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| ESB UBC - Great Fun: Great Contractor, Engineer and Architect. |
By John Boys
The new Wunderkind and current trend-darling in commercial
construction is cross laminated timber (CLT) panels. Paired with glue-lam
timbers and other engineered wood products it is making possible the construction
of tall wood buildings. CLT is being touted as the green alternative to
concrete, the building material that makes for speedy and efficient assembly,
allows for flexible and innovative design, and all at a competitive cost to
conventional materials such as tilt-up concrete.
And they are all of that – or rather they could be.
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| UBC O - Great Design/Build Team |
Our team has had more experience in the installation of CLT
in North America than most, and as
heavy timber specialists (with roots in
log-building and timber framing) we are excited by its potential and the
possibilities it affords, but concerned that if the bottom-line expectations
are not realized, that this revolutionary shift in how we build may disappear
before it has proved it’s potential.
On projects where we have been given sufficient time to
trouble-shoot, communicate, pre-plan and sequence our part of the work we can achieve the
“just-like-lego-time-lapse-look-at-em-go scenario” that we are all
anticipating. Our team thrives on the
well-coordinated dance of carefully rehearsed steps, meeting or exceeding our
planned schedule when we finally “go live”. Who doesn’t like to look good!
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| UBC-O; interesting design |
But it could be even better (and not only for us), if we and
some of the other key trades and/or material suppliers were allowed both information
and input much earlier in the design
stage. Pre-planning in isolation and extrapolating information from incomplete final
plans makes it awkward to contribute any solutions other than those which
address absolutely un-workable details and/or connections.
While most
trades people are not engineers, nor do all of us have a flair for design, cost
effective, safe and even elegant solutions at material interfaces can be
achieved if we are included (as appropriate) to define logical breaks in scope of work and to
consider possible challenges long before these issues come up at the
construction site.
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| UBC-O; connections +more connections | | |
And it is on
the job site, where the success of the design and planning can be gauged and
measured. Assuming that the prime contractor, heavy timber specialists and
material suppliers are competent, and that the plans and specifications are
well thought out, a wonderful and choreographed dance begins to take place. If
any of the above fall short, there are a lot of steel toed shoes getting
stepped on…
So how is any
of the above a “Problem with Cross-Laminated Timber”? In reviewing my words, it
reads more like a rant about not being included!
In part, it
is. I believe there are two things that threaten the future use of CLT in
commercial structures, the first that we are often treating a new
material as a substitute to the well understood materials (such as tilt-up
concrete) to which we are accustomed.
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| 3 D modelling. Not just for architects any more! (UBC-O) |
Do we anticipate the challenging characteristics of this
organic material (UV, rain, snow…shrinkage, expansion, iron staining…) and the associated
costs? And are we taking full advantage of the benefits (precision CNC
prefabrication, light weight, high strength to weight, visual qualities,
insulation...)?
What tolerances are achievable and how does that affect
specifications? Do the connection methods allow us to efficiently bridge the
differing tolerances? Concrete+/- 30mm, steel +/- 3 mm, wood +/- 3mm,
engineered connectors +/- 1mm, glazing systems....?
Using this new material effectively, in my opinion, requires
a mind-shift that addresses its individual properties as well as a re-think of how
we connect with the other components of the structure, and goes back to my
pre-amble on pre-planning and brings me to the second point:
Pre-planning resolves breaks in scope, discovers solutions,
arrives at efficient procedures and defines what is expected of the trades and
helps them to submit well considered and inclusive bids resulting in fewer
change orders and realistic budgeting.
In short, pre-planning can save money and my money is on the bottom line
when determining the future of CLT.
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| UBC O CLT: as Espressed Structure; the talents ofMcFarland-Marceau |
A great deal of our inspiration for CLT in North America is
derived from the success stories in Europe and the common factor in all of
these examples is that all the projects were built on a foundation that
incorporated sophisticated 3D modelling and that a great deal of time (and
money) was spent in pre-fabrication and sequencing strategies.
3D modelling and pre-planning means a significant up-front
investment.
It also involves a radical shift in how we approach design, engineering
and the bid process and it allows all of us to be accountable. I wonder if that
is possible…However it seems logical and expedient, that a revolutionary new
type of structure should also generate a radical change in how we work
together.
In closing, the “Log
Builder’s Wife” tells me she could have made the point a bit more succinctly;
her quote on the topic: “We can sing Green till we are Blue in the face, but if
Green equals Red, then Black will trump Green!”).
I could go on at length and in more detail on this topic,
but perhaps that is better saved for another day. In the meantime, I would be
interested to know if I am alone in my concerns for the future of CLT in North
America. Your comments welcomed.
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| "I'd like to harp on 3D modeling a little more..." |
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