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Ask an Expert

Forestry, wood processing & certification

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 planning to stack green sawn and finished dressed 150mm x 38mm spotted gum to dry for 12 months for an intended outdoor deck. I am concerned about sticker marking on the boards due to the drying spacers. Any advice ? I expect to lightly belt sand the boards when fixed in place, will this remove the intended marks? Is there a way to avoid the marks? Many thanks for your advice.

There is no guarantee that any technique will completely avoid sticker stain, but there are strategies that will help. Researchers recommend that (a) stickers should be dry wood (b) stickers should be approx 30mm wide by 19mm thick and (c) using grooved stickers may provide some extra advantage. To comply with these recommendations, ribbed kiln-dried hardwood decking would make suitable stickers, ripped down the middle to produce two stickers per decking board.

Q. Have had grey gums and spotted gums cut down approx 4 months ago. They have been lying where they were felled. They range from 300mm-600mm in diameter and lengths of approx 4 meters. Started ripping them into slab thicknesses of 55mm and then stacked them on flat concrete on 35mm blocks (1 meter spacings) then 20mm packers on top of each other inside a tin open door garage/shed, completely out of weather. Have sealed the ends with a primer. Question is, is this stacking method ok for drying the timber also how long should the timber be left to dry before being used to make furniture?

We think you've done all the right things so far, but the timber will need more time to dry. It's actually better to let it dry slowly than to hurry it up, because it's less likely to split if it dries slowly and evenly. So it's OK to have air moving through the shed, but not a good idea to let a hot wind blow through. As to how long it will take, we assume you have only just started converting the logs into slab thicknesses. At a guess we would say it needs another six to nine months, but the best way to be sure is to test it with a moisture meter. Another method is to weigh the timber at intervals - when it stops losing weight that means it has stopped losing moisture, but it's probably not practical to weigh such large pieces.

Q. Two Farm Management teams where Paulownia trees have now reached maturity -inside 20 yrs ,& where hundreds of dead , standing timber is currently 'available' -@ near Lismore, NSW and Pomona, Qld., are therefore 'awaiting milling'; timber users who now prefer Paulownia to most other 'softwood' species reckon P. is 'best for' making picture-frames, surfboards, wood canoes and boats.... Where can we be 'directed' for the milling of this ( Chinese) species'timber - as hardwood millers across Australia do NOT seem to want to ' know about-it'! ; RSVP AUTHOR: RESEARCH Specialist Joe A Friend.

We weren't sure whether the sawmillers you've approached weren't interested in processing the logs so you could sell the timber, or whether they weren't interested in buying the logs. It should be possible to find a sawmill to process the logs if you can get the logs to the mill. The NSW Forest Products Association (formerly Associated Country Sawmillers of NSW) should be able to help you to find a sawmill. They have a website at While we would expect a country sawmill to process the logs on a contract basis, they might not be interested in the timber if Paulownia is not what their usual customers want. If you are unable to find a sawmill in your area another option is to mill it on site using a Lucas Mill or similar. You can find out more by writing "portable sawmill" in your browser.

Q. I have blue gum trees on my property that I want to make into timber decking, who do I speak to to do this?

Producing decking from tree to finished product involves a number of steps. You will need to transport your logs to a sawmill in your area that has the ability to kiln dry and plane the timber, unless you are looking for a very rustic deck using green timber straight off the saw. With green timber you would expect significant shrinkage as the wood dries out, and some splitting due to drying stresses. If you don't want the decking to shrink after installation, and kiln drying is not available in your area, you could have it sawn and allow it to air dry before you build your deck. This would overcome the shrinkage problem and allow you to discard any pieces that split unacceptably while drying.

Q. I am a Year 9 student from Peter Moyes Anglican Community School. I haven an assignment which involves researching sustainable forestry. I have been having a bit of difficulty researching what processes are involved in sustainable forestry. What measures and procedures are undertaken in sustainable forestry?

Whether timber is produced "sustainably" or not is tested by assessing production against a range of criteria and indicators set out in standard documents, such as the Australian Forestry Standard (AFS). The assessment process is carried out by independent organisations which can then certify that the products come from properly managed forests. The great majority of Australian growers of plantation pine have achieved certification to the AFS, while a number of growers are also certified against the Principles and Criteria of the Forest Stewardship Council (FSC). Major Australian hardwood producers are also certified under these systems. You can find out more about the Australian Forestry Standard and download copies of a newsletter and fact sheets from the net at For more information about Australia's forests, refer to Australia's State of the Forests Report. The latest is the 2008 edition which can be ordered in hard copy, or downloaded from the net, at

Q. I was wondering is there is a database of moisture meters for obtaining the moisture content of wood that is certified for use in Australia? Or some way of telling whether a moisture meter is certified to give accurate measurements of the moisture content?

