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'm trying to find a table showing the standard sizes of Blackbutt. We are looking at using Blackbutt for timber decking and for some bench seats. If you can send me in the right direction to where I can find some timber size tables for Blackbutt, it would be much appreciated.

You will find standard sizes for blackbutt decking on the Boral website if you paste this link into your browser: http://www.boral.com.au/productcatalogue/product.aspx?product=64. Other suppliers may have similar information on the net. If you are comparing sizes and prices, bear in mind that you need to be comparing "apples with apples". The sizes quoted by Boral are kiln-dried dressed sizes, so they will differ from sizes quoted on an off-saw basis. For example an off-saw piece of timber 25mm thick will finish at 19mm after planing and kiln drying.

Q. I am starting to make windsor chairs and need a suitable local timber to steam bend the continuous arm. Spotted gum has been mentioned. Any other species? Have local timber mill at Millfield NSW

Hi Rex

Thank you for your question.

It is difficult to confidently nominate timber species suitable for steam bending as it is a bit of an art and success is mainly based on hands-on experience and trial and error. As you point out, spotted gum is considered a good species for steam bending.  Other species also considered good for steam bending include: alpine ash, mountain ash, blackwood, messmate, karri, Huon pine and radiata pine.  In relation to suitable local species, you may have to do some experimenting, both with species and steaming times. Straight grain, knot free pieces of timber are a good start and to save time, we'd suggest trialling square sections first.

Q. We have recently completed a project that has a bench joinery unit in the foyer. It is lined in a Tasmanian Oak timber veneer with a clear finish. I have attached some images where we are concerned about the difference in colour between the panels. We have asked the joiners to replace but they are saying that they cannot guarantee the colour between panels. Is there some guidance or regulations on this and do you think that what they are saying is acceptable. Your advice would be appreciated.

The relevant Australian Standard is AS/NZS 1859.3:2005, "Reconstituted wood-based panels - Specifications, Part 3: Decorative overlaid wood panels". However, the Standard deals with manufacturing issues rather than subjective matters such as colour variation. It is true of course that wood products from different sources (different logs, different forests) vary in colour, even within the same species. But if your images are accurate it seems the joiner has made little or no attempt at colour matching. Colour matching is not a particularly scientific process, it's just a matter of selecting veneers of similar colour and grain for components that are going to be abutting one another in the finished job. Depending on what your specification says, and what discussions were held prior to manufacture (if any), we feel you may have a case for replacement of those panels that show the greatest mis-match.

Q. I am designing a bar for a night club in Sydney and I am researching timbers. My client would prefer to use timber for the bar. I have not worked with this material for a bar before, could you please suggest to me what the best timber would be to use in this case?

A timber bar is exposed to hard wear in a nightclub environment so we suggest a hardwood. You will find a range of possible designs, including curved tops, on the Dale-Glass website at http://www.dgi.com.au/curved_benchtops.html. Suitable hardwoods include jarrah and brush box, depending on colour requirements. As well as choosing a dense hardwood it's important to choose a finish that will stand up to wear and tear and resist liquid spills. We would normally recommend a two-pack floor varnish, but the manufacturer may have other suggestions. Correct installation of benchtops is also important, and again you will useful guidelines on the Dale-Galss website at http://www.dgi.com.au/bench2.html.

Q. I am wanting to make three box shape coffee tables for my home. Being three different sizes, I am wanting them to sit within each other for the ease of storage. I am wondering if Oregon would be the best timber to use, keeping in mind that they can’t be too heavy for the grandparents to lift.

There's a trade-off between light weight and wear resistance, so the lighter the wood the softer it will be and hence less resistant to denting. Also oregon might not be available in a suitable quality. Since the tables are designed to fit inside one another we would be inclined to go for one of the lighter hardwoods which will stand up to wear and tear better, but still be reasonably easy to lift. For example, Victorian ash is readily available in a quality suitable for joinery and is tougher than a softwood.

Q. I am creating art for our front fence, eg. Santa Claus and his Reindeers. I want to use timber approx. 4mm thick. I will draw Santa on timber, cut it out with jigsaw and then paint it. How do I protect it from the weather, eg. sun & rain and what sort of timber should I use?

If you are thinking of plain timber we would suggest western red cedar for your artwork. It's readily available, easy to work and has good weathering properties. Ordinary house paint will provide sufficient protection if applied to all surfaces (front, back and edges). However, if you need large sheets to cut out the figures perhaps preservative treated plywood would be a better choice. Treated plywood is marketed under the name Shadowclad for wall cladding. It's grooved on one side but smooth on the other, so you could use the smooth side. Have a look at the product in a timber merchant's yard to make sure it will be satisfactory. Another possibility is tempered hardboard, but it might need a frame to give it stiffness, depending on how large the figures will be.

