Building a timber deck or pergola?

Before you start building your own deck or pergola read on to understand some of the most commonly asked questions asked by those who have gone before you...

 

 

The selection of timber to be used for an outdoor situation such as a deck or pergola, you must take into consideration the exposure to the natural elements. Therefore, selection of species that are durable for the application as well as being easy to work with, should be the basis of your criteria. For example;
• Posts in ground should be In-ground Durability Class 1 species or preservative treated softwood to Hazard level 5 (H5)
• Above ground posts should be of an Above Ground Durability Class or preservative treated softwood to a H3 level.
• Other structural elements such as decking materials, joists etc. should be Above Ground Durability Class 1 or preservative treated softwood to H3.
• If you are selecting hardwood for decking purposes it is recommended that it be a seasoned (usually kiln-dried) product of an Above Ground Durability Class.

 

 

 

In some cases Yes! Timber with a natural low durability, regarded as a Durability Class 4, such as softwood (pinus species) can be used in all situations providing the sapwood is treated to the relevant hazard level (H) required by it's application.

Hardwood species with sapwood present must also be treated to the required hazard level. The main area of durable timber on hardwood is usually found in the heartwood which is extremely hard to preservative treat - therefore it relies mainly on it's natural durability. That is why it is good to know what species you are purchasing or using, you can design correctly for its use.

Note: CCA treated timber should not be used for domestic decking or handrails. It is suitable for use for deck joist, bearers and posts.

 

 

Timber is a natural product and if left unprotected and exposed to the natural elements such as, the weather and UV radiation, for extended periods of time, the surface will discolour and checks and cracks may form.
To protect and extend the life of the timber product it is appropriate to use a good quality timber finish such as paint or timber stain. These will need to be applied and maintained correctly over the life of the structure - refer to paint manufacturers instructions.

Hint: Pale or pastel colours are considered to perform better as a protective coat.