading the message.

    However, they both represent different interests: the insurers are concerned about property, while the fire brigade is concerned about people.

    As far as people go, buildings are not usually occupied until they are complete, by which time they should be perfectly safe, whether built of timber or not.

    Massive timber, by its very nature, can withstand extreme fire loads and maintain structural integrity better than steel or concrete buildings, which I’m sure you know this already. Numerous tests have demonstrated this. However, without some form of suppression, eg sprinkler systems or fire-retardant coatings, the big problem with any timber structure, massive or framed, is surface spread of flame.

    During construction of a massive timber project (be it CLT or Brettstapel) it’s unlikely that there would ever be any form of suppression installed to deal with a fire, so if one breaks out then it’s likely to all go on fire, though not necessarily collapse.

    Perhaps the UK should introduce more rigorous requirements for cavity barriers, or physical fire breaks in construction, eg between floors, or demand that combustible elements are temporarily protected during construction.

    But, to answer your question (!), I’ve not a catch-all solution; whatever happens should be addressed by everyone who will be affected (including companies like yours), otherwise the timber construction industry is set to lose out.

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  • Mario

    I think that “X-LAM” (X=cross-LAMinated) is a more international friendly denomination than “CLT”.

    Cheers.

  • Bealla Baldwin

    Hi, How well does this building system perform in countries with a heavy rainfall, and where blown rain is a problem on sites near the sea?

    How does one stop the egress of water, and have there been problems with delamination.

    Are hearvier fittings needed in earthquake prone regions

    I would be grateful if someone out there has the answers to this problem.

    Denise.

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  • Sam Foster

    Hi,

    Really great to come back to your blog after a few months away, and fantastic to see so much progress on Brettstapel and CLT over in the States.

    Couple of quick things: re your concerns over achieving a decent blower door test (in one of your other posts), a Brettstapel house (by Gaia Architects – http://www.gaiagroup.org) recently achieved 0.46ac/h @ 50Pa on the pre-handover test. One of my friends achieved 0.3 on a timber frame house…as ever, attention to detail and an understanding contractor are key requirements.

    The other thing is just an update on where things are at re CLT and Brettstapel in the UK…Napier University have recently purchased a CLT press to make and test panels from Scottish timber, Forestry Commission Wales are experimenting with homegrown Brettstapel and there are lots of studies being done on performance.

    How are you guys all getting on making X-Lam (sorry Mario!) and using it?

    Sam

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  • jonathan

    What do brettstapel and x-lam panels cost vs. regular stud framing?

    The idea is interesting, it seems a more polished form of log home construction (same concept: massive timber wherein the natural cellular form meets both load bearing and insulation requirements), what is the impact on construction budget?

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