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. We have just had some renovations completed. The timber window frames have had the sill drips either covered by the weather board or no drip was cut into the window sill. I brought this to the attention of the builder and he assured me that as the windows have had silicone around the exterior frame work that would suffice regarding water penetration and deterioration. Is this an acceptable method of installation?

The purpose of the drip groove is not only to form a capillary break that stops water running back along the underside of the sill, but also to make it drip off beyond the wall, rather than wetting the wall immediately under the sill where the wall will stay damp. Silicone may stop water running back into the house (although we are not in favour of relying on silicone in the long term) but it won't stop water from wetting the area under the sill. A UK website (admittedly a wetter climate) talks about bridged drip grooves in the following terms which we endorse:

The underside of window sills should have a shallow groove running along the full length. This drip groove stops water running back along the underside of the sill and soaking the wall. If the drip groove is bridged with layers of paint, moss or debris, rainwater will quickly soak the wall beneath the window.
Symptoms – Outside: mould or mildew growing directly beneath the window sill. Inside: Damp patches or mould directly below the window. Rotten timber sills.
Solution – Scrape out the drip groove and then repaint the sill if it is still sound. Alternatively, nail a thin wooden batten along the full length of the underside of the sill. This will deflect water running back along the sill.

We also make the point that windows should have flashings installed to prevent water entry, rather than just silicone, but perhaps your builder has installed flashings as well as silicone.

Q. I am a heritage consultant looking to find an appropriate timber that could be used as a veneer on a replica solid core door to match a 1920s solid polished rock maple door. I have a photograph that may help.

Rock maple veneer is still available in the marketplace, but different batches vary slightly in colour and grain. You might want to see some samples to ensure you get a reasonable match. Alternatively you could send your photo to a supplier to see if their rock maple looks similar. We understand that Briggs Veneers stock rock maple. For details click on this link or copy it into your browser:

Q. Can I just ask a quick question: what is the best solid timber suitable for bathroom vanity?

We consider that design factors are just as important as the type of timber. For example, it's not recommended to sit a timber vanity directly on the floor if there is any likelihood of contact with water round the base of the vanity. It should be raised off the floor on a brick or concrete upstand. Setting a handbasin into a timber vanity top can also be challenging unless the timber is carefully sealed on all surfaces, including the edges of the cutout, before the basin is installed. Even then it's best if water doesn't pool up on the vanity top, either behind the basin or adjacent to the edges. Bearing these points in mind, a number of timbers are suitable, the critical factor being that the timber must be kiln-dried, with tops installed so slight movement can take place. For more detailed advice on the installation of timber benchtops, refer to manufacturers' details. A good example is the guide published by DGI Industries which you can download via this link On that website you will also find details of available timbers.

Q. Can you please call me re formaldahyde free chipboard?

Telephone advice is not available through this service but we can say that the Australian Standard covering manufacture of particleboard provides for three levels of formaldehyde emission, E0, E1 and E2. Australian manufacturers have generally adopted E0 and E1 for their products. Despite the name, E0 doesn't imply zero formaldehyde content, it just means it's very low. The E0 specification limits emissions at the time of dispatch to 0.5 mg of formaldehyde per litre of air, while the E1 limit is 1.5 mg/L. These are upper limits, so a particular sheet of particleboard may have a lower formaldehyde content, depending on how much time has elapsed since manufacture.

Q. I need advice regarding matching veneer. I am dealing with an architect whose requirement for a veneer applied to a flush door panel has the same grain pattern in all aspect in all panels. We have more than 500 flush door panel project. My common practice is just apply a veneer from the same bundle in one panel for a perfect match. Of course, when need arises, I will get from another bundle that is matching to complete a panel. What is not acceptable to the architect I am dealing with is that, all the flush door has different grain pattern since I used a crown cut. To better understand the situation, he is expecting that the grain pattern is the same as the wood grain laminates, uniform in every panel. My question is, is it really a common practice in commercial door manufacturing that every panel is the same in that aspect with the use of natural veneer.

It's not possible to produce 500 flush panel doors with exactly the same grain pattern from natural wood veneer. It is possible to achieve a similar result by using veneers from the same bundle, as you say, but natural veneers vary according to the growth pattern of the tree from which they are cut, and according to their position in the tree. They will never be as uniform as artificial wood grain laminate. However, it is possible to achieve a consistently repeated grain pattern from reconstructed veneers. These are made by peeling veneers, colouring them, laminating them into a block and then slicing the block to produce the desired grain pattern. Reconstructed veneers are made from natural wood but there is less variation in colour and grain because of the manufacturing process. Perhaps reconstructed veneers would be more suitable for the job in question. You may wish to refer the architect to the website of the Timber Veneer Association of Australia (TVAA) at this address:

Q. When specifying to replace timber window sashes, would a softwood or a hardwood be better - we have been advised both ways!

