Inspection of
timberwork and fasteners
Termite inspection
Why is
effective finishing and maintenance important?
If timber is left unprotected, weathering will result in colour change,
a loosening of the timber fibres and a gradual wearing away of the
surface, from the combined effect of exposure to water from rainfall
and ultra-violet (UV) radiation in sunlight (please refer
to the note at left regarding preservative treatment and weathering).
Unprotected timber will swell and shrink as moisture is absorbed and lost in
response to local changes in atmospheric humidity or direct wetting, causing
surface checking which allows subsequent rainfall to penetrate deeper
into the decking. The UV
radiation in sunlight will gradually turn the surface of unprotected timber
to a silver-grey colour.
Uncoated timber remaining damp for extended periods, or in areas of high
humidity, may also develop dark discolouration due to the presence of
surface mould.
Effective finishing and regular refinishing
and maintenance of a timber deck will add
years to its life and improve the performance and enjoyment along the
way.
Finishing
Decking is particularly susceptible to weathering damage from exposure to
sun and rain and particular care
should be taken in its initial finishing and refinishing, as part of a
maintenance program, to ensure performance and
longevity.
With its thin section, decking is likely to
experience a greater reaction to changes in atmospheric moisture.
Boards will tend to swell, as they absorb moisture in wet weather and
shrink as they dry out, producing small cracks (surface “checks”), and
possibly cupping. As decking is oriented with its larger dimension
horizontal, it is also more exposed to the effect of direct sunlight
and more likely to absorb moisture as water pools on its surface.
Natural finishes should be commercial formulations meeting the requirements
AS 1607.
Raw Linseed oil, or mixtures containing raw linseed oil, can encourage mould
growth in timber and should not be used as a natural finish unless contained
in a commercial product containing mould inhibitors. Mould growth will
discolour the timber and removal of mould is difficult. It is often
necessary to scrub the decking with a timber cleaning solution and stiff
brush before re-coating.
Decking which may be subject to pedestrian traffic when wet, may become
slippery and difficult to traverse or hazardous and should not be coated with any finish that leaves a gloss coating on
the surface.
In areas of high temperature, pale coloured finishes are recommended, as
they reduce heat absorption and the possibility of board distortion and premature deterioration
of the finish.
Please note that the following advice on application of decking
finishes is for general advice only.
Each product type and potentially brand will have its own characteristics
and our advice is to obtain (through download from the manufacturer or
from your local supplier), understand and follow the detailed surface
preparation and application and maintenance instructions developed
specifically for the characteristics of the product by the manufacturer -
following their instructions will deliver the best results.
Please click here for advice on
Which decking finish should I use?
(FAQ Decking Finish Return)
Application of penetrating oil and stain finishes
Remembering that the decking has been sealed with a preparatory oil or stain
coat, all round including liberal application to the end grain prior to
laying, refer now to the manufacturers instructions as to whether a second
or even third coat is recommended.
Once the decking has been laid, if recommended by the manufacturer,
apply another coat of the chosen finish to the exposed surface - some
manufacturers recommend only one coat initially and some recommend up
to three if the timber will absorb it.
The finish should be applied to a run of three to four adjacent boards along
the full length of the deck, and not across the width. The gap between the
boards can then be used to separate each run, so as to avoid overlapping of
the finish, which may result in a patchy appearance on the overlap.
Before applying finish to the boards, use a paint
brush to apply finish to the joints where the board ends are butting up, so
that the finish runs down between the cut ends and soaks into the porous end
grain. Pushing sealer down into the joint will help to seal the end
grain and reduce the cracking of board ends resulting from wetting and drying
and deterioration from moisture soaking into the end grain.
Note that excess finish pushed into the joint and applied to the boards may
drip onto the surface below. If you do not want drips of excess finish to
affect the area below the deck eg if there is a patio below the deck you can
protect the area with drop sheets (or similar).
Only apply as much finish as the timber will absorb. Do not load the
applicator too heavily and push the finish well out along the timber.
Once you have completed the run of boards and while the finish is still
wet, brush over the coated area, first into the gap between the boards
to apply some finish to the edges then over the face of the boards to push the finish into the surface. After
allowing a short time for the finish to absorb, but while it is still
wet, brush over the surface to even out any patchiness resulting
from irregular application or variations in the rate of absorption into
the timber.
If more
finish has been applied than the timber will absorb in places, brush any excess out
along the boards or remove by wiping with a soft cloth.
A common
problem with the application of stain finishes, is that the stain is applied
too heavily and is not completely absorbed into the timber as it should be.
"Overloading the surface” by applying a lot more finish than can be absorbed
will cover the grain of the timber, and produce a stronger colour than
intended when the stain was selected. Overloading often occurs in the
belief that more finish will provide better and longer lasting protection.
Decking stains which have become over-applied, producing a “surface
coating”, may be glossy or uneven (blotchy), slippery and unstable and
may weather off unevenly.
We would advise
against coating the decking section by section along its length as this
is likely to result in overlapping of the edges of the previous
section, which will result in irregular, more opaque strips at the
overlaps.
As an oil finish penetrates more readily than a stain finish, it is likely
that more oil would be required for the same area and unlikely that an
uneven appearance would result with reasonable care in application.
