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Referring to Australian National Timber Dev. Council's web site, we noted that merbau is defined by AS-3959-2009 as bushfire-resisting timber. Could you please advise us is it classified as non-combustible material? Equivalent to BS 476?

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Merbau is classified as a bushfire-resisting timber in Australia because it has fire characteristics similar to timber treated with a fire retardant. This doesn't mean it won't burn, just that the heat released when it does burn is within the limits specified in Australian Standard 3959-2009.

British Standard 476 has a number of parts. The part dealing with non-combustibility is Part 4 which specifies a test to differentiate between non-flammable materials, such as plaster-based wall linings, and materials which undergo flaming combustion, such as wood products. It is most unlikely that any wood product would achieve classification as a non-combustible material as defined in BS 476: Part 4. Of course, "non-combustible" materials may still have undesirable fire qualities in that they may melt, shrink, collapse or change their nature in some other way. However, by definition they will not contribute to the fire load.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide – Building with timber in bushfire-prone areas.

AS-3959-2009, British Standard 476, BS 476, merbau, bushfire-resisting, bushfire, BAL

Can you advise as to whether unpainted, untreated hoop pine exposed in a marine environment (i.e. regularly doused with salt water) would exhibit rot resistant qualities?

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Hoop pine is not a durable timber, and we would not recommend it in exposed situations, marine or otherwise. It's a fine timber for protected uses but has little resistance to wood rot when untreated.

For more information about the design with respect to durability, download the free WoodSolutions guide – Timber service life design – design guide for durability.

hoop pine, marine, durability, salt water

Hello, I am considering using WA Karri as a solid timber floor. I have heard conflicting reports that Karri "moves" a lot more that other similar timbers (eg Sydney blue gum, Jarrah).

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When we talk about timber products "moving" we are referring to the swelling (or shrinkage) that takes place with a change in moisture content. If there is little or no change in moisture content, there is little or no shrinkage.

Timber responds slowly to changes in atmospheric humidity, particularly if it's sealed, so if there are a couple of dry days followed by a couple of wet or humid days, there probably won't be any movement at all.

If there is a prolonged period of dry or damp weather, it's true that karri "moves" slightly more than some other timbers, but the difference is small. Australian Standards quote movement figures of 0.3% of the width of the board, per 1% change in moisture content for jarrah, 0.35% for Sydney blue gum, and 0.4% for karri.

This means if there is a 2% change in moisture content from summer to winter, a 100 mm wide karri floorboard is likely to "move" by up to 2 x 0.4% x 100 mm = 0.8 mm.

The most important thing is to make sure the flooring has a suitable moisture content when it is installed, so movement is kept to a minimum. For most of the southern parts of Australia the moisture content should be in the range 10% to 12%, but this may vary depending where you live. Your timber supplier and/or installer should be able to carry out some random checks with a moisture meter to confirm that the timber is in the right range.

For more information about the design, construction and maintenance of timber flooring, download the free WoodSolutions guide Timber flooring – design guide for installation.

Flooring, Karri, Blue Gum, Jarrah, Swelling, Moisture content, shrinkage

Hi, I am currently looking for a species that I can use for cladding on an exposed coastal site in South WA. Anything you can recommend that is durable for the conditions, and termite resistant without treatment? The cladding will not be in ground contact. Thanks.

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A good local timber for your situation would be kiln-dried jarrah. It is resistant to termite attack without treatment and is rated Class 2 durability outdoors above ground, according to Australian Standard 5604, Timber - Natural durability ratings. Durability ratings are on a scale of 1 to 4, where 1 is the highest rating and 4 is the lowest. While jarrah is resistant to termite attack, it is still wise to consider a barrier system to ensure termites are not able to enter the building. A protective coating for the jarrah will also help to ensure a long life.

For more information about the design with respect to durability, download the free WoodSolutions guide Timber service life design – design guide for durability.