In our opinion it's the properties of the timber that are more important than simply the question of whether it's a hardwood or a softwood. For window sashes, dimensional stability and rot resistance are perhaps the most critical, although if a natural wood look is required then the colour of the wood may be important. And in bushfire areas only certain species of timber may be permitted, depending on the severity of the bushfire rating. Assuming we are only concerned with the stability of the wood and its rot resistance, western red cedar performs well although quite soft. If it's a commercial building where the timber might get knocks and scratches then a durable kiln-dried hardwood might be preferable, such as jarrah, merbau, etc.

Q. I am hoping to purchase an old already sanded untreated hoop pine table. I think I would like to keep it untreated (do you call these tables scrub top tables? Years ago in UK old pine or oak table tops untreated were called 'deal top' tables. Is that the same as 'scrub top' do you know?) If I have to treat it would I be best to use a wax or something like tung oil?

"Deal" is another name for two of the softwoods commonly used in the UK, eg. spruce or whitewood is also known as white deal, and Scots pine or redwood is also known as red deal, particularly when imported into Britain from the Continent. So tabletops made from these timbers are known as deal-top tables. (It's somewhat erroneous if the top is actually oak!) The term "scrub top" strictly applies to an old table that has been sanded or otherwise cleaned up and presented for sale with a "scrubbed" top. However, marketing terms acquire a life of their own and it's quite possible that brand new tables are also sold as "scrub top tables" simply meaning the tabletop is bare wood. A table with a bare timber top will mark easily. Anything spilled will soak into the wood leaving stains and watermarks, so we would strongly recommend you seal it. Oil or wax won't form much of a barrier against liquid spillage, and hot mugs of tea or coffee are likely to leave white rings on the table. Our preference is for a polyurethane coating which provides a protective surface and one that can be wiped clean. Polyurethane is available in matt or satin grades which give a natural finish to the wood.

Q. I have constructed a table using a slab cut from a Deodar log, with very pleasing results. I have finished it with Organoil. The timber is (apparently) notorious for oozing pitch, mainly coming from knotty areas, of course. I have tried to draw the pitch out using a heat gun (which is easily done) but it seems to be neverending, especially when exposed to the sun. Is there any way to fix these areas in-situ? The only solutions I have seen discussed involve kiln drying, which is too late, I guess.

There are various suggestions on the net, which you will find if you write "stop resin bleed" in your browser, but they all involve a sealer coat followed by a paint finish. Unfortunately we don't know of any remedy that would allow you to retain a natural finish such as Organoil. All we can suggest is to try to shade the table from the sun and/or continue to draw the resin out with a heat gun. It is correct that kiln drying hardens resin - in fact you could heat the slab in your oven except it probably wouldn't fit. But if the resin isn't set, or crystallised, by exposure to a relatively high temperature it is likely to continue to bleed for a long time.

Q. We are working on an interior refurbishment and require some internal vertical slats to divide some areas of the space up. Who can we contact to help with this?

Your best contact would be a joinery works in the Sydney area. Various names will come up if you write "Sydney joinery" in your browser, eg. Top Knot Joinery, etc.

Q. I have an enquiry regarding a spotted gum timber veneer we have specified on a project in Melbourne. The project has been completed for some 6 months now and have specified a spotted gum veneer to all external doors. The veneer has been applied to both the outside and inside face. The doors that are facing west getting direct sunlight have had the veneer crack substantially on the outside face. The veneer has had several coats of polyurethane applied to seal the door and to maintain the rich colour. Can you please advise why this may have happened. Is it that the supplied veneer installed was very green (moist) which has not been dried out enough prior to installing? I would appreciate your expert advice/assistance on this.

It's unlikely that the veneer was green since veneers are quite thin and hold little moisture. Nevertheless, they do have some moisture content and it seems that exposure of the doors to the western sun has caused enough shrinkage to create cracks in the surface. We assume that the same veneer on the inner face of the doors has not cracked, which would indicate that the veneer itself is not faulty but simply unable to tolerate direct sun. No doubt the veneer is attached to MDF or particleboard, which will have a different shrinkage rate to the veneer, and this is likely to exacerbate the problem. We don't have any simple remedy for this problem, other than to replace the outer face of the doors with a material better able to resist direct sun.


Did you know?

About 6% of Australia’s 147 million hectares of native forests are public forests potentially available for timber harvesting. Timber is harvested from about 1% of those public native forests each year.