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Wood species & their properties

Like to know what wood to use building a pergola or framing a barn? How about the difference between tung oil and polyurethane as a floor finish? How to revive decking or deal with merbau stains? Or how to meet the building code or bushfire standards? Or ask about the environmental advantages of wood or forest certification?

Q. I am specifying a timber species for a house being documented in QLD in a bushfire BAL19 area. The client wants an external deck and stair that is low maintenance so I thought a naturally pale weathering species would suit. One of the FAQ questions highlights spotted gum as a good option for this circumstance due to its class 1 durability. Is that the main factor that dictates a suitable species to naturally weather and grey?

Durability is the most important quality if the timber is to be left to weather naturally. As a timber of Class 1 Durability outdoors above ground, spotted gum has a probable life expectancy of 40 years or more according to Australian Standard 5604. This depends somewhat on the severity of exposure, whether the stairs have joints that will collect water, and so on. You might give some thought to the way the treads are fitted to the stringers - if they are housed in, this creates a water trap and it's therefore good practice to coat the ends of the treads and the inside of the housing with a timber preservative, before the treads are installed. Alternatively the treads can be bracketed off the sides of the stringers with an air space between to allow the wood to dry after rain.

Q. We recently bought a new property with an open fireplace. The previous owner had also just refenced his entire boundary and kept all the old fence palings and posts. He advised us that we could use this for firewood. The fence slats (I'm guessing would date to the 1960's 70s.) Question: Is it safe to burn these fence slats in an open fireplace indoors, or are they like modern timber paling fences and treated with Arsenic and therefore unsafe to burn? They look extremely well weathered. Was CCA used on timbers of this vintage? How do you tell?

CCA was used from the early 1970's (and possibly earlier in parts of Australia). From a visual inspection it will be hard to tell whether the timber was treated if it's well weathered, although there are chemical tests which would identify preservative. One clue would be to know whether it is hardwood or softwood. Hardwood is unlikely to have been treated and the posts are possibly red gum or a similar durable hardwood. On the other hand if the timber is pine it would certainly have been treated otherwise it would not have achieved such a long service life. Hardwood would be practically knot-free, and relatively hard, whereas pine tends to be knotty and softer, so perhaps this will help to answer your question.

Q. I am looking into exterior timber batten screening for a property by the sea. Could you please recommend a suitable external grade timber for a seaside location? Three I have heard would be suitable are: Spotted Gum, Pacific Teak and Burnt Ash. Are there any pros/cons or would all three be equally suitable? Also, would you have any advice regarding anti-graffiti applications for timber products? For example any companies in Victoria that might specialise in this?

There is currently a trend amongst some importers to re-brand timber species with the prefix "Pacific", eg. Pacific jarrah, Pacific tallowwood, Pacific blackbutt, etc. We believe Pacific jarrah is a South American timber, while the S-E Asian timber nyatoh is sometimes marketed as Pacific blackbutt. However, we haven't been able to determine what Pacific teak really is. That's not to say Pacific teak is necessarily to be avoided, just that we don't know what it is. Presumably it's not real teak. Similarly there is no timber with the common name "burnt ash". So to be on the safe side we suggest that of these three, spotted gum would be the safest bet. It's rated Durability Class 1 outdoors above ground. Regarding anti-graffiti treatments, we don't know of any specifically for timber. We can only suggest you search the net and contact companies such as Sure Seal who claim to have state-of-the-art anti-graffiti products.

Q. Please can you tell me what the best hardwood is for building a 3.7m gate that will be painted.

Assuming the gate is fully exposed to the weather you will need a durable, kiln-dried species. Some softwoods are suitable, such as western red cedar and cypress pine. However, if you prefer hardwood suitable types include merbau, blackbutt, jarrah and tallowwood. Note that merbau has a high tannin content. For best results we recommend painting merbau on all surfaces with oil-based enamel paint rather than water-based acrylic. Tannin can bleed through water-based paint.