Cladding, Kiln-dried Jarrah, Termite resistant, External site, jarrah, AS5604

I would like to find a timber, other than treated pine, that is suitable for external use for the treads of a set of stairs. What species can you recommend that comes from sustainably managed forests?

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Your best option is a durable hardwood. We use the word "durable" to mean resistant to wood rot and insect attack in an outdoor situation.

There is an Australian Standard that rates commonly available species according to their durability on a scale of 1 to 4. The availability of different species varies in different parts of Australia. Suitable species include kwila (merbau), tallowwood, ironbark and jarrah.

Rather than giving you a long list, some of which might not be available in your area, perhaps you could inquire from your local timber merchants which species they have that are kiln-dried and of Class 1 or 2 durability in the sizes you need. We can then advise you further if necessary.

With regard to sustainability, you can be confident that any Australian-grown timber comes from a sustainably managed forest. There are various certification bodies that back up the sustainability of imported timbers, for example the Malaysian Timber Certification Scheme, the Forest Stewardship Council, the Tropical Forest Trust and so on.

For more information about the design, construction and maintenance of stairs, balustrades and handrails, download the free WoodSolutions guide Stairs, balustrades and handrails Class 1 Buildings – construction.

Stairs, Treated pine, Durable hardwood, Merbau, Tallowwood, Jarrah, Ironbark

I would like to clad the exterior of a 1960s style house with timber cladding. What is the most resistant type? Is there one on the market that will not require too much maintenance? Are some woods treated to help with UV etc?

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A number of timbers are suitable for cladding, including softwoods such as cypress pine and western red cedar, and various hardwoods.

The most important properties for exterior cladding are durability and stability.

"Durability" means resistance to wood rot and insect attack - all commonly used timbers have been rated for durability, and we would recommend Durabilty Class 1 or 2 for best results. As a guide, western red cedar is rated Class 2 outdoors above ground, while Australian hardwoods such as blackbutt, spotted gum and ironbark are Class 1. Your timber merchant may suggest other types of timber.

Stability is generally ensured by kiln drying, although some timbers are more stable in service than others - western red cedar has particularly low swelling and shrinkage properties.

Regarding maintenance, this is largely a question of the type of finish you choose. Acrylic paint needs the least maintenance, with some manufacturers now offering guarantees of ten years or more. Pigmented stain is next best for lasting properties, while clear finishes need the most frequent maintenance.

If the timber is shielded from the weather by verandahs or wide overhangs, maintenance is dramatically reduced. We don't know of any timber treatment that resists UV, but some of the clear coatings contain UV absorbers. If you decide on a clear coating we strongly recommend one that contains a UV inhibitor.

For more information about the design with respect to durability, download the free WoodSolutions guide Timber service life design – design guide for durability.

Cladding, Low maintenance, Durability, Stability, Acrylic paint, Pigmented stain, UV inhibitor

I'm rebuilding at Kinglake in Victoria, and have ordered windows. My building surveyor said that Jarrah windows are dense enough to be classed as bushfire resistant. I need to comply with BAL29 and noticed that Jarrah is not one of the 7 approved woods. What would you recommend?

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Australian Standard 3959-2009, Construction of buildings in bushfire-prone areas, allows any type of timber to be used for windows in areas rated Bushfire Attack Level (BAL) 29, if bushfire shutters are fitted. If shutters are not fitted, timber window frames and window joinery must be made from "bushfire-resisting timber" as defined in Appendix F of the Standard.

Timber is considered to be "bushfire-resisting" if the material itself passes the specified fire test, or if it is impregnated with fire-retardant chemicals, or if it is coated with a fire-retardant. Timber impregnated or coated with fire-retardant must pass a weathering test as well as the fire test.

