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Interior timber & flooring

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 have been living in a house the past 2.5 years with grey ironbark "oiled" wood floors. In essence, the floor was very sensitive in general. We have had some minor scratching, where the children's single beds were. They were white painted wood beds. As well, there was one corner where the felt protection pads would occasionally come off a wing tip chair, and the metal underneath and have several scratches from this. Nothing is deep. Most are normal wear and tear, from the friction of children getting in and out of bed, or the bed having been moved a few centimeters during the years. What I am trying to ascertain is: a.) is it possible to just repair the areas where the scratching has occurred. Through spot sanding, or sanding the floorboards in the room the beds were? b.) Would re-oiling or treating the floor (the owner wants to use "Synteko classic" to treat it now) suffice to not "see" the scratching. The owner has told us he needs to re-sand his entire house. We are trying to understand whether this be necessary, as we do not believe the scratching is to that extent (not through entire house, not in hallways, or stairs etc.) I would greatly appreciate your feedack as quickly as possible as this is an urgent matter.

It's difficult to give you a definite answer without seeing the floors. As a general comment we can say that ironbark is one of the harder flooring timbers and we wouldn't expect wooden beds to do much damage. Wingtip chairs usually have a wooden frame, and wood-on-wood should only produce scuffing rather than deep scratches. We suggest trying to rub in some oil with a very fine-grit wet and dry sandpaper to see if that fixes the problem. Re-sanding the whole house seems a bit excessive, but if the scratches need to be sanded out with a floor sanding machine it's not possible to sand a small area. Once you start you have to keep going, otherwise you get a patchy effect.

Q. I am going to lay a 21mm reclaimed T&G mixed ash floor over a 19mm yellow tongue particle floor. This sits on top of an old (80's) poured concrete slab. I've laid a poly/plastic moisture barrier between the slab and the sub floor. As I will be using 108mm boards I've been advised to glue the board as well as top nail. Is this the right way to go and if it is, what size nail is best (I'd prefer to top nail over secret nail/staple but happy to be advised otherwise. I was thinking a 35 mm nail with glue but is longer better (and what about the barrier and method - planning on the old claw hammer and not pneumatic).

The recommended nail for top nailing is actually a 50 x 2.8mm bullet head. However, you only have 21 + 19mm of depth (slightly less when the nails are punched), so a 35mm nail with glue is the best way to go. Also the assistance of glue is advisable when nailing into particleboard since the nail-holding properties of particleboard are less relaible than timber. Run a bead of polyurethane flooring adhesive at 90° to the floorboards, midway between the the location of the nails. Polyurethane adhesives have some elasticity which allows the flooring to move slightly in response to changes in humidity.

Q. How to replace board without dismantling all floor?

The usual technique is to rip the damaged board down the middle so the two halves can be pulled out, or simply cut the tongue off so the board can be prised up with a chisel. Then a new tongued and grooved board can be folded in if the bottom of the groove is removed. It's easier to explain with a diagram and there is a very informative data sheet available on the net via this link: Refer to illustration 4 on page 4.

Q. What type of timber do you recommend for timber floors. ie: does bamboo flooring have a higher impact/scratch resistance than say a dark hardwood timber?

Bamboo flooring varies in hardness and scratch resistance depending on how it's made. There is a lot of negative comment on the net, but the better products (strandwoven and hot pressed) are quite hard. Scratch resistance depends on the coating - the better products have a number of factory-applied sealer coats. Bamboo is actually not a wood product, it's a grass, and the flooring is made by gluing strips of bamboo together under pressure. The major weakness of bamboo (assuming one of the harder types is selected, with a durable coating) is the conflicting reports about sanding and re-finishing it after a period of wear. This is not something we've tried ourselves but reports on the net suggest that (a) formaldehyde is released from the glue, no doubt as a result of heat generated in the sanding process, and (b) the surface is inclined to tear rather than sand smoothly. Having said all that, the need for high impact and scratch resistance depends on the situation. Baltic pine was a very popular flooring material in the past, although it is quite soft. But with rugs in high traffic areas, and under normal domestic wear, Baltic pine performed well and created an attractive floor. However, if impact resistance is important in your situation, a hardwood such as ironbark will wear well and can be sanded and re-finished a number of times.

Q. We want to lay a top quality hardwood timber flooring to a heavily used hallway between the kitchen/family room and lounge/dining rooms. We were thinking of Jarrah but found out it does not rate very highly on the Janka scale and it appears to be a bit dark? What light red Australian timber do you recommend that is extremely durable? We were thinking about Redgum or Red Ironbark. We would like the floor to have the widest sized panels allowed with secret nailing. What do you recommend?

Red ironbark is exceptionally hard (Janka value = 14) but it's a similar colour to jarrah. River red gum is generally a bit lighter, although it too can be a similar colour to jarrah. Brush box might suit your colour range better. It has a Janka hardness rating of 9.5, compared to jarrah at 8.5. These Janka ratings are generally OK for normal wear as long as a suitable finish is applied. It's only if the floor is subjected to stiletto heels that denting may occur. Regarding width of boards, the Australian Standard recommends a maximum width of 85mm for secret nailing.

