Ask an Expert

Ask an Expert

Other topics

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 looking for a buyer of high quality wood in large quantities. We have in our legal possession about 80,000 cu. feet of Logs of Ghanian Rosewood (Dalbergia spp) which can be shipped immediately from India with export document approval. Part of the consignment is being cut into logs. A test certificate and sample can also be dispatched. Can you please intimate me contact details of such suppliers.

Our service is limited to providing technical advice and information about wood products and we are not involved in buying and selling timber. Perhaps the Australian Timber Importers Federation (ATIF) would be a more appropriate organisation for you to contact. They have a website at www.atif.asn.au which will give you more details.

Q. I am specifying a project where we have a concrete wall formed up with timber. We are wanting the timber form to leave a wood grain impression on the concrete when it is removed. Is there a hard wood that you could recommend that will not stain the concrete when it is removed or splinter for that matter. Also, can you tell me what timber is general used to form up concrete?

A hardwood won't leave much of an impression in wet concrete since hardwoods don't have prominent growth rings. You need a softwood with a pronounced growth ring structure, unless you actually want a relatively plain effect. The usual timber is off-saw oregon, which leaves a textured finish as well as the imprint of the growth rings. It's most important to use an effective form release agent so the concrete doesn't stick to the wood and spoil the effect. You will find a number of examples on the net if you write "wood grain in concrete" in your browser.

Q. I am about to list my house, a cedar clad weatherboard, and want to highlight to prospective buyers all the benefits of cedar cladding over brick veneer, rendered blueboard, colourbond metal, etc. Are you aware of a document that I can read that lays this out? Also, I would be interested in cost comparisons of various external claddings on a sq meter basis, ex. is cedar cladding more or less expensive than brick, blueboard, etc. I have about 300 sq meters of cedar cladding (2,000 lin meters) and am curious what it would have cost to do in brick, blueboard? Thanks for any guidance.

Western red cedar has excellent insulating properties. The performance of insulation is usually quoted in terms of its R-value, ie. thermal resistance. The R-value of 19 mm western red cedar cladding is 0.2 in metric units. The R-value of brickwork depends on the density of the bricks – the denser the bricks, the lower the thermal resistance. For example, common bricks 90 mm thick with a density of 2030 kg/m3 have an R-value of only 0.054. Realistically the R-value of the total wall should be compared – obviously a brick veneer wall with insulation in the wall cavity will perform better than a single skin of 90 mm brickwork. Regarding a cost comparison, this is more complex since the only valid comparison must include labour. You would have to obtain a quote from a contractor to compare the different systems, but generally speaking timber cladding is much quicker and cheaper to install than laying bricks.

Q. We are trying to determine if the following Standard BS-3823-BW-BR for Hickory Shafts are heat treated and accepted in Australia? Your help on this matter would be much appreciated.

Timber that is free of bark and has undergone a heat treatment approved by the Australian Quarantine & Inspection Service (AQIS) within 21 days of export, is considered to be effectively treated against pests exotic to Australia, except where AQIS has identified a specific quarantine concern. Kiln drying has a long history of commercial usage and is known to be an effective treatment for insect, fungal and nematode timber pests. In recognition of its long history of commercial use and standard kiln operating procedures, kiln drying certificates are acceptable to AQIS as validation of this treatment. We assume you are intending to import hickory shafts into Australia. If they have been kiln-dried within 21 days of export there should be no problem. Aside from kiln drying, we doubt that hickory shafts produced to the British Standard would normally be heat treated. This is something you would need to take up with the producer in the country of origin. Further information about the requirements for importing timber products can be obtained from the AQIS office in your State.

Q. I have a cabinet which was made around 2001. It is rimu veneer on ply. It has started to be eaten by pinhole borer or similar (small 1mm holes with floury powder. I live in the Illawarra in a house being renovated. I am using a lot of recycled mixed hardwood species. I also have a lot of big river timbers armour panel spotted gum ply. When milling recycled timber I notice the occasional longhorn beetle appearing and a reasonable amount of pin hole evidence. I have not noticed any powder around pin holes in hardwood. I understand that the lyctid borer is most likely and that it only eats softwood and not old seasoned timber. I also understand that it is unlikely to reinfest old seasoned hardwood however it may emerge from time to time. I assume my ply is over mixed softwood species. Is it likely that the rimu cabinet has been infested from borers originating from surrounding recycled hardwood or from within the softwood ply? Can I easily treat the rimu ply (there are many holes to inject if practicable) or should I get rid of it. It has been left unsealed since its construction. Is the infestation in rimu ply likely to spread to recycled HW or big river armour panel ply? Should I be taking any precautions with the recycled HW? I understand that the Big River Ply should be treated if it has any sapwood?