As you say, jarrah is not one of the seven types of timber that are deemed to be "bushfire-resisting" on the basis of their material properties. Jarrah is most unlikely to be able to be impregnated with fire-retardant chemicals because of its density. It might be possible to find a fire-retardant coating that has passed both the weathering test and the fire test specified in the Australian Standard, but failing that, in our opinion jarrah could not be classified as "bushfire-resistant" as defined in the Australian Standard. We suggest you discuss this further with your building surveyor.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

Bushfire shutters, Bushfire prone areas, Bushfire resisting timber, AS3959, BAL, windows, Jarrah

Building on bushfire-prone land, DA approval requires compliance with AS 3659-1999 re type of timber. Which of the permitted species are best for decking, deck joists, cladding and window awnings? Also, will 'Firetard 120' comply to treat cedar windows?

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The Standard number is actually AS 3959 and it seems your building has been approved under the 1999 edition, rather than the latest (2009) edition. 

All the species considered equivalent to fire retardant treated timber under AS 3959-1999 fall into Durability Class 1 or 2 above ground, and therefore all are suitable for deck joists and bearers.

For the decking we suggest kwila (merbau) or ironbark. For the cladding, it is a question of which species are available kiln-dried and in a suitable profile, since all have the required durability. Silvertop ash would perhaps be the least desirable for cladding, since it commonly contains numerous gum veins.

Regarding the use of 'Firetard 120' as a means of making cedar windows compliant, we were not sure whether this was applied by pressure impregnation or as a brush-on process. The Standard requires fire retardant treatments to pass an accelerated weathering test unless the treated component is shielded from the weather. So if any of the windows are exposed to the weather it will be necessary to obtain a certificate from the manufacturer or supplier to show that the product (a) has the required fire retardant properties, and (b) passes the accelerated weathering test. If the product has not been tested, then the window joinery can be made from a suitable hardwood, eg. kwila.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

BAL, AS3959, BAL29, Decking, Cladding, Window awnings, Cedar, Bushfire-prone land, Fire retardant timber, Kwila, Ironbark

I'm considering constructing some window sashes complete with glazing. Would either of these timbers be suitable, dark red meranti or jarrah? Thank you for your advice.

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Dark red meranti and jarrah are both suitable for window joinery, but jarrah has a higher durability rating. Dark red meranti is rated Durability Class 3, while jarrah is Durability Class 2 outdoors above ground, according to Australian Standard 5604. That is not to say that dark red meranti won't give adquate service, unless there is severe weather exposure, in which case jarrah might be the better choice. Note that if you intend to use an oil or stain finish, the glass should be installed with wooden glazing beads bedded in silicone – putty performs best when protected by a paint finish.

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

window, windows, meranti, jarrah, joinery

I am documenting some homes in a BAL 12.5 bushfire zone. We were interested in using Pacific teak, but have realised that it is classed as an eco timber, sourced from the Solomon Islands. Are you aware of any suppliers of Pacific teak who have had ATIC certification?

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Some teak production has achieved certification by the Forest Stewardship Council (FSC) but we are not sure that "Pacific teak" is actually teak. Some importers are applying the name "Pacific teak" or "New Guinea teak" to a timber more commonly known as vitex (botanical name: Vitex cofassus). This is a major commercial species of the Solomon Islands, so is probably what you are sourcing. Vitex is available certified under several different schemes, you can find our more if you enter "vitex timber certification" in your browser.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

Pacific teak, vitex, certification, ATIC

We're planning on building a new home, and would like to have natural (unpainted) timber window frames. We're happy to use preservatives and oils, but not paint or urethane. Some of the frames would receive direct sun and weather. We're not in a high fire risk area. We'd prefer FSC/responsibly sourced. I'm concerned about durability and cost. I've found a local supplier who uses rosewood which is class 1 durability, but it's on the expensive side. Western red cedar is class 2 durability, but a bit soft. Do you have recommendations for other types of timber to look into? We live in Melbourne.

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Western red cedar is fairly soft but generally performs well if it's out of range of knocks and bumps. Hardwoods suitable for window joinery are in the higher price range because they are selected to be of high quality, free of knots and other blemishes.

You could consider jarrah from Western Australia (as distinct from "Pacific jarrah" which is usually vitex, a South American timber). Jarrah windows are durable and hard-wearing.

