Timber is one of the most versatile building materials on the planet. But too often the material is misused or incorrectly installed, compromising its
properties.
Timber is one of the most versatile building materials on the planet. But too often the material is misused or incorrectly installed, compromising its
properties.
How to choose the right timber
Good wood, bad wood
some hardy hints for specifiers
Timber is one of the
most versatile
building materials on
the planet. But too
often the material is
misused or incorrectly
installed,
compromising its
properties. Stephanie
McDonald reports.
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AFS-certified flooring
Hardwood framing
Boral Timber
decking useed as fencing
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Boral Timber parquetry
Boral Silkwood in Brushbox -
wide boards
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Decking maintenance
One of the most important
aspects of using timber is
selecting the right species
for the right application.
Stephen Mitchell, sustainability
programme manager at the NSW
Timber Development Association, says
other key characteristics which affect
choice are strength, appearance,
durability, moisture content - which
affects shrinkage rates - density,
hardness and fire indices.
He says some common mistakes are
made by confusing the properties of
timber, such as confusing structural
grades with natural durability classes;
confusing natural durability and
preservative hazard classes; and
specifying seasoned (kiln-dried)
hardwood timber in sizes above 45mm
thicknesses, which are hard to source
or have long lead times.
"It is common for designers to have a
good idea of what they want something
to look like yet specify the wrong
timber or detail to fit their idea. This is
particularly the case in exposed
external applications where natural
durability, preservative treatment and
finishes are all important
considerations," Mitchell says.
Tim Sherry, marketing manager at
Carter Holt Harvey, agrees, and says it
is common for the wrong product to be
used versus the architect's vision.
"Timber selection is often driven by
availability and pricing," he says.
Robyn Barnes, marketing manager
at Boral Timber, says mistakes can
also be made due to a lack of
knowledge about timber. For
example, not understanding the
natural features and variations of
timber. Also, over specifying the
material can be a problem.
"Building designers are often driven
by their goal of a particular aesthetic
outcome, which means other attributes
********* TEXT BREAK ********* of a species selection, such as hardness
ratings and certification, can be
overlooked," Barnes says.
"We also find that because of the
shared responsibility in building
projects, the lack of detail when
specifying can lead to ambiguity and
the substitution of the wrong
product, which may not meet the
desired outcome."
Mistakes can also be made when it
comes to installing timber, such as not
installing enough structural bracing,
particularly during construction,
according to Mitchell.
Also, timber flooring installation
needs adequate gaps around the wall
so the timber can naturally expand and
contract, which can be easily forgotten,
according to Mitchell. He says
inadequate drying out or drainage of
the sub-floor area and not taking into
account air-conditioning and heating
cycles when the building is complete
can also be problematic.
Choosing the right timber species
often comes down to a number of
********* TEXT BREAK ********* factors. According to Barnes, things to
consider when it comes to flooring are
the colour and aesthetics, traffic flow
and what type of project it will be
used in. When it comes to structural
use, codes and regulations often take
on more importance, such as BCA
and Australian Standards
requirements for strength, durability
and bush fire ratings.
Barnes says there are five key steps
designers can take to ensure the
successful use of timber. These
include:
1. Establishing the usage application
and working backwards.
2. Selecting a species. As well as the
aesthetic, other factors such as the
aspect or traffic that the timber will
be exposed to will to determine the
most suitable species and finishing.
3. Informing the client. Relationships
can be tested when the picture in a
client's head does not match the
end result. Explaining the natural
colour and feature variations that
occur within timber products can
help prepare clients for the final
outcome.
4. Being aware of the variety of
product options. Finding the right
solution for a particular design is
broader than purely species
selection. For example, the type of
subfloor that a timber floor will be
laid over will have an affect on the
type of timber flooring product that
can be used.
5. Considering sustainability.
With over 40 major timber species
across six to seven major products
groups, it can be easy to see why the
material can be so easily misused.
Mitchell advises specifying timber
according to the relevant Australian
Standard. For example, AS 2796.1-
1999 defines the various properties for
the specification of sawn and milled
hardwood for flooring and cladding.
"For structural applications, the
best and most common timber
species are the softwoods radiata pine
and Douglas fir (or Oregon). We are
also seeing increased volumes of
some great imported softwoods, such
as various spruces and Baltic pines
from Europe and North America due
to the high Australian dollar,"
Mitchell says.
"The use of engineered timber
products such as I-beams,
laminated veneer lumber (LVL),
plywood box beams and glulam is
also really taking off.
"The most common mistake made
with structural timber is not realising
the increased span these new
engineered timbers can give.
Specifiers also need to be conscious
of the correct hazard level for a given
application."
Specifiers have ample resources
available to guide them. For example,
the Timber Development Association
in NSW and the ACT have on-site
technical CPD presentations on
specification, designing for durability
and finishes and coatings.
Carter Holt Harvey has a software
program called designIT for the
design of engineered woodproducts to
aid with the selection of beam sizes.
"The early specification stage is
suited for the supplier to work with
the architect as their idea is formed
when they know what they want to
achieve. Discuss the product's fit to
your vision," Sherry says.
Boral Timber also has dedicated
specification managers who can
advise architects and building
designers on their options for
structural and aesthetic timber use.
"The opportunity to use timber in
creative ways far exceeds its
limitations. We have seen our
structural F27 grade hardwood used
to design a bespoke benchtop in a
commercial setting and our standard
decking product used to make
decorative screens in an outdoor
residential space," Barnes says.
"Once you explore the breadth of
Australian hardwood species
available, you will be surprised at the
flexibility timber can afford a
building design.
"Once the initial concept is
formulated, a specification
professional within the supply source
can save architects and designers a lot
of research time by directing them to
the most suitable product options."
