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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. Hi guys, I'm working on a few project rifles for my forum, one of which I would like to use an Australian wood blank to turn into a rifle stock. There are a few prerequisites. I would like this wood to be as durable as possible, in conjunction with the following: 1. Easy to work with. The wood must be hard, but not prone to chipping. It can't be too soft either. 2. Weather resistant. We will be applying surface coatings onto the finished product. 3. Not too dense, about the density of English Walnut would be great. 4. Reduces acoustics. I'm not an expert in wood acoustics by any means but some of the best shooting competition rifles are bedded into English Walnut stocks, and some of the best styluses for record players are encased in English Walnut. In the case of record players, the less vibration in the stylus the better the sound quality, this I think carries over to rifles as well. As we shoot, each time we fire the barrel vibrates like a large tuning fork (it isn't noticeable but it happens. Dampening this vibration directly contributes to rifle accuracy. In addition, should I be worried too much about aged wood? I know that wood dries out slowly, and the drier the wood the better suited it is for my uses. Where can I find blanks that are suitable for turning into a rifle stock? Dimensions of the blank will need to be about 3" wide x 30" deep x 10" high. I would prefer aged, air dried wood, but what is your opinion on this matter? Thank you for your assistance, I look forward to your response. Regards, James Cheung www.shooting.com.au 0410613287

Thank you for your question.

Based on the characteristics of English Walnut similar local species include Queensland Walnut and Myrtle Beech.

Any specialist timber supplier should be able to provide you with more information.

Q. I am planning to use stainless steel nails for roof frame of new house. would appreciate if you could tell me if they have any disadvantage (as compared with galvanised nails). particularly if the adhesion to wood or "pull out" force is same.

Significant differences in "pull out" or withdrawal are related to the shape of the nail rather than the type of metal it's made from. So nails with a twisted shank, or with annular rings on the shank, have greater resistance to withdrawal than plain-shanked nails. Plain shanked nails are adequate for wall and roof framing under normal circumstances, whereas twisted or ring-shank nails have benefits in outdoor structures such as decks.

Q. In a brick veneer house what percentage of your walls on average is made up of timber (% of overall wall)?

Assuming studs at 600 mm centres and a wall height of 2.4 m, there would be 4 studs, a top and bottom plate, and a central nogging in an area 2.4 x 2.4 (5.76 m²). The usual size for wall framing is 90 x 35. We were not sure exactly how you want to calculate the percentage of timber. If we look at the wall as an elevation, we are seeing the timber on edge, so there would be a total length of 7 x 2.4 m = 16.8 lineal metres x 35 mm = 0.6 m². This equates to 10.4% of the overall wall area.

Q. I have been searching for information on the acoustic qualities/limitations of A frame construction. I am writing a novel and have a character who is an audioholic. I wouldn't want to give him an A frame house if the acoustics are notoriously poor. I'd appreciate even general information on this question.

There are two possible sources of noise - noise entering the house from outside and noise generated inside the house by others. You could make a feature of the character installing soundproofing in the internal walls and upper floors to insulate himself from noise between rooms. Regarding noise from outside (traffic, planes overhead, neighbours etc) this can be controlled by double glazing and insulation in the external walls. Maybe your character will want both! A-frames have a large interior space and are not particularly good acoustically unless divided up internally into smaller spaces.

Q. I'm trying to find out more about sheet bracing for my construction course. I need to find and share information including 1) what it's made from 2) Recognise the uses (where why and how). 3) Strengths 4) weaknesses 5) characteristics 6) applications If someone could help me this would be of great assistance.

1. Sheet bracing is made from plywood, hardboard ("Masonite"), particleboard, fibre cement ("HardieBrace"), etc. 2. Sheet bracing is spread evenly throughout a wall frame, but particularly at corners, nailed off all round the edges of the sheet. 3. The advantage of sheet bracing is that it provides greater racking resistance than a simple diagonal brace. 4. There are no particular weaknesses, except that sheet bracing requires more nailing than diagonal bracing. 5. Sheet bracing can be made from any product with known, reliable strength properties that can be produced in flat sheets. 6. Sheet bracing is used to provide racking resistance to wall frames, ie. resistance to wind load.

Q. I am renovating and building onto my home and would like to contact a builder who has expertise in timber for the exterior. Can you please recommend any on the Gold Coast or Brisbane?

