Yes, emphatically, YES!. at Paul's Decking and Pergolas we will only use H3 treated timber above ground and H4 treated timber in ground as well as ONLY galvanised or stainless steel fixings.
We are currently doing a re-deckling job for a client in Burnside. When we took up the old decking boards we came across a section of the frame that was (note past tense) supporting a step in the deck. Clearly the previous builders ran out of treated timber and elected to finish the job with a small piece of non treated timber. This piece of framework was also at the edge of the deck meaning it would be subjected to more weather than the internal sections of the frame. After just 6 years here is what it looked like.
Note the difference between the rotten (non treated) timber in comparison to the rest of the timber in the frame which is treated.
So what exactly do the 'H' designations mean when it comes to treated timber?
According to Australian Treated Pine there are six main levels of treatment.
H1 – Designed to minimise the chances of an attack by insects and termites, H1 treated timber is best used in well-ventilated places where the timber will be kept off the ground and isolated from weather conditions, including rain or any moisture. Its typical uses are framing, flooring, furniture and interior joinery.
H2 – Similar to H1, H2 is also designed to minimise the risk of an attack by insects and termites, and can be used in well-ventilated places where the timber will be kept off the ground and isolated from weather conditions, including rain or any moisture. H2 however, is more resilient and doesn’t need to necessarily be kept in a well ventilated area. It does however need to be prevented from wetting. Its typical uses are framing, flooring and any other dry situations.
H2F – Also designed to minimise the risk of an attack by insects and termites, H2F must be protected from wetting, and is commonly used for framing (envelope treatment) and used in dry situations south of the Tropic of Capricorn only.
H2S – Similar to H2F and previous levels of treatment, H2S protects timber against insects and termites, but it also allows for subject to periodic moderate wetting. You will find H2S commonly used in the treatment of LVL/Plywood (glue-line treatment) used in dry situations south of the Tropic of Capricorn only.
H3 – The next level of treatment, H3 is suitable for use in applications where the wood is kept off the ground and exposed to weather conditions and periodic moderate wetting. Most commonly you will find this treatment being used in weatherboard, fascia, pergola posts (above ground), window joinery, framing and decking.
H3A – This level of treatment is designed to be applied to products that are predominantly in vertical exposed situations and intended to have a supplementary paint coat system that is maintained regularly. The most common uses for H3A are found in fascia, bargeboards, exterior cladding, window joinery, door joinery and non-laminated verandah posts.
H4 – This is the first level of treatment that is suitable for use in applications where the timber is in contact with ground or is continually damp. H4 is designed to minimise the likelihood of attack by insects, including termites, and radical decay where a critically important end use is involved. Typical uses for H4 include fence posts, greenhouses, pergola posts (in-ground) and landscaping timbers.
H5 – A stronger level of protection, H5 is suitable for use in applications where the timber will come in contact with the ground or fresh water. Other than protecting against the likelihood of attack by insects, H5 also offers protection against extreme decay. Common applications that call for H5 include retaining walls, oiling, house stumps, building poles and cooling tower fill.
H6 – As protection against the highest level of hazard, H6 is appropriate for applications where the timber will be in prolonged contact with sea water. H6 is designed to minimise the likelihood of attack by marine borers and extreme decay. You tend to find H6 used only on boat hulls, marine piles, jetty cross bracing and other similar applications.
At our Burnside job today we also came across the result of non galvanised fixings used in wet areas. Here is another picture, The nails all over this deck looked just like these ones.
Treated pine should last between 15 and 20 years, BUT only if it is fixed with galvanised or stainless steel fixings. Otherwise the fixings simply rust out and the frame falls apart. Our client is now having to replace his entire frame because the builders did not use weather appropriate fixings and they are all badly rusted.
So anytime you, or a contractor working on your behalf is working with wood outdoors make sure that appropriately treated timber and rust proof fixings are being used. Otherwise like our client you may well be replacing the whole thing in no time at all!