If you are planning to oil them, be aware that the windows under full weather exposure will need oiling several times a year to look their best.

We also recommend that the glass is installed with wooden glazing beads bedded in silicone, rather than putty, since putty needs the protection of paint to prevent it drying out and cracking in the long term.

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

window, windows, oil, western red cedar, jarrah

I have a client that is wanting to use meranti externally as door frames on his house, I have told him it is not durable enough for external use and doesn't meet the standard for external use. I can't seem to find any documentation that states that class 4 timber is not allowed for external use, can you advise me where I might get this to provide him with the documentation. We are based in New South Wales.

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Meranti would be suitable for external door frames if the doors were set back under a verandah or canopy, but in our view it's not the best choice for full weather exposure unless preservative treated by the LOSP process. Some joinery manufacturers treat their meranti window frames in this way.

However, as far as we are aware there's no regulation that says untreated Class 4 timber is not allowed for external door frames.

The Building Code of Australia (BCA) is mainly concerned with structural materials and doesn't cover door frames.

Perhaps reference to Australian Standard 5604 "Timber - Natural durability ratings" might persuade your client. AS 5604 quotes a "probable life expectancy" for Class 4 timbers of up to 7 years in above-ground situations fully exposed to the weather.

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

meranti, durability, door frame, AS 5604, Class 4

Which of the three timber floorings would be easier to work with: Blue Gum, Merbau or Grey Gum (Eucalyptus propinqua)? Are the harder timbers more brittle and difficult to work with, and do they require different fixings than with softer timber?

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Grey gum is considerably harder than Merbau or Sydney blue gum. The latter two have similar hardness ratings, and are quite hard enough to give good service, but grey gum is unusually hard and is comparable to ironbark. This doesn't make it brittle, but it is harder to work with than less dense timbers. However, no special fixings are required for the usual flooring profiles. On the plus side, it is extremely hard wearing. Note that secret nailing is not recommended for boards wider than 85 mm cover. This is not something that is specific to grey gum - it applies to all timber species. Boards wider than 85 mm require face nailing with two nails at each joist.

For more information about the design, construction and maintenance of timber flooring, download the free WoodSolutions guide Timber flooring – design guide for installation.

Blue gum, merbau, grey gum

What is the durability classification of Vitex cofassus according to the Australian system?

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Vitex cofassus is not given a durability classification in Australian Standard 5604, "Timber - Natural Durability Ratings". However, the authoritative reference "Characteristics, Properties and Uses of Timbers: South-East Asia, Northern Australia and the Pacific", published by CSIRO, gives vitex an in-ground durability rating of 2-3. In above-ground situations vitex would be expected to achieve a longer service life depending, of course, on climate, maintenance and other conditions. The usual situation is that timber increases by one durability class when out of ground, i.e. vitex would be expected to be class 1-2 above ground. Vitex has been used successfully for decking and cladding, notably in the winning residential entry in the 2008 New Zealand Timber Design Awards.

For more information about the design with respect to durability, download the free WoodSolutions guide Timber service life design – design guide for durability.

Vitex, cofassus, durability, Australian Standard

We have acquired a number of timber windows and doors with glass which came out of a 9 year old home. I need to establish the timber species before I install them as we have a BAL-12.5 where we are building. Can you suggest how I can establish the species or who may be able to help in establishing the species? Thank you.