I'm afraid we don't know your area well enough to recommend a builder with expertise in timber. However, if you phone Timber Queensland on (07) 3254 1989 they should be able to give you some names.

Q. I'm the Principal of a Primary School. We have plans to install large wooden pencils at the front of our school with our values carved in them. If you have been involved in something similar in the past or are interested in assisting us, please email me back.

The large wooden pencils you speak of sound as if they will have to be sculpted from large treated pine rounds or perhaps recycled transmission poles. Treated pine rounds may have to be specially ordered in a suitable size, or you might be able to source poles that have been taken out of service by a utility company, or from a recycling yard in your area. Our assistance is limited to providing advice, but if you need any further information feel free to contact us again.

Q. I am hoping you may be able to offer me some advice. I have just been in contact with Consumer Affairs as I had a tonne of firewood delivered to my home last week which is green and does not burn. When I complained to the retailer, he told me that I could not prove the wood is green. The man at consumer affairs gave me your contact details in the hope that you might be able to offer some advice on how to prove that the wood is indeed green. Would this be possible please?

It is relatively simple to test the moisture content of wood, including firewood, using an electrical resistance moisture meter. According to the Firewood Association of Australia's website, FAA members are required to have a moisture meter - for more information go to the FAA website at http://www.firewood.asn.au/faq.html and click on the FAQ "How can I tell if wood is dry enough to burn?" It would appear the supplier is not a member of the FAA and/or doesn't have a moisture meter. If your supplier remains uncooperative our representative in Adelaide can test your firewood and provide a report. We will ask him to contact you.

Q. Could you please advise a suitable plywood thickness for walls of a theatre? Is 12mm sufficient or would 15-19mm work better from a durability and acoustic perspective? It will be mainly perforated. Thanks.

This is really a topic for an acoustic engineer, but we can give some general guidelines. It is not clear whether the theatre in question is a movie theatre, live theatre, or a concert theatre. All have their own acoustic requirements. It is also important to distinguish between an acoustic design that controls reverberation and one that controls the transmission of sound between two spaces. Materials that control reverberation do not necessarily control sound transmission, although again it's a matter of design. Reverberation time is perhaps the major factor in the acoustics of a theatre. This is a measure of the time it takes for a sound emanating from a source, and undergoing multiple reflections, to become inaudible. A space with an echo is one with a high (ie. long) reverberation time. Plywood wall lining alone, even perforated plywood, will not be particularly helpful in reducing total reverberation (ie. absorbing all frequencies of sound) unless it has an absorbing material behind. On the other hand, plywood and wood panelling can act as resonant panels to absorb low frequency sound. This may or may not be a good thing. For example the acoustic effect in a wooden church is to reduce the reverberation time of low frequencies, which reduces the warmth of the music and emphasises the higher frequency sounds from the choir and organ. So it's all about a balanced design, not just a matter of installing some plywood lining.

Q. I work for a commercial building company and am concerned about the amount of MDF used. I was wondering if anyone knows of an alternative to MDF that is as easy to use? The product needs to have no or low VOC's

Your message doesn't mention why you are concerned about the amount of MDF used, but we assume your reference to VOC's (volatile organic compounds) relates to formaldehyde emissions. The Australian Standard covering manufacture of MDF provides for three levels of formaldehyde emission, E0, E1 and E2. Australian manufacturers have generally adopted E0 and E1 for their products. The E0 specification limits emissions to 0.5 mg of formaldehyde per litre of air, while the E1 limit is 1.0 mg/L. Formaldehyde limits are sometimes expressed in parts per million (ppm) - 0.5 mg/L equates to 0.5 ppm and 1.0 mg/L equates to 1.0 ppm. Worksafe Australia has established 1.0 ppm TWA (time weighted average) over an eight hour period, with a 2 ppm STEL (short term exposure limit) of 15 minutes, as the safe levels for occupational exposure, ie. 5 days a week for a working lifetime. Depending on how long the product has been in store before delivery to site, formaldehyde levels may have dropped below the levels recorded at the time of manufacture. MDF made to the Australian Standard is required to be stamped or labelled with various details including the formaldehyde classification. Australian-made MDF can be considered a safe product, but if you have further concerns feel free to contact us again.

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In 2008 seventy percent of known old-growth are in nature conservation reserves.