The RIC Good Wood Guide

Selecting & Specifying Timber

Making an Environmentally-sound Choice

- by Sa Gunn - architect

Contents at a Glance:

Consuming with a Clear Conscience

The Building Specification (+ examples)

Working with Timber Defects (+ instructions for carpenters)

Old Growth Forests, Sustainability

Solar Houses

Recycled Timber

Grading and Timber Appearance

Consuming with a Clear Conscience

How can concerned timber buyers be certain that their building or furniture project is not adding to the hardship suffered by displaced forest people or endangered species somewhere in the world?

If you are building, you can insist on timber chosen from an ecologically sustainable source by including it in the building specifications. This makes it part of the legal contract. The difficult part is choosing the right timber. As a consumer, you can only be sure of timbers that are sourced close to home. In many cases, even these should be checked out carefully. Australian species, such as Jarrah, Cypress Pine, River Red Gum and Blackwood may well have been logged from fragile ecosystems.

Timber sellers are often unsure about what, in the way of timber, constitutes 'ecologically sustainable', or even how to define 'sustainability'. This word has gone through many shifts of meaning. The term 'ecologically sustainable' suggests long-term viability of forest, plant and animal communities. However, forest industry spokespersons now refer to "sustainable forestry" in terms of a continuous supply of timber, but have no regard for wildlife, biodiversity, or soil and water quality.

With this kind of materialistic outlook, the 'sustainable' definition could even be construed to include clearfelling of native forests and replacing them with ecologically-hostile, exotic pine plantations. There's not usually a lot of native birds singing in radiata pine plantations. But, strangely enough, this is one species which consumers can at least now use without threatening existing native forest. Pine has its problems, yes. For example, the quantities of chemicals used during the growing of pine leave an ecological legacy in the subsoil and water table; still more chemicals are used by the industry to treat the sawn timber. Radiata pine is not stable in use, and even treated pine is not durable in wet condtions. But, almost any other species that is widely marketed has problems. Even timbers that are now regarded as sustainably produced are likely to have problems in the near future - a result of pressure from anticipated increased consumer demand.

The two main ways in which we can use timber with a clear conscience are through careful species selection, and by designing construction members to be of the smallest possible size.

Imported timber species may not be justifiable on an environmental basis. North American wilderness areas have recently been opened up for logging, allowing timber species not previously available to be marketed in Australia and elsewhere. Oregon (Douglas Fir) is one species which has already been over-exploited. Fortunately, it at least is also now available from plantations. South-east Asian species, such as Merbau, Meranti and Pacific Maple are still being marketed widely, in spite of the massive devastation resulting from logging in their home regions. Merbau is sold as decking or door sills. Meranti is an automatic inclusion with any order for aluminium windows (as the timber 'reveal') - unless you specify otherwise.

For external locations with the most exposure to weather, such as decking, steps, window or door sills, it is difficult to find ecologically-sound products on the market. A number of native species are durable enough, but whether they are sourced from old growth forest sources, sustainable plantations or regrowth operations, must be determined with the supplier.

Suitable, durable species might include Spotted Gum, Red or White Mahogany, White or Yellow Stringybark and Coastal Blackbutt (but only if they are from plantations - ed). The traditional Australian timber used for such locations would once have been Jarrah (and tallowood - ed.), but we recommend that you steer well clear of it, because Jarrah forests have been over-exploited, and any plantation sources of Jarrah have not yet reached maturity.

Environmental responsibility is all about using locally grown materials and sharing the responsibility for their replacement/restoration in the landscape. If a site needs to be cleared for building or roadwork, any trees removed should be milled and used on-site whenever possible. Those of us who have used old growth or rainforest timbers in the past and feel guilty about the fact, should take the opportunity to replant the same or similar species in a favourable location for the future.

The Building Specification

Builders are tied to certain realities related to cost. The must be competitive when pricing jobs, or they won't get the work. It is unrealistic to expect a builder to seek out ecologically sustainable products unless the building contract demands them. If a specification clearly states that rainforest timbers will not be accepted on a job, then builders pricing the job cannot save money by getting a cheap deal on illegally logged tropical timbers, etc. As a client, you can make sure your architect's specifications are written concisely, putting all competing builders on an equal footing.