Q. I wish to use Australian White Beech to make a jewellery box. Is it acidic enough to tarnish silver?

A data sheet on white beech published by the Queensland Department of Agriculture, Fisheries & Forestry (DAFF) can be accessed via this link http://www.daff.qld.gov.au/29_5723.htm. The data sheet advises as follows: "Because of the natural acidity of this species, non-corrosive fittings and fastenings should be used." This suggests that white beech has a significant acid content. However, we are not expert on the causes of silver tarnish, and are not certain whether wood acid is likely to increase tarnish. Our understanding is that "tarnish" is formed when silver combines with sulphur to form silver sulphide, which is black. Wood has a very small sulphur content and the major acid in acidic woods is acetic acid, so it seems unlikely that contact with wood would accelerate the formation of tarnish. Sulphuric acid is used in papermaking, hence the recommendation that silver should be stored in "acid free paper" is to avoid contact with sulphur. You might wish to discuss this further with someone who has expertise in chemistry.

Q. We are chasing redwood. Your website show us there is redwood in Australia but I can't search supplier.

Thank you for pointing out that the Wood Solutions website advises Californian redwood is "readily available all over Australia". That advice is somewhat optimistic and in fact you are unlikely to find redwood in any timber merchant's yard. However, it was a commonly used joinery timber in the first half of the 20th century and you might find some being recycled. If not, red cedar would be a good match, ie. Queensland red cedar, surian cedar, etc. (not western red cedar).

Q. I am currently obtaining quotes to replace our exterior timber windows. We want to stay with timber and have so far had two quotes with two different opinions. We will be painting them on the exterior. One set of windows is very exposed as it does not have an eave above it. One company recommended the frame be made of western red cedar and the other recommended Vic Ash, both with merbau sills. I have done some research in Google and cannot make up my mind.

If we are comparing western red cedar with untreated Vic ash, cedar would be the better choice. Western red cedar is a dimensionally stable timber with a reasonably good natural resistance to wood rot, and is rated Durability Class 2. Untreated Vic ash is rated Durability Class 3 outdoors above ground, which in our opinion is not sufficient for fully weather exposed windows. However, preservative treated Vic ash may give service equal to, or better than, western red cedar depending how it is treated. Research suggests that LOSP treatement with an azole preservative gives best results.

Q. I was reading an article on cross laminated timber made in Europe and apparently it is made from grade C24 spruce. I was just curious what other timbers sourced within Australia have similar properties?

At present (Feb. 2013) cross-laminated timber (CLT) is imported from Europe, and several Australian distributors can supply imported product. You will find interesting stories on the net about local landmark CLT projects, such as the Forté apartments in Melbourne, set to become the tallest timber building of its type in the world. If it becomes viable to manufacture CLT in Australia, radiata pine seems the most likely material to be used.

Q. I have a door that I need to repair that I believe is made of "red pine". I need to replace a section where each hinge goes as it is being re-swung and also add a piece to the bottom of it where it has been cut off too short and roughly in the past. I was wondering if you can still buy this timber as I can't find any, if not then what would you recommend as the best timber to use to repair it.

"Red Pine" was the name given to Californian redwood when it was imported to Australia in large quantities for joinery during the first half of last century. You might still be able to obtain it from specialist timber suppliers or recycling yards. If not, Queensland red cedar or the imported species kalantas would be a good match.

Q. I am a designer and am currently designing external timber laser cut screens for aesthetic not structural purpose and researching having them made in China. Could you please advise what Chinese timber species they should be made from suitable for Australian Standards, NOT STRUCTURAL, DURABLE FOR EXTERNAL USE ONLY.

We don't claim a detailed knowledge of the Chinese timber industry, but we understand that cypress grows in various parts of China where it is known as bai mu, or 柏木 in Chinese characters. The botanical name is Cupressus funebris and it is also known by the common name "funeral cypress". Tests by the Chinese Academy of Forestry rated Cupressus funebris as "very durable" with regard to rot resistance, so it should be suitable for weather exposure in Australia, although we have no record of its use in this country. If bai mu is not available, teak would be suitable and it is generally available throughout Asia.

WoodSolutions

Did you know?

About 16% of Australia’s 147 million hectares of native forests are in nature conservation reserves.