It does sound like a classic case of Lyctid borer attack (1 mm holes and dust like flour or talc powder). These borers only attack hardwoods and then only the sapwood portion. The sapwood is the outer part of the log and is usually a pale creamy-white colour, which distinguishes it from the darker coloured heartwood in the central portion of the log. If the timber happens to be a light-coloured wood it might be hard to differentiate the sapwood from the heartwood, but with the darker red-brown timbers it's obvious. Although the sapwood of rimu is susceptible to Lyctid attack it seems odd that it would be initiated after such a long time. Presumably the cabinet is sealed with a coating, but perhaps not on all surfaces. As to where the borer came from, it's always hard to say. Lyctid borers are everywhere in the environment and can attack susceptible timbers at any time if they are unsealed or untreated, although this usually happens with the first few years. Regarding treatment, you could try injecting an insecticide into all the holes, but if there are too many to treat you could either take the cabinet to a pest control company and have it fumigated or, if it is not particularly valuable, discard it. Infestation can only spread to other timbers if (a) they are hardwoods and contain a portion of sapwood and (b) have an unsealed surface or edge that allows borer entry.

Q. We are using 12mm marine grade ply as an internal wall lining and at the base of the wall we would like to continue the lining in a curve (outside radii 160mm)that then tucks under a mezzanine situation and continues on as a ceiling lining. We want this to all 'read' as the same finish. Our understanding is that 12mm ply sheet cannot be curved at this radius - can you suggest a solution?

It would not be possible to bend 12mm plywood to a 160mm radius in a cold bend. Bending over a heated form might be possible but today's joinery shops are unlikely to have this equipment. The most practical way to achieve a bend is to cut grooves in the concealed surface (which might be the inside or the outside of the bend), thus making the plywood more flexible. To restore the strength of the bend it's common to glue a moulded block of wood or a reinforcing strip of thin plywood onto the grooved section. We have a CSIRO brochure on Plywood Bending which we could fax or email to you if you need further information.

Q. What moisture content should timber be at before installation of plasterboard? In this case it is a house in Bundaberg awaiting flood rectification. AS2589 says 18% for NZ and the superseded 1997 version named Category A timber as less than 16%.

It is a little confusing in that at least one manufacturer (BGC Plasterboard in Perth) calls for timber to have a moisture content "less than 16%" at time of lining (BGC Installation Guide Oct 2010). The Queensland Building Services Authority's "Plasterboard & Painting Guide" of June 2008 includes the same requirement. However, AS/NZS 2589-2007 clearly states the following: “The maximum moisture content for timber framing at time of installing gypsum linings shall be 18%” (para 2.6.3). In practical terms there is very little difference in the way timber at 18% will perform, compared with timber at 16%, so it's a bit academic. Resistance moisture meters are only accurate to ±1.5% at best.

Q. I am looking to build a few different kinds of boards using reclaimed teak wood that I have sourced in Bali. I was wondering, is it possible to create a skateboard that can flex using teak wood? How would it affect the strength? Would I have to mold and laminate different layers or could it be shaped from 1 piece? I also have created a few hand surfboards using the same reclaimed teak wood. I am using 6-7 coats of teak oil now as a finish. Is there a better natural/eco-friendly coating that you would suggest to further protect the teak from the sea water and sun? Thank you for your very informative site and your help with the questions above.

Skateboards are usually made from a number of veneers, like plywood. Glue is applied to the veneers which are flexible enough to be pressed into the required shape, ie. turned-up nose and tail and a slightly concave centre. When the glue sets, the deck holds its shape. It would be impossible to form a solid piece of teak in the same way. It's a practical option if the teak is sliced into veneers, and if you have a press that will create the right shape, but otherwise we don't think it will work. Regarding a finish for the surfboards, we feel that a natural oil finish might not last in the fairly aggressive environment of sand and surf, nor would it seal the wood very well. In our opinion you would be better off with a durable varnish coating, eg. a product formulated for wood floors.

Q. I have tried injecting pyrethrum insecticide without any success. Would painting the palings help control the borers?

Pyrethrum is a natural insecticide, so it should work. However, bear in mind that injecting it into existing holes might not reach all the larvae already in the wood, since the holes are exit holes created when the mature insects bore their way out. The purpose of injecting insecticide into the holes is to try to penetrate adjacent wood, as well as protecting against re-infestation via the existing holes. So some exit holes may continue to appear after treatment. However, it wouldn't hurt to try a different insecticide if you feel you're not making any progress. Regarding painting the timber, it might help although there will be some spots you can't get to, eg. the interface between the palings and the fence rails. Also remember that if it is the Lyctus borer, as we suspect, it's only able to attack sapwood which will comprise a relatively small proportion of your timber.

Q. I am a carpentry teacher and will be teaching Construct Wall Framing next week. For stick framing, do you have a formula for estimating the lineal metres of pine stud/m required for general wall frames that would include openings? Thanks for your help as this will help in teaching estimating of materials from a plan.

It's difficult to come up with a single formula that will apply to all wall frames since the sizes of door and window openings vary greatly. However, there is some helpful information on the net at this website - http://toolboxes.flexiblelearning.net.au/demosites/series10/10_01/content/bcgbc4007a/04_organise_materials/06_timber_calc/page_001.htm.

WoodSolutions

Did you know?

In 2008 seventy percent of known old-growth are in nature conservation reserves.