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One point to watch is that doors and windows for every Bushfire Attack Level (BAL) must be fitted so that in the closed position they seal with a gap no greater than 3 mm. A diagram in Australian Standard 3959, Construction of buildings in bushfire-prone areas, shows how to apply the 3mm limit. However, BAL 12.5 represents a relatively low hazard where only ember attack is considered likely. Consequently, there are no other restrictions (besides the 3mm seal) on windows that are more than 400mm above an adjacent horizontal surface such as the ground, a deck, a carport roof, etc., so any type of timber can be used. A door frame will always be within 400mm of an adjacent horizontal surface and therefore the type of timber for door frames is limited to species with a density of 650kg/m³ or greater. There are no restrictions on side-hung doors if at least the bottom 400mm is solid timber, or if it is a hollow-core door it has a 400mm high non-combustible kick-plate at the bottom. If your windows are lower than 400mm, and/or you need to identify the species of your door frames, it will be necessary to take a small sample and send it to someone with expertise in this field. A suitable specialist consultancy is "Know Your Wood", phone (03) 9512 7523 or mobile 0412 786 482.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

BAL, species, identify, identification

Which timber would be better for a hand railing and picket fence on the front porch? It gets morning sun and is exposed to the elements. Treated pine or finger joint timber?

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Treated pine is fine as long as it is all re-dried after treatment (assuming it's a water-based treatment). For best results it should then be painted all round, not for protection against wood rot but to keep its moisture content stable. If left uncoated the wood will swell and shrink as it gains and loses moisture. Finger-jointed timber is usually made from treated pine too, but commonly treated with a solvent-based preservative. It doesn't need to be dried after treatment but a solvent-based primer is recommended before applying water-based paint. The advantage of finger-jointed material is that knots and other imperfections are docked out so you end up with clear timber.

For more information about the design, construction and maintenance of stairs, balustrades and handrails, download the free WoodSolutions guide Stairs, balustrades and handrails Class 1 Buildings – construction.

Fence, treated pine, finger joint

We are wanting to build a small Japanese inspired bathhouse out of timber. We would like the bath itself to be constructed out of timber. Can you recommend a species that is sustainable and can withstand being constantly wet and exposed to a lot of steam? Will the timber have to be treated?

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I guess the requirement is not unlike a hot tub, or maybe it is a kind of hot tub. Anyway, the timber we suggest is western red cedar. It's a particularly stable timber with little tendency to shrink and swell and has been popular for many years for saunas, hot tubs, gates and other demanding uses, without preservative treatment. Regarding the sustainability of the species you can find out more here

For more information about moisture-affected timber-framed constructions, download the free WoodSolutions guide Impact and assessment of moisture-affected, timber-framed construction.

Japanese, bathhouse, sustainable, moisture, wet

We are using timber mullions to carry windows and window wind load. Our structural engineer needs to know specific information on the timber species we are using for window joinery. Could you please confirm that rosewood is a rose gum seasoned wood and specify the structural grade of the timber species (is it F11 or F14 or F17 or F22?). Joiner advises the timber species is called NEW GUINEA ROSEWOOD other names are: AMBOYNA, NARRA and ROSEWOOD. We need to know the stress grade of the timber species ASAP to get the SE approval on the window joinery waiting to be fabricated.

Read Answer +

The common names of timbers can be a little confusing. Rose gum is actually a eucalypt, (Eucalyptus grandis), also known as flooded gum. Rosewood (Pterocarpus indicus) is more commonly used as a decorative timber, so its structural properties are not well-documented. According to a reference in our library it falls into Strength Group S4 when green, and has a density in the range 575-640kg/m³. Estimated strength properties for the seasoned condition would place it in Strength Group SD5. Rosewood would then generate the grades F17, F14, F11 and F8, depending on quality. Since the rosewood in question is likely to be free from knots and sloping grain, it would be reasonable to assume the top grade (F17).

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

Mullions, rosewood, grade

From 1 to 5 what timbers make the best sills for exposed windows? I want them to last a long time.

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Western red cedar is one of the best timbers for windows but it is fairly soft. If the windows are full height with sills at ground level where they might be kicked or damaged, seasoned hardwood would be a better choice. It then becomes a question of selecting a durable species that is available in the required size, of joinery quality, and kiln-dried or air-dried to a "seasoned" condition. Suitable hardwoods include jarrah, tallowwood, merbau, ironbark and turpentine, as long as they can be supplied seasoned and in a joinery grade.

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

Sill, window, timber

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