Refer to the manufacturers recommendations as
to whether a third coat would be beneficial and if recommended, follow
the manufacturers instructions carefully for best results. With
dense timbers a third coat may not penetrate and finish may remain on
the surface.
Application of clear
film building decking finishes
Clear film building decking finishes can also be used to protect decking
from weathering, however be careful to read, understand and adhere to the
directions particularly in relation to any requirements for initial
weathering, washing of decking surface and use of preparatory coats.
Film building finishes, properly prepared, applied and maintained, as an
integrated system, can give good service over a long life. Applying film
building finishes without attention to the whole system may result in
unsatisfactory performance and reduced life.
Application of paint finishes
As mentioned on the "Materials" page under
Finishings, we would suggest the use of a penetrating oil or stain
finish or specialty clear film building decking finish rather than paint for protecting decking, as paint can become slippery when wet and as the protection relies on the paint
film remaining intact. Decking is subjected to foot traffic which can damage
the paint film, allowing moisture penetration which can lead to
deterioration of the decking, as moisture which is absorbed cannot readily
escape and may also lead to further damage to the remaining paint film.
If a
paint finish is required, seek advice from your supplier during your
planning stage and before commencing construction, on suitable paint
products and finishing techniques to seal and
finish decking. Normal exterior paints
are unlikely to be suitable for use as a decking paint.
Finishing of structural timber
Remembering that any timber-to-timber interfaces have been sealed during
construction, with an
appropriate sealing coat to prevent trapped moisture causing accelerated
deterioration, preparatory and finish coats can now be applied to protect
structural timber from the effects of weathering.
Discuss with your paint supplier, appropriate products and correct surface
preparation and application techniques for sealing, prime and finish coats
to gain good performance and longevity from your finish coat.
Care of your deck
The main enemy of an exposed timber deck is moisture. Except for the effects
of weather over which we have no control, wherever possible keep your deck
dry.
Decks should not be hosed down or subjected to regular wetting from
irrigation systems. Pot plants should be placed in drip trays standing on
small cleats clear of the deck. Any leaf material and debris should be
broomed off at regular intervals.
Maintenance
To achieve
satisfying long-term performance from your timber framed deck, perform
regular and effective maintenance at appropriate intervals, including
re-application of the decking finish and a physical inspection for
deterioration of timberwork and fixings and termite activity .
Refinishing
Oil or stain finishes should be re-applied while the timber retains some
water repellency. Water ‘beading’ on the surface indicates that the water
repellency is effective. Water absorbing into the surface indicates that the
water repellency is being reduced or has been lost.
Decking in weather-exposed or severe
conditions will require reapplication of the decking finish at shorter
intervals than in protected conditions. Carry out preparation and reapplication in accordance with manufacturer’s recommendations.
As mentioned previously on the Materials page under "Finishings", in "average"
conditions, you should expect protection for 9 to 12 months from oils and 12
to 18 months from stains. In severe conditions, such as around pools,
recoating is likely to be necessary at shorter intervals. For best
protection, finishes should be reapplied in the period before the most
severe weathering conditions eg before the heat of summer or before the
wetter part of the year.
Generally, decking which has had the greatest weather exposure will be
“drier” and may absorb more of the finish during recoating, with less (or in
some cases negligible) absorption in protected areas. Make an allowance for
this varying absorption when re-coating so as to avoid overloading the
surface in the protected areas.
Decking Oils generally contain UV inhibitors, which may slow the natural
greying of timber over time. If decking timber has begun to turn a silver
grey, the colour can be restored by the application of a coloured decking
stain, which is best applied at appropriate intervals before a strong grey
colour develops. Greying of timber will still occur under a roof, however it
will take longer as the UV exposure is less direct.
It is important that re-application of a paint finish occurs while the
finish is in good condition, as water pooling on the horizontal surface of a
deck can penetrate a damaged finish accelerating deterioration of the finish
and decking.
A damaged finish can require intensive preparation in terms of sanding and
repriming.
Some raising of the grain may be experienced on the exposed face of timber
decking from weather exposure. If this occurs, a moderate hand or
machine sand will remove the raised grain in the affected areas. Take
care that machine sanding does not damage the protective finish on your
fixings - this is a good reason for using stainless steel nails.
Regular re-application of the finish coats, as recommended, will act to
protect and nourish the decking and reduce the incidence of raised
grain.
If the timber has
developed black spots (mould) or has greyed from the effects of weathering,
the deck should be cleaned with a commercial deck cleaning and reviving
product - application, protection of adjacent surfaces and plants and period
required before applying the intended finish shall be as recommended by the
manufacturer. We would suggest using the deck cleaner produced by the
manufacturer of the intended finish.
Application of maintenance coats
When applying decking oil or stain as a maintenance coat use a similar
technique as for the initial coat.
The finish should be applied to a run of three to four adjacent boards along
the full length of the deck, and not across the width. The gap between the
boards can then be used to separate each run, so as to avoid overlapping of
the finish, which would result in a patchy appearance on the overlap.
