Ask an Expert

Ask an Expert

Joinery, cabinetwork & furniture

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 work for an office screen manufacturer at the moment we have just got our FSC badge but we have had to change ply makes from Malaysian to Chinese, we are seeing a big difference with boards warping we bond our ply to the mdf using PVA Glue is this happening due to the change of ply or is this a manufacturing error if so could you advise on the correct situation.

PVA glue is water-based and we believe the water content of the glue is most likely causing the problem. There is a useful discussion on the net about this which you can find via this link: Using a backer sheet and/or a high solids PVA should overcome the problem.

Q. Brilliant! I think that might be the cause. Now I wonder how to get rid of the stain...

Your previous message said that bleach had failed to remove the stain, so it's unlikely to be mould and much more likely to be a case of "iron stain" as explained in the Timber Veneer Association's data sheet. If so, oxalic acid (or a brand-name timber cleaner containing oxalic acid) will remove the stain. To find out more about iron staining write "iron stain on wood" in your browser. Several references will come up, but the data sheet issued by the US Forest Products Laboratory is particularly helpful. Note that for oxalic acid to work it needs to be applied to bare wood, so any coating will need to be sanded off first.

Q. Have you ever seen or heard of this dark staining before? I have attached an image of our Tasmanian oak cupboards FYI. I have done a lot of research and asked various tradespeople.

We wondered if you are located in a humid climate, eg. the northern part of Australia. Problems have been experienced with eucalypt veneers (eg. Tasmanian oak) in damp and/or humid environments. The Timber Veneer Association of Australia (TVAA) recently published a data sheet on the subject which can be downloaded via this link: Although aimed more at building contractors and specifiers it might help to identify a possible cause of your problem.

Q. We have a 16 year old Tasmanian Oak kitchen. The doors have an " insert" which is turning very dark from the edges inwards. This stain doesn't respond to washing, bleaching or vinegar. Would like to send you an image but can't on this webpage submission form. Wondering if you can assist at all?

Presumably the dark stain is not mould or it would be removed by bleach. Perhaps moisture has penetrated under the surface coating so the bleach is not actually making contact with the mould. In that case it might be necessary to re-finish the doors, ie. remove them, sand the insert panels back to a clean surface, and re-seal with polyurethane. If you are sanding the panels remember to sand with the grain, not across the grain.

Q. A recently-widowed neighbour has asked me to help value a stock of craft/furniture-grade timber her late husband has left in his shed. She wants to try to dispose of it sensibly, without trying to "get rich quick". I'm hoping to find a price list of a range of typical timbers to help set realistic prices to interested potential buyers locally. As a retired woodwork teacher I have some experience in the field but am out of touch with values. Can you help?

I'm afraid we don't monitor prices and in any case they vary between suppliers. Your best bet is to contact a specialty timber supplier and ask the cost of the species concerned. If you write "Australian specialty timber suppliers" in your browser several names will come up. That should give you a rough idea of the value of the timber and one of them might turn out to be a buyer.

Q. I have found dry rot in some new furniture I bought recently. However, I am looking for an independent expert who can examine the problem and give me a report to confirm whether I am correct. Can you point me in the right direction?

There are several people around Australia with the expertise you need. If you are located in NSW, State Forests no longer provide an inspection service, so please ignore previous answers posted on our website that refer to State Forests. However, their former inspectors have formed a private company and you can access their details via this link: In Victoria, Dr. John Thornton (formerly of CSIRO) provides a consulting service, phone 0407 050 468. In SA there is a company called Timber Consulting Pty. Ltd. which could provide a report for you, phone (08) 8373 5285. Having said that, dry rot in furniture would be unusual. The term "dry rot" is a bit of a misnomer since all decay-causing fungi need moisture. On the other hand it's possible the furniture was made from wood that was milled from a log that had a pocket of rot in the standing tree.

Q. Want some direction in who I can talk to to get some technical info/ direction on the acceptable variances in veneer colour. We have an architect that is expecting every veneer sheet to match exactly. Thanks in advance.

We don't provide a telephone advisory service, but the Timber Veneer Association of Australia (TVAA) has an info line on 1300 303 982 which may be able to help. Generally speaking, veneers are subject to the same colour variation as timber. Veneers from different logs, or from different parts of the same log are likely to vary in colour and grain pattern. This can be limited to some extent by selection.

Q. My builder is intending to re-use MDF as a door frame in my renovation. I am not happy about this and need some advice. I am concerned as it is cracked, it has nail holes and has expanded at the base. Do you have any regulations that govern when and when not to re-use MDF for internal door frames?

It seems the door frames have been removed during the renovation and now the builder wants to re-install them. If the MDF has expanded at the base it sounds as if it was wet at some stage. There are no specific regulations covering this issue, although there is a general presumption that materials shall be "fit for purpose". It's surprising how much damage can be concealed by filling and painting, but it's really a matter for discussion between you and your builder. If you feel the MDF is beyond repair, then it would be better to have new material. Of course your contract with the builder will also have a bearing on the matter. If it was agreed at the start that the door frames would be re-used, rather than replaced, the builder may now want extra payment to supply new ones.

Q. I have a coffee table and the heater has melted the veneer on 2 legs. I am after a product that we can use to replace the veneer either an iron on or glue on product. Is there such a product?

We can confirm that iron-on veneer is produced by Consolidated Veneers and their phone number is (02) 9604 8100. Some of their products are available through hardware stores, but it’s best if you phone them and explain exactly what you need.

Q. We had a solid blackbutt front door installed, gets morning sun (Adelaide). Door has vertical inset glass panel on one side. Two doors have failed in that they have shrunk considerably and warped a little. Manufacturer maintains the timber is suitable and have used it for external window frames but we're opting for the replacement in WRC. Any thought on blackbutt for this use?

It sounds as if it's not so much a question of unsuitable timber as unsuitable moisture content. We consider blackbutt a suitable timber for external doors and windows but like any timber it will shrink if installed with a moisture content that is too high for its intended location. Adelaide is relatively dry, although at this time of year it can be cold and wet so properly dried timber shouldn't be shrinking. We wondered if the manufacturer carried out any moisture tests on the timber before making the doors - that's always good practice to avoid problems. However, if you have decided to replace the doors in western red cedar that is a timber that is more forgiving. Cedar is a very stable timber with little tendency to shrink and swell, even when fully exposed to the weather. The only disadvantage is that cedar is quite soft, but it should perform satsfactorily with normal care.


Did you know?

Logs from plantations cannot produce the sawn hardwood timber produced from logs currently harvested from native forests.