Q. We are a Sydney based architects studio. We have projected a skylight supported by timber members. Our engineer recommends F11 grade timber. We want to match them with the rest of specified WRC. The builder suggested a merbau timber for that purpouse. Can we achieve F11 graded merbau? If not, can you please recommend another F11 timber to match WRC colour?

Kiln-dried merbau would be at least F14 grade and generally significantly higher unless it was unusually poor quality material, so there should be no difficulty meeting the F11 requirement. However, we suggest you ask the builder to provide a sample so you can be satisfied about the colour. Merbau is a reddish brown colour, whereas western red cedar is a light-brown straw colour. Rather than trying to match the cedar, perhaps a contrast would be acceptable, in which case we feel merbau would give an interesting colour accent.

Q. Trying to find technical and best trade practice advice for the laying of parquetry flooring for an alterations and additions project in Sydney, over existing (70 year old) timber floor structure to part of the project and new timber floor structure to other areas. Some rooms are to have strip flooring, some to have parquet. How do we best allow for the differing thicknesses of the products at door thresholds where the flooring changes. Do we lay both the strip flooring and the parquet over particle board. Are there any resources you can direct me to?

There's some good information on the Wood Solutions website, including a design guide on the installation of strip flooring. To download the guide, visit the Wood Solutions website via this link: A section on the installation of parquetry is included in the Boral timber flooring guide, available at With regard to adjusting different thicknesses of flooring, perhaps this could be done by using underlays of diffferent thickness to bring the flooring up to a common level.

Q. We were going to specify Tallow wood timber floor boards (175mm x 21mm) in a residential project at Airlie Beach. One supplier did not want to quote on the project due to the high humidity in the area. We had assumed that if the boards were properly acclimatised that there would not be an issue with the boards cupping. But are now concerned that the species or the width of the boards may be an issue in this location. Would you please be able to provide some advice as to whether this specification would be ok if the boards are properly acclimatised on site or if the width of the boards will always be an issue in this climate and a smaller width should be used? Any information would be greatly appreciated.

Airlie Beach has a tropical climate and therefore higher humidity than southern parts of Australia, particularly during the wet season of January to March. The relative humidity can be up to 80% with a daytime temperature of 30°C. If these conditions were sustained, timber would have an equilibrium moisture content of around 18%. On the other hand, if the house is air conditioned, temperature and relative humidity will be lower. The worst situation for timber would be if the residence is only occupied intermittently, with air conditioning, and then unoccupied with the air conditioning turned off. The humidity in a tropical climate is relatively even, but intermittent use of air conditioning would result in greater swings in wood moisture content than would occur in an un-airconditioned environment, or in a permanently airconditioned environment. Cupping of floorboards is not necessarily an issue, but swelling and shrinking in width may be. So the answer depends on how stable the humidity will be in the indoor environment. If humidity is likely to vary greatly, using narrower boards and appropriately located expansion gaps would be advisable. You will find more detailed information about the installation of timber flooring on the Wood Solutions website at this location: Design Guide no. 9 deals with flooring and can be downloaded free of charge.

Q. My house is clad on the outside. I have laid a ply floor over the concrete I was wondering would there be any adverse effect if I was to lay the timber strip flooring before the plaster board went in as I have had the flooring on site for some time now and I was wanting to get it down before anything starts to happen to it. The timber is Aussie mixed and I was going to cover it with a floor protector after the flooring had been laid.

We trust there is a moisture barrier under the plywood, as recommended to prevent moisture migrating from the concrete into the timber. If the house is enclosed there seems no reason to delay installing the flooring, if you particularly want to get it down - as long as it can be protected from future trades (plasterboard installers, painters, etc). We assume the flooring has been stored in a dry spot where it has not picked up any moisture, and therefore doesn't need any additional "acclimatisation". To protect the flooring, sheets of loose laid particleboard or plywood might be best - plastic is likely to tear.

Q. I have three packs of 500 lm strapped mixed hardwood flooring. Due to the crane we were unable to get it all the way under cover. Should I remove the straps and move the packs undercover and out of the sun or should I just leave them where they are? I'm concerned about the condition of the timber due to rain and moisture and sweating in the plastic. Any advice would be helpful.

We strongly recommend you move your flooring to a stable environment, preferably indoors where there will be little or no fluctuation in moisture content. This also gives the flooring a chance to "acclimatise". When timber is kiln dried, the stack reaches a target average moisture content, but that doesn't necessarily mean every board ends up with the same moisture content. If you store the flooring indoors for a while before installing it there will be a chance for the timber to adjust to its environment, and for any moisture differences between boards to even out. "Sweating" (ie. condensation) inside the plastic is highly undesirable since in extreme cases it can leave stains on the wood.


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%.