Before applying finish to the boards, use a paint
brush to apply finish to the joints where the board ends are butting up, so
that the finish runs down between the cut ends and soaks into the porous end
grain. Pushing sealer down into the joint will help to seal the end
grain and reduce the cracking of board ends resulting from wetting and drying
and deterioration from moisture soaking into the end grain.
Note that excess finish pushed into the joint and applied to the boards may
drip onto the surface below. If you do not want drips of excess finish to
affect the area below the deck eg if there is a patio below the deck you can
protect the area with drop sheets (or similar).
As with the initial coat, only apply as much finish as the timber will absorb. Do not load the
applicator too heavily and push the finish well out along the timber.
Once you have completed the run of boards and while the finish is still wet,
brush over the coated area, first into the gap between the boards to apply
some finish to the edges then over the boards to push the finish into the surface. After
allowing a short time for the finish to absorb, but while it is still
wet, brush over the surface to even out any patchiness resulting
from irregular application or variations in the rate of absorption into
the timber.
If more
finish has been applied than the timber will absorb in places, brush any excess out
along the boards or remove by wiping with a soft cloth.
A common problem with the application of stain finishes, is that the stain
is applied too heavily and is not completely absorbed into the timber as it
should be. "Overloading
the surface” by applying a lot more finish than can be absorbed will cover the grain of the timber, and produce a stronger colour
than intended when the stain was selected. Overloading often occurs in
the belief that more finish will provide better and longer lasting
protection. Decking stains which have become over-applied, producing a “surface coating”,
may be glossy or uneven (blotchy), slippery and unstable and may weather
off unevenly.
If a paint system has been used, take care not to damage the paint film,
repair any damage as soon as it is apparent and re-coat the finish while in
good condition.
Inspection of
timberwork and fasteners
Undertake regular competent structural inspection of the underside of
the deck (eg annually) for signs of deterioration of the footings,
footing brackets, structural and decking timber and fixings.
Please note: If you do not feel that you are able to perform
suitable inspections we suggest that you employ the services of a
licensed professional building inspection service to perform the
inspections and provide you with a written report of the condition of
your deck and any maintenance which may be required.
Particular attention should be given to:
-
connection points and cut ends of
timberwork where trapped moisture may cause accelerated deterioration
eg housed/checked joints, cut ends which are butted up to another
surface and pole plate to house connection, and
-
bolts and brackets, which are the
primary means of support of the decking subframe, deterioration of
which, over time, can lead to failure under extreme load eg bolts
which fasten bearers to the face of posts, joist hangers which
support joists at the bearer and bolts or screws which fix a pole
plate to the house framing.
Test timberwork by poking with a metal probe
such as a screwdriver and tapping with a light hammer at connection
points, cut ends or any area which has a distorted surface - expanded
or collapsed appearance or which does not appear "sound". If
normally hard timber has become soft and spongy or does not sound
solid, it is likely to be suffering deterioration from decay or termite
attack (refer Termite Inspection below).
Minor deterioration from decay may be treated by improving ventilation
and runoff of moisture and using paint on or injected timber
preservative to reduce further deterioration. Significant
deterioration is likely to require replacement of affected timberwork.
Safety Tip: Restrict access to the deck while you are carrying
out any inspection. If you have found significant deterioration,
leave the area immediately and restrict access to the deck until you
have had the structural safety of the deck confirmed and affected
timberwork repaired or replaced.
Test bolts by tapping out sufficiently to see if the shank of the bolt
has corroded. Similarly, unscrew screws sufficiently to see if
the screw has corroded. Inspect joist hangers for surface and
edge corrosion and to ensure the heads of connecting nails are intact -
it has been a practice for high strength connector nails to be replaced
by lower strength flat head nails which can fail under load.
Minor corrosion may be treated by coating the shank of the fastener
with grease to stop further corrosion. Replace any fasteners
which have suffered from significant corrosion which has reduced the
effective shank diameter and load bearing capacity.
Safety Tip: Restrict access to the deck while you are carrying
out any inspection. Do not remove the fixing completely
initially, only check one at a time and if necessary treat and/or
replace each fastener before moving on to the next. When testing
and if removing a fixing for treatment or replacement, provide an
alternative, effective, means of support such as a prop. If you
have found significant deterioration, leave the area immediately,
restrict access to the deck and provide an alternative means of support
until all of the affected fixings have been replaced.
Termite inspection
Undertake regular inspection of the underside of the deck (eg
six monthly) for signs of termite activity, such as termite tunnels or
trails or hollowed out timberwork, using probes and a small hammer.
If any termite activity is found, create the least disturbance possible
and contact your pest control professional immediately for urgent
treatment.
In addition, have your deck professionally inspected at regular
intervals, as part of your home inspection. Regular professional
inspection of your home is likely to identify any activity in the early
stages. By the time damage has become apparent to the untrained
observer, it may be significant and costly to repair.
Ensure that the pest controller performing any inspection or treatment has completed
the relevant timber treatment modules of the pest treatment
certification process.
Further information on termite
control, suitable inspection intervals and choosing a reputable pest controller can be
obtained from the Australian Pest Controllers Association
( Ph: 1300 660 200
Web: www.pestcontrol.org.au
).
