RC113 JulyAugust 2024 - Magazine - Page 15
GAINING PERSPECTIVE
What changes when you are building with wood instead of concrete and steel?
by Vincent Davenport and Mark Gaglione
N THE EVER-EVOLVING LANDSCAPE of construction, a silent revolution is underway, and it goes by the name of mass
timber. While wood has proven its worth as a building
material over the centuries, mass timber is propelling it
into a new era de昀椀ned by sustainability, e昀케ciency, and
aesthetic appeal. As its popularity continues to soar,
it becomes increasingly crucial to grasp the distinctions
between building with mass timber versus traditional methods like concrete and steel. Additionally, uncovering the
parallels existing within these materials can o昀昀er valuable
insights, informing the construction process, and paving the
way for successful mass timber projects.
I
GOVERNMENT OF B.C.
Mass timber as a material and its procurement
While mass timber is fundamentally wood based, it’s
essential to distinguish it from the light wood frame structures commonly seen in residential buildings. While light
wood frame construction prevails, particularly in lowrise residential projects across Canada, the application of
mass timber transcends these conventional methods. Mass
timber projects stand out for their use of larger engineered
wood products, adhering to rigorous engineering standards. Originating from sophisticated supply networks,
these projects undergo meticulous engineering processes
distinct from those governing light wood frame construction. Within the domain of mass timber, four primary
types reign supreme: Cross Laminated Timber (CLT), Glue
Laminated Timber (GLULAM), Nail Laminated Timber
(NLT), and Dowel Laminated Timber (DLT).
Procuring mass timber products entails navigating a
complex network of manufacturers and integrators. While
some subcontractors specialize in producing mass timber
products independently, others serve as integrators, sourcing components from various suppliers and overseeing
the assembly process. Distinguishing between manufacturers and integrators is pivotal in formulating an e昀昀ective
procurement strategy tailored to the unique demands of
a mass timber project. By delving into the intricacies of
the supplier network and conducting a comprehensive
assessment of factors such as equipment capabilities and
expertise, contractors optimize their procurement processes, thus ensuring the success of their projects.
Building with mass timber
Mass timber boasts a distinct scheduling advantage,
thanks to its prefabricated nature, which expedites on-site
assembly. With pre-constructed beams and slabs ready for
installation, mass timber follows a similar prefabrication
process to structural steel and precast concrete, where o昀昀site manufacturing and subsequent crane-assisted installation are standard practices. When comparing scheduling
and installation analysis, mass timber aligns closely with
precast concrete and structural steel, with crane e昀케ciency
being the primary determinant.
RENEWCANADA.NET
Similar to precast and steel structures, mass timber
installations may not be entirely 昀椀nished upon installation.
There are often connections to be made or minor details
to address once the main erection crew has departed. For
instance, a concrete topping is frequently poured over the
mass timber structure on each 昀氀oor, mirroring practices seen
in precast and steel construction.
Despite the perceived schedule bene昀椀ts of mass timber, the
reality may vary depending on the comparison made. Notably,
signi昀椀cant schedule di昀昀erences emerge when comparing mass
timber to cast-in-place concrete. However, this comparison
is akin to that between cast-in-place concrete and precast
concrete or structural steel, highlighting the distinction
between on-site construction and o昀昀-site prefabrication.
Another parallel can be drawn when we examine the integration of mechanical and electrical systems. Due to mass timber’s prefabricated nature, like precast concrete and structural
steel, upfront coordination is essential for penetrations and
openings to accommodate necessary piping and wiring.
A notable divergence in the building process compared
to concrete or steel arises in moisture management. Wood’s
vulnerability to moisture necessitates meticulous planning
and proactive measures during construction. EllisDon has
undertaken comprehensive studies to comprehend how mass
timber behaves under diverse environmental conditions
including dry, wet and very wet climates. This knowledge
informs strategies we currently use on our projects across
Canada, such as employing resistant membranes or adopting
speci昀椀c labour practices to address issues like puddling. These
proactive steps mitigate moisture-related risks and safeguard
the durability of mass timber structures.
Mass timber design and aesthetics
Before commencing a project, we conduct feasibility studies
to assess the cost implications of constructing a mass timber
building. Clients frequently approach us with existing concrete
or steel structure plans, seeking insights using timber instead.
Mass timber’s distinct material properties necessitate a re-evaluation of optimal grid layouts compared to conventional concrete structures. What may be an ideal grid for concrete might
not be the most e昀케cient for mass timber construction. Factors
such as beam span and depth signi昀椀cantly in昀氀uence design
considerations, particularly regarding headroom requirements. For example, a beam comprised of mass timber can be
two to three times as deep than a concrete beam that spans
the same length. Adjustments to grid layouts are essential to
optimize cost e昀케ciency and structural integrity when working
with mass timber.
Vincent Davenport
and Mark Gaglione are
Directors of Building &
Material Sciences
with EllisDon.
JULY/AUGUST 2024 – RENEW CANADA 15