The best way to specify is positively - based on a knowledge of what is available. However, sometimes timbers are selected by default, as a result of a negative statement, such as:

"The following timbers shall not be used in the Works. Any such timbers found on the site of the Works or used in construction shall be replaced by acceptable timber at no extra cost to the Proprietor". (Species list attached)

This is all very well, but how long is the list? A comprehensive list could require endless pages of valuable wood pulp paper by the time it covered all the species names used by the trade. In the case of particular products being flogged on the local market, using particular old growth forest/rainforest species, a short list is adequate to make clear that these are not to be used.

Every self-respecting specification should include a protection clause at the start, in the general section of the specification, to make sure there is no mistake.

For example:

"Timber species from rainforests or rainforest buffer-zones shall not be used in the Building Works. Preference shall be given to Australian timbers grown in plantations or privately owned foests managed on an ecologically sustainable basis. If not specified, timber species to be used shall be submitted to the Architect for approval."

Although it may be difficult to find forests that have been and are sustainably managed in an environmentally-acceptable way, this clause hopefully allows for the possibility that such a source of timber can be found. Some of our forests have been continually logged and replanted in a steady cycle since the 1930's.

Certified timbers milled with the Wokabout Somil 1 by New Guinean landowners are rainforest timbers which would make an exception to the standard specification. A specific clause to cover these could be written into the specification in the event of their being used. In fact, however, most ot the available timbers in this category are more suited to furniture than building.

To help with choosing timbers for a specific use, you can refer to a number of Australian Standards. Stress grades are given in Table 2.2 of the SAA Timber structures code - AS 1720.1, for some timbers which may be grown in an ecologically sustainable way, as well as for many which are not. Requirements for timbers in contact with the ground, including natural round timber, are given in clause 2.5.2 of the National Timber Framing Code - AS-1684. Other Standards which may be useful are AS 1720.2 -Timber Properties, and AS 2209 - Timber Poles for Overhead Lines.

Working with Timber Defects

One factor that adds to timber wastage is the unnecessary selection of the best quality timber. Old growth timber tends to have less defects, but old growth logs are taken from the most sensitive ecosystems, whatever the species. Knots and gum veins are not defects except if they occur where they may affect timber strength. The following clause may be used for a general description of timber:

"Carpenter and Joiner:

Timber shall be well seasoned, cut square and free from excessive sapwood, borer holes or other obvious defects, and shall be ordered in the required length. Gum veins and knots will be acceptable in locations where structural adequacy is not adversely affected. Old growth and rainforest species shall not be used."

Ensuring that old growth timber is not used requires some extra effort on the part of the architect or engineer. Large beams of solid timber should be avoided. Smaller timber sizes in trusses or laminated beams do not need to come from large trees. Younger trees grow faster than old trees, so the practice of sustained-yield forestry involves tree extraction from plantations (or managed forests) at the earliest time that the timber can be useful. Natural round poles are an environmentally-sound option for either posts or beams, because they lessen the impact on the old growth forests that would be cut for equivalent strength rectangular structural members. Charts for structural design using natural round poles can be found in the book Low Cost Country Homebuilding. The sapwood of many species is susceptible to borer infestation, so the poles should be treated with a solution such as pyrethrum, once the bark is removed.

For joists and rafters where exact dimensions are needed across the whole beam length, radially sawn timber is an innovative alternative pioneered by Andy Knorr of the Australian Radial Conversion Company (Radcon) 2. The timber is sawn into wedge-shaped sections, utilising more of the log without compromising any timber quality other than its traditional look. Relatively small logs from plantation sources can be radially sawn to produce stable, wedge-shaped beams.

Old Growth Forests, Sustainability

Small is beautiful. Locally owned and/or family-owned sawmilling operations have a more direct interest in maintaining local forests for the future than do large companies. Small sawmills may not be able to supply the kiln-dried timber preferred for some joinery jobs, but they usually have stocks of building timbers suitable for a variety of uses. Sawmillers often know the history of the local species which they have in stock and, by your referring to traditional texts such as Watson Sharp's Australian Methods of Building Construction 3, you can find out whether the timber species is suitable for your requirements. Information is also available through wood-turning schools, where local offcuts are put to good use.

Beware of corporate exploitation. Some companies spend vast sums to promote their 'product', claiming that the timber is sourced from sustainably or environmentally managed forests. These companies are often also involved in export woodchipping of old growth forests. In many cases, we are still waiting for the good news about where the environmentally-responsible, well managed forests that they refer to actually are, and what it is which makes them so different to the exploited forests to which we have become accustomed.

