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.
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.
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).
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.
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