Q. I have just had a new blackbutt staircase installed. The stair people's standard form says that the stairs have to be sealed top and bottom to reduce shrinkage. I was planning to use Bona for the upper surface but wonder whether blackbutt really requires sealing underneath as well. The previous stairs (silver ash) were in place for over 20 years without shrinkage and I don't think they were sealed underneath. On the other hand, I don't want to take any risks.

The stair makers are taking a precautionary approach, since they don't always know the conditions to which their stairs will be exposed. Where kiln-dried timber is used in a stable indoor environment, it shouldn't be necessary to seal the underside. However, if the stairs are exposed to sun shining through windows, or some other effect that could cause unusual drying of the wood, then sealing it all round could help to minimise problems.

Q. Thank you very much for your response. I am still at a loss as to why the bench has moved so much. It is a square (1400 x 1400) island top, so is fixed at four points. The end that has warped up, see pictures attached, is the 'work' side. The other end has a 300mm overhang (the breakfast bar aspect). That end is bent downward, but not to the extent that the work end has bent upward. Attached are some photos of the warped end. Do you have any more comments on why it occurred?

The images of your benchtop were a help, although it might need an inspection to really pin down the cause of the problem. However, we feel the most likely factor is incorrect installation. In our previous answer we referred you to some of the installation guides available on the net, particularly the one published by Dale-Glass Industries. Note the comment that timber benchtops must never be fixed in all four corners unless there is an allowance for movement, eg. with screws in oversize holes. From your photos it seems the timber has tried to shrink and, being unable to move in a sliding action, has pulled the sub-frame upwards. If the connection to the sub-frame had been stronger, perhaps the top would have stayed flat, but split instead. If it's possible to view the underside of the bench you might be able to see whether the recommended procedure has been followed, ie. whether the screws are in oversized or slotted holes (correct), or whether the bench is tightly held at all four corners (incorrect). It's also possible that the underside of the benchtop was not sealed and consequently absorbed moisture, while the top (being sealed) did not. This would contribute to the problem.

Q. I had a spotted gum island benchtop (1400 x 1400) installed in my new kitchen 18 months ago. About 7 months ago I noticed that one end was bending up and the other end was bending down, but to a much lesser extent. The end that bent up ripped the battens it was fixed to underneath, up and fractured them, it is quite a curve upward. The cabinet maker who installed the benchtop but didn't make it said the problem was to do with how the timbers were laid. He said the grain should alternate with each timber plank, so looking at the end cuts, the direction of the grain should be over (n) and the next should be under (u) etc, so any tendency to bend is counterbalanced.. When the benchtop maker looked at the bench he said it was a common problem with spotted gum, and occurred in 60% of benches because the wood is so hard / dense and it doesn't dry evenly. The timber used is kiln dried. He said the only way to fix the problem is to cut all glued joins, re glue it and re polish, although still a 5 % chance it can occur again. Is warping a common problem in spotted gum benchtops? Should the timbers be laid / joined in a certain fashion to avoid warping? Thanks for your help.

It's hard to give you a definite answer without seeing the benchtop. The cabinetmaker is right from a theoretical point of view, but if the timber was properly kiln dried its movement in service should be fairly minimal and the direction of the grain is then only a minor factor. We wondered if the benchtop had been installed correctly. Although movement in service is relatively small, timber benchtops can still move slightly, particularly if they are near a heat source such as an oven or cooktop. The installation method must allow this movement to take place withour pulling the sub-frame apart. There are various installation guides available on the net, and one of the best is published by Dale-Glass Industries. You can download it via this link - http://www.dgi.com.au/bench2.html. We suggest you have a look under the bench to see whether the recommended procedure has been followed.

Q. Please help. I am looking for information about PLY types available that would most suit childrens toys and mobility bases. Approximate thickness from 16mm to 12mm would be suitable. What type of PLY and grade is available that would leave a chamfered edge (approx 2-4mm) and be least likely to chip and or splinter? I have seen 16-18mm PLY used for high chairs and mobility bases for disabled children. The PLY seems to have more laminations per thickness than the standard AS/NZS Hoop and radiata pine. The products I have seen are imported from America. I need to stay local. Also do you have information about the best coating to use in order to stop it chipping around the edges. I was hoping to use a child friendly oil. But am realising it may have to be varnish or something similar. I work as an Industrial designer for the Centre for Cerebral palsy.

It sounds as if you will need plywood with an A-grade face both sides. We suggest Marine Grade plywood, not because of its boatbuilding qualities but because it is manufactured with an A-grade face front and back and is sanded both sides. Other grades of plywood, such as Interior Grade, are generally only made with one A-grade face on the assumption that the back will not be seen. Hoop pine is less likely to chip than radiata pine as it is an even textured wood, generally with a straight grain. Regarding a finish, we strongly advise against an oil as oils have little resistance to moisture and become grubby with regular handling. A varnished surface can be wiped clean with a wet rag. If the items are likely to have particularly hard wear we would recommend a floor varnish. Otherwise a normal satin grade polyurethane will give good service.

WoodSolutions

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.