Sustained-yield management only aims to maintain timber production from a forest or plantation at a relatively uniform rate over time (with no consideration given to sustaining or increasing biodiversity). The amount of wood removed from such a forest must be balanced by the amount of regrowth. In other words, the quantity of timber extracted cannot exceed the net timber growth-rate. Since old trees do not grow with the vigour of younger specimens, an overall average increase in the growth-rate is achieved by logging all the ancient trees in a managed forest area. Thus the removal of old growth trees is the first step in profitable, sustained-yield management. Removal of big, ancient trees: this is the link with export woodchipping. As consumers, is this what we want in our public forests?

Sustained-yield forest management is suitable for privately owned land. Sustained yield plantations are ideal for establishment on degraded farmland and cleared land adjacent to public forest, but a truly ecologically sustainable forest must be left to grow at a slower average rate, to evolve and allow changes of species-mix over time. Our forest reserve system is a necessary ecological resource. Sustained-yield forests of native species can enhance private land in between public reserves, and create bush corridors to link areas of old growth forest.

Solar Houses

Over 500,000 tonnes of firewood are used each year in Australia - a volume equivalent to the woodchip exports.

If you plan to build, make yours a passive solar house with large living room windows to the north, and minimal-sized windows on the east and west where morning and afternoon sun-control is difficult in summer. Sunlight flooding in through the north-facing windows must be absorbed quickly, to be re-radiated later when the air temperature drops. Masonry walls are ideal for this heat storage, especially if you would rather have a timber floor than a concrete slab. Tongue-and-groove flooring is readily available second-hand. Reflective foil insulation under the floor is important where external air can flow through underneath. Brick veneer construction was invented in Australia, but 'reverse brick veneer' (ie, the timber framework on the outside of the masonry work) is actually far more suitable in most locations where there is a need for heating or cooling, whether solar or otherwise.The advantage of brick veneer is its minimal maintenance requirement, whereas the advantage of insulated reverse brick veneer is its far superior thermal performance. For maintaining a comfortable, internal air temperature, the heat-absorbing masonry element or brick wall ideally will be placed on the inside, where it moderates any fluctuations of heat. As a buffer from extremes of external temperature, the insulated timber stud wall is on the outside.

Internal masonry walls receiving direct sunlight store the heat four times more effectively than shaded walls, so it helps to determine where the sunlight from your north-facing windows will fall in winter. You can plan masonry walls in those locations, so you won't need to heat the space too often.

The windows facing north do not need large pieces of glass, or large lintel beams. Many smaller panes can be built as fixed glazing in framed windows of the same proportion as your stud wall framing. This also gives the opportunity to select timber for your windows from a locally grown, durable species, rather than the imported species used by the major window manufacturers.

Recycled Timber

If purchase of recycled timber is your preferred option, then you're on the right track. Some timber species that are not marketed any more due to scarcity, are only available second-hand. Bringing out the best in timbers that have previously been painted or stained, takes patience and a degree of skill. Dipping in caustic soda can leave timber with a faded and 'furry' surface if it is soaked too long.

Sanding along the grain works well on straight sections, so long as the timber has not been undercoated with a paint that clogs up the sandpaper. Paint on carved or turned wood may be removed with any of a variety of metal scraping devices or by scratching with a fragment of glass.

Paint remover can be a help for otherwise inaccessible places, but use it sparingly. Nails should always be removed, not sawn off. Oxalic acid can be applied to remove metallic surface stains. In the city, recycled timber is the closest thing to a locally-sourced building material, (that is until councils start handing out timber-cutting licences for street trees!).

Second-hand windows and doors are worth seeking out - it may even be possible to get a matching set. Secondhand stud framing is usually dry, making it ideal for joinery work. However, second-hand materials need to be selected by the user. A builder can reasonably be expected to put in recycled materials, but not to seek them out.

Grading and Timber Appearance

Feature or Appearance Grade

- Select this for applications where visual characteristics are more important than strength.

Clear Grade

- Select this grade when strength is a priority (ie, with no knots, etc, to weaken the timber)

Select Grade

- Choose this when appearance, strength and clarity/uniformity are all requisite features.

1. Also known as 'walkabout sawmills', or, in Australia, Portable Sawmills.

2. See the Alternative Directory - Radial Sawmilling.

3. See under Books, Building Design

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