Balau vs CCA Treated Wooden Deck Durban

I often get asked about using balau as a substructure in a wooden deck. There are various pros and cons of using balau as a substructure in your wooden deck so I thought I would jot it down and in future I can direct clients here who want the ins and outs of using balau as a structure for your wooden deck.

Balau is a very good, hardy and durable wood to use in outdoor wooden decks and other outdoor projects. It contains toxins that limit insects eating it and it is high in resins and oils which naturally repels water and limits rot. All wood will eventually rot. It is just that some will rot quicker as they are less dense and less oily which means they will absorb water more easily, which remains in the wood, causing fungus to grow which breaks down the fibres in the wood 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 may take 15 years for this rot to start but it will happen and when it does repair work can run into thousands if not a complete deck rebuild. Joists are often difficult to access whereas deck boards are not.

On the other hand a piece of wood that has been chemically treated to prevent, or limit rot, will last a lot longer and a pre determined life span can be calculated.

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 copper, chrome and arsenate is introduced which then takes up the void created by the vacuum sucking the solution into the cells. The copper prevents 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 doesn’t leach out.

Balau is too hard and dense to treat. Pine is a commercially grown timber in South Africa which is inexpensive and very suitable for treatment as it is soft and takes up the solution of CCA successfully. 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. A correctly treated piece of pine to H3 will, as per SAWPA guidelines, last in excess of 50 years which is pretty impressive in comparison 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 in 15 years. Most of the pics I have documented here are of decks that range in age from 8 years to 15 years. But 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. So from an economic point of view it makes sense to use pine in place of other woods wherever possible.

One might now ask why is pine not used on the surface of a deck? Why is balau preferred?

Balau is a very stable wood and therefore expands and contracts less than pine. It is about twice as dense, knot free and doesn’t twist and warp as easily. Pine is soft and with the sun beating on the deck it will tend to crack, twist and warp more easily. 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 normally 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 in fact a few rand more per square metre than balau. Hence the reason to use correctly treated CCA pine as a substructure and balau as deck boards. 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 call us on 082 496 5444 or use the contact us form below.

Wooden Sundeck, Toti, Durban

Wooden Sundeck Installer Durban

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We built this wooden sundeck in Toti using CCA Pine, for the first time, as our substructure and decked it using balau deckboards. For a long time I have been using only balau as a substructure. But after some careful investigation I have accepted that a CCA treated pine substructure is as good if not better than a balau one.

The manufacturers of the solution that is used to pressure treat the timber guarantee their product for between 30 to 50 years depending on which manufacturer you use. Provided the company doing the pressure treatment treats it correctly and provided the correct Hazard Level (H level) is used in the correct application, the timber will be guaranteed against rot and insect infestation by the manufacturer of the solution. I will write another more detailed article on CCA pressure treatments, but for the purpose of this article you will need to know what it broadly means.

Wooden Sundeck Installer Durban

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H2 CCA Treated pine is good for roof trusses where it is not exposed to the elements such as rain. H3 treated is good for outdoors such as decks and H4 is good for in the ground or in contact with wet soil. H5 is good for in salty water and is normally a combination of CCA and creosote treatment. H2 is commonly sold off the shelf at most timber yards. H3 and H4 is more specialised so one needs to find a supplier who is regularly treating to H3 or H4. Under no circumstances should H2 be used as a substitute. It will rot within a few years. Simple. Do not use it in decks, keep it for the roof.

Wooden Sundeck Installer Durban

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In order to activate a guarantee against the manufacturer one would need to take photos of the deck going up ensuring that the correct H level is used, an audit process would need to be completed on the company treating the timber and the build would probably need to be registered with the manufacturer and possibly inspections conducted during the build. So although it is possible to activate a guarantee, it is not really practical as the substructure will go up in 2 days and the deck will be done in 5 days. However, if the manufacturer is willing to offer this sort of guarantee, then we can safely assume that the timber we are using will hold up to its promise. In a nutshell, H3 or H4 treated CCA Pine is suitable for a substructure for a deck and may very well outlast a balau substructure. I would not be too keen to use it as deckboards for two reasons. Although it won’t rot or get eaten by ants, it will expand and contract a lot more than balau which will result in checking, cracking, warping, bowing etc. over time. The second reason is that because it is half as dense, one needs to use a 32mm thick deckboard as opposed to a 19mm deckboard in balau. So twice as much timber is used and the cost is actually slightly more in pine per square metre than balau. So why not use balau in the surface? It is much better looking and much more stable (i.e. it remains flat for many more years).

Wooden Sundeck Installer Durban

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The cost saving in using CCA pine vs. balau in the substructure is great and this allows me to keep my prices low whilst still providing a quality product. The CCA Pine will last as long if not longer than the balau substructure if the correct H grade of CCA pine is used.

All areas that have pine exposed are clad with deckboards so that the pine is not visible. Balustrades remain full balau.

For a no obligation quote on wooden decks, balustrades, pergolas and any other outdoor timber construction, please complete the form below and I will get back to you.  Or you can call us on 082 496 5444.