Research into the use of moisture meters is described in a report titled "The use of hand-held electrical moisture meters with commercially important Australian hardwoods" (Project No. PN01.1306) published by the Forest & Wood Products R & D Corporation. One of the outcomes of this project was to provide up-to-date species adjustment factors. When the moisture content of timber is tested the meter reading generally needs to be adjusted according to the species being tested. The research project found that when compared with oven dry testing (the most accurate method), resistance meters achieved an accuracy ranging from ± 1.5% to ± 3%. Dielectric surface meters are less accurate and were found to achieve an accuracy ranging from ± 3% to ± 6%. A resistance meter's accuracy (or at least a check on the correlation between meter reading and electrical resistance) can be carried out by using a check box. The check box has a standard resistance which should correlate with a particular reading on the dial of the meter.

Q. I am documenting some homes in a BAL 12.5 bushfire zone. We were interested in using Woodform's Pacific teak, but have realised that it is classed as an Eco Timber, sourced from the Solomon Islands. Are you aware of any suppliers of Pacific Teak who have had the ATIC certification?

Some teak production has achieved certification by the Forest Stewardship Council (FSC) but we are not sure that "Pacific teak" is actually teak. Some importers are applying the name "Pacific teak" or "New Guinea teak" to a timber more commonly known as vitex (botanical name: Vitex cofassus). This is a major commercial species of the Solomon Islands, so is probably what Woodform are offering. Vitex is certified under several different schemes and you can find our more if you enter "vitex timber certification" in your browser.

Q. In a commercial application how long does it take to dry a 25mm thick green hardwood board?

If you are thinking of air drying, it depends on the characteristics of the wood, its initial moisture content and the local climate. Research in the Philippines showed that 25mm boards dried from an initial moisture content of around 120% to around 15% in approx 80 days in the dry season. On the other hand, dense Australian eucalypts can take 6 months or more to air dry, again depending on initial moisture content and climate. Kiln drying 25mm boards from green commonly takes from 8 to 20 days depending on species. Since this is uneconomic it's usual in Australia to combine a few months of air drying with a kiln drying period of 2 to 7 days. In this way, air drying removes the bulk of water during the stage when it diffuses fairly rapidly, while kiln drying accelerates seasoning at the later stage when moisture is more difficult to extract.

Q. I've just milled a 200x200mm post and a 300x300 mm post both at 3m. I am getting conflicting reports of different people I ask as to the drying time and splitting risks. It is eucalypt so I expect some splitting but I'm not too bothered as long as it doesn't split in half. I have it stored under plastic on timbers. Do you know the normal drying time before being able to be used and techniques for best results.? Or even a good resource book that I could find to do the research myself?

The general rule for air drying large cross-sections with minimum degrade is to slow down the drying process. If the timber dries too quickly, so there is a big difference between the moisture content close to the surface, relative to the core, it will split. This is called the "moisture gradient". If your timber is stored under plastic, make sure there is some air movement and that it is sheltered from the sun and from hot, dry wind. Since wood dries more quickly from the end-grain than the side grain it's good practice to seal the ends with a wax emulsion. Aftek "Endcheck" is available for this purpose, marketed by Thomson White Australia, phone (03) 9791 8211. Your posts will also have a better chance of avoiding splitting if they don't contain the centre of the log, but since they are already cut your best strategy is to control the drying rate. You will find more detailed advice on the net if you write "air drying hardwood" in your browser.

Q. I have 4 trees that I think are iron bark hardwood that I was going to cut down. I was wondering if there was any value to them and who could do with the wood. I live near Dural, Sydney.

The problem with only four trees is that it might cost more to send a truck, plus labour to transport the logs to the sawmill, than the timber is worth. However, you could contact a hardwood specialist in the Sydney area to find out. We suggest AusTimber Supplies - for contact details visit their website at Failing that it would make excellent firewood when it has dried.


Did you know?

Australia’s native forests, timber plantations and wood products are net absorbers of greenhouse gases, sequestering 56.5 million tonnes of carbon dioxide in 2005, reducing Australia’s total greenhouse gas emissions by nearly 10%.