SmartLam GL17C Brochure - Tilling Timber

PAINTING LOSP TREATED SmartLam BEAMS
Wait until excess solvents have evaporated and timber is dry.
The pressure of the solvent (white spirits) from the LOSP treatment
may affect the drying and hardening of paints if there has
been insufficient evaporation time after the treatment. It is
strongly recommended that the treated timber is left to recondition
for at least 7 days in the end use situation before painting.
Resin bleeding can occasionally be a problem with LOSP treated
softwoods. See “RESIN BLEEDS” below
One coat of premium quality primer as a minimum should be
applied to all surfaces prior to erection of beam and to any cuts
or holes drilled. If the first coat of primer, sealant paint or stain
fails to dry or adhere within the time expected, do not proceed
to any further coats until the first coat has achieved satisfactory
dryness and adhesion. If the first coat fails to dry it may be
necessary to strip back to bare timber and allow it to weather
for another week or two.
1 Paint
• Exterior solid colour acrylic finish. One coat of oil based
primer followed by one or two coats of the exterior
acrylic finish as required.
• Exterior solid colour oil based enamel. One coat of oil
based primer followed by one coat of oil based undercoat
(if required) then two coats of the oil based enamel.
2 Stains
Exterior semi-transparent or solid colour penetrating oil based
stain or similar. Two or three coats of the stain as required or
recommended by the manufacturer.
Water based stains and un-pigmented sealants, oil or water
repellents are NOT recommended.
RESIN BLEED
Resin Bleed may be identified by a sticky, clear or white exudation
that has a characteristic aromatic odour. It is most commonly
encountered around knots or other imperfections in the
wood and in places where the tree sustained damage. Paint or
stain will generally be softened and may even be lifted off by a
resin bleed.
If resin bleed occurs the following steps are recommended:
i. Physically remove the exuded resin from the
surface
ii. Allow to weather for a few days to ensure the
bleed has ceased.
iii. Seal the affected area with a suitable sealant
such as Resene Everseal.
Further advice mat be obtained from AS 2311
FIRE RATINGS (RESISTANCE)
In a fire, SmartLam GL17 beams have an inherent fire rating.
As timber burns, a layer of charcoal forms enclosing a core of
timber which is yet unaffected by the fire. This timber core
maintains its structural capacity. Hence, dependant upon the
loss of material to the charcoal layer, the SmartLam GL17
beam can carry the dead load of the structure for a period of
time.
Resistance to fire can be established by reference to AS
1720.4 Fire Resistance of Structural Timber Members, using a
charring rate of 0.66 mm per minute. Therefore, the strength
and stiffness after fire may be assessed using the uncharred
residual cross section computed for the period of exposure to
the fire.
CHECKING IN SmartLam GLULAM
One of the advantages of glued laminated timber construction
is that while seasoning checks may occur for the same reasons
that they do in sawn members, checking in glued laminated
timber will generally occur to a much lesser degree because
of careful control of the moisture content of timber used
for laminating. Checks in wood are separations along the fibres
normally occurring across the rings of annual growth resulting
from stresses developed during changes in moisture content.
Checks in glued laminate timber may appear as openings parallel
to the grain on the sides of members.
As wood loses moisture to the surrounding atmosphere, the
outer fibres of the member lose moisture at a more rapid rate
than do the inner fibres. As outer fibres try to shrink, they are
restrained by the inner portion of the member that has higher
moisture content. The more rapid the rate of drying, the greater
will be the differential in shrinkage between the outer and
inner fibres resulting in higher shrinkage stresses.
These resultant stresses perpendicular to the grain of the
wood can cause characteristic wood seasoning checks. The
influence of checks on the structural performance of glued
laminated timber members is generally minor. Checking can be
minimized by careful installation practices that avoid prolonged
exposure of the members during construction.
IDENTIFICATION OF CHECKING
Checks occur as transverse separations or openings that are
nearly parallel to the grain direction in glued laminated timber
and generally follow the grain direction around knots and along
sloping grain. Differences in the shrinkage rate of individual
laminations used is glued laminated timber tend to concentrate
shrinkage stresses at or near glue lines, resulting in checks.
Checks are often confused with delamination that occurs when
the glue bond is not adequate. The presence of wood fibre
separation in these openings is the key distinguishing characteristic
of seasoning checks. Openings due to inadequate adhesive
bonding may appear as smooth wood surface separations,
possibly darkened by the adhesive film, or as glossy surface
areas of adhesive with an absence of torn wood fibres.
SmartLam GL17 Design Guide 9