- Sundeck design
- Steel, concrete, timber
- The timber used
- Sealing a sundeck
by Garrick Dunstan - The Wood Joint
Although timber decking has always been popular as a method of
construction it is becoming more and more popular as trends move
towards more natural methods and finishes in construction while
considering environmental impact and the foot print building creates.
Provided timber is sourced from sustainably managed forests, timber
Sundecks are of course as natural as one can get.
A timber sundeck adds value to your property at an affordable cost,
in comparison to other construction methods, and, if well looked
after, can last a lifetime. They compliment our outdoor lifestyle
in South Africa and offer years of enjoyment.
Steel, concrete, timber
The choice between using concrete, steel or timber in your sundeck is a
complex choice with many variables to consider. One should take into account
the following when making a decision: -
Ease of build
It is often best to research this independently based on your unique requirements and conditions.
The timber used
There are a number of different types of timber available which have been carefully
selected to fit your taste, your pocket and the environment we found ourselves in.
The most common timbers used are: -
This must be CCA Treated to at least an H4 level if outdoors and exposed to the elements.
CCA stands for Copper, Chrome and Arsenic. The copper prevents algae growing on the
timber caused by dampness. Algae causes rot by breaking down the fibres in wood.
Hence the wood can get wet without rotting. The arsenic prevents insect infestation
and the chrome binds to two to prevent them from leaching out of the timber.
The amounts of chemicals present in the timber do not affect humans, animals or
plants in any significant way and it is therefore safe to humans, plants and animals.
The level of treatment (H4) refers to the strength of the solution and the pressure at
which it is forced into the timber.
Sourced from South East Asia this timber is the most cost effective hardwood. There is
no need to pre treat it as it is naturally resistant to rot and decay due to the high
levels of oils and resins present in the timber. Balau decking boasts a fire rating of
Class A which is the same as concrete or steel.
Garapa, Massaranduba, Keruing:
These are all equally matched to Balau in terms of durability and workability but are
slightly more expensive. It is therefore common to use Balau as the sub structure with
these timbers as the deckboards and visible components of the sundeck.
It is not advisable to use pine as your substructure with a balau or similar hardwood as
deckboards as the timbers expand and contract at different rates and can cause screws to
either break or pull out.
When taking into account what timber to use one must remember that the cost to install the
deck is often the greater percentage of the total cost and the benefits of paying slightly
more to get a balau deck are far greater than the cost saving of using pine.
Composites are manufactured deckboards using largely re-cycled plastic. They are
available in a range of colours. The argument is that they are more enviro-friendly than
wood and that installation is easier, and therefore less expensive to install. They are
normally more expensive per square metre of deck in terms of materials and it is argued that
they are maintenance free. However they cannot be sanded once they are installed as they are a
plastic composite and should scratches occur on the surface they may prove difficult to remove.
They are installed using a CCA Treated Pine batton or joist and the substructure is
normally pine. They are however being installed successfully and should not be ignored.
Sealing a sundeck
The myth that a timber sundeck is expensive to maintain is unfounded, provided it is
installed using good quality timber and construction methods are sound. If finished with
the correct sealer, maintenance can be reduced to a minimum and maintenance intervals can
A common mistake that is often made is to coat the deck with a coating that does not penetrate
the deck surface but rather dries on the surface. With the hot African sun beating down on the
deck the horizontal surfaces often start to crack and flake. Using a penetrating timber
preservative avoids this occurring and reduces labour costs at scheduled maintenance intervals.
Screw holes should always be filled with an epoxy to avoid them “popping” and to avoid water
penetrating the timber through the screw hole. One must remember that water penetrates wood
largely from the end grain and therefore any screw holes left unfilled will allow water to
easily penetrate the timber. End grains should also be well sealed to avoid this.
After taking into account your unique requirements and environment it is difficult to argue
that a well constructed timber sundeck, using quality timber from reputable suppliers will
not add value to your property while providing many years of enjoyment.
The warmth of wood cannot be replicated by other building materials.