Frequently, I am asked about using Balau instead of Pine, as the substructure in the construction of a wooden deck. There are various pros and cons of using Balau and therefore I thought I would write about it and in future I can direct clients here who have this same query – that of using Balau as a sub structure for their decks.
Balau is a hard wood; hardy and durable and recommended for use for building outdoor wooden decks and other outdoor projects. It contains toxins resulting in limiting wood-eating insects. It is high in resins and oils which naturally repels water and limits rot. All wood will eventually rot; some will rot quicker as they are less dense and less oily which means they will absorb water more readily, which remains in the wood, creating a good breeding ground for fungus to grow which breaks down the fibres in the recommended food and is commonly called rot. This is a simplified explanation but I think it delivers the message accurately. Water doesn’t cause rot. Fungus, as a result of water and sunlight, causes rot.
Balau therefore will rot and I have started documenting some pics of rotten joists that I have come across in my repair work of wooden decks. It can take 10-15 years for this rot to start but it will happen and when it does repair work can run into thousands and is hence not cost savvy. In this instance, a complete deck rebuild will be required. Joists are also often difficult to access whereas deck boards are not.
Conversely, a piece of wood that has been chemically treated to prevent, or limit rot has a longer life span and therefore, this pre-determined life span can be calculated ahead of building.
CCA Treatment is a process of pressure treating SA pine. A vacuum is created in a chamber that contains the pine and a solution of chrome, copper and arsenate is introduced which then takes up the void created by the vacuum sucking the solution into the cells. Copper prevents the fungus growing which in turn prevents rot; the arsenate keeps the insects away and the chrome binds the two to the wood so that I don’t leach out.
Balau is too hard and dense to treat. Pine however, as a commercially grown timber in South Africa, inexpensive and very suitable for treatment as it is soft and takes up the solution of CCA successfully, is perfect for your deck’s sub structure. There are various different Hazard Classification or H classifications. Basically H2 is good for indoors (roof trusses etc.) H3 for outdoors exposed to the elements, H4 for in constant contact with wet soil. H5 for submersion in fresh water and H6 for submersion in salt water. Correctly treated pieces of pine to H3 will, as per SAWPA guidelines, last for longer than 50 years which is most impressive compared to a piece of Balau that comes with no fixed life expectancy. A poor quality piece of Balau may start to fail within 5 years whereas a good quality piece may only start to deteriorate in 15 years. Most of the pics I have documented here are of decks that range in age from 8 years to 15 years. Generally speaking I have found some rot setting in all the decks of 15 years or older.
S5 (SABS Structural grade) Pine is considerably cheaper than Balau structural timber, hence from an economic point of view it makes sense to use pine in place of other woods where possible.
Why is Balau preferred for the surface of a deck as opposed to Pine?
Balau is a most stable wood and therefore expands and contracts less than pine. It is +- twice as dense, knot free and doesn’t twist or warp as easily. Pine is soft on the other hand and with the sun beating on the deck it will tend to crack, twist and warp more easily. It will also pit if heavy objects drop onto the surface. To use pine as a deck board one needs to use a 38mm board as opposed to a 19mm board in Balau (twice as much wood), also pine deck boards are usually manufactured from S7 as opposed to S5. S7 refers to the number of knots per square inch (or centimetre) and is therefore a lot more expensive than S5. The cost of pine deck boards is a few Rand more per square metre than Balau. Therefore, correctly treated CCA pine as a substructure and Balau as deck boards makes the perfect union. Again pine doesn’t work well in balustrades because twice as much wood needs to be used at S7 grade.
For a free, no obligation quote on your sun deck, pool deck, balustrades, pergolas etc., please contact me, Garrick Dunstan, on 082 496 5444 or use the contact us form below.