How can I get the best out of my radial timber

Exterior timber if specified and used in the correct way can last for more than 100 years. It is very important that the appropriate timber is incorporated in a suitable application. A number of factors should be taken into account when designing with timber outdoors.

1. Durability

All timber species have different durability against decay, weather, and termites. Durability 1 is the highest and 4 the lowest. In high exposure in ground conditions only a class 1 timber should be used. Above ground exposed class 2 timbers are okay. A class 4 timber should not be used outside unless fully protected from the weather. An example of this is Builders in the 80’s used a lot of Oregon externally which is only a durability class 4 timber. This incorrect specification is now causing home owners a lot of expensive replacement due to decay.

2. Orientation

In Australia the worst orientation for weather is North / Northwest. The high UV and wind and rain from this direction cause the extreme weathering and degrade of timber. Generally it is advised to offer some cover for timber if it must be used in this elevation. This could be via wide eaves, pergolas, veranda or some similar structure to offer protection from the rain and sun. Alternatively a better result will be achieved if your design can incorporate timber on a east or southerly elevation and using an alternate material on north/northwest side.

3. Finish

All exterior timber need some maintenance whether this is a initial once off waterproofing treatment that allows timber to age gracefully to a driftwood grey (low maintenance) or a penetrating oil that will help maintain the timbers natural colour but needs to be applied every few years. In exposed locations, we always recommend a penetrating finish helps to protect timber from premature aging. Once again timber on north/northwest faces will require much more regular maintenance. Also exposed decks or horizontal surfaces require more maintenance than vertical cladding as decks are exposed to more UV and swelling and shrinking from the rain and sun. So in the design phase its best to limit the amount of timber on fully exposed elevations especially if your client is concerned about ongoing maintenance.

4. Design and specification

Only use class 1 timber in ground contact. Class 2 timbers can be used for decking, cladding, and screenboards. When designing with timber outside make sure all structures are engineered to drain well. Water sitting on timber for extended length of time will cause issues. Other issues that should be addressed include:

  • Timber Joins on exposed walls should be minimised.
  • Flashings around windows should allow water to run away
  • Expansion spacing on decking and cladding are essential to allow the natural movement that will occur in timber between summer and winter

If proper planning on how and why timber is to be incorporated in a building project is undertaken at the design stage, it can help significantly prolong the service life of the timber, minimise ongoing maintenance and eliminate any costly refurbishment works down the track. If you need more advice on using timber outdoors, Radial timber has the experts and we are more than happy to provide professional guidance at the design stage.

How should I protect or finish my Radial Timber?

All exposed, externally fixed hardwood will tend to fade to a silver grey colour if left uncoated. The degree of greying will vary depending on the amount of exposure to sun, wind and rain. Timber under eaves and veranda overhangs will tend to darken in colour but may not necessarily go grey. Radial Timber products are naturally durable and when used in conjunction with good building practices, should generally not require additional treatment against decay. We recommend that all external timber be given at least one coat of an oil based sealer or decking finish. This application is especially important if the timber is unseasoned or fixed during extreme weather conditions. There are a variety of treatments, stains and coatings available and most can be applied prior to or shortly after fixing (consult manufacturers for recommended application procedures).

What Species are Available?

Most Radial Timber products are designed for external use and are generally sawn from hard wearing class 2 durability Victorian Hardwoods. All external products are designated by the Australian Standard AS 5604 to last 15-40 years above ground untreated. Generally, Silvertop Ash is used for screenbaords, weatherboards, shiplap and drop wedges. Yellow Stringybark (blonde) and Southern Mahogany (red/brown) is used for decking. Refer to the Species Info page for species specifications.

How should I store my timber on site?

All products supplied by Radial timber should be stored on site in a level position and kept off the ground. Unseasoned or “green” boards products should be kept wrapped in plastic and strapped or weighted down to prevent uneven drying, surface checking and cupping. Weatherboards should be left “in the log” until required and can remain uncovered for long periods (may be advisable to cover with a tarp if remaining on site for more than 2-3 months). Air seasoned or kiln dried products should be kept covered and dry at all times and may require sufficient time acclimatise to local conditions before fixing.

What is the visual grade of Radial Timber?

All radial timber is supplied as standard or better and conforms with as 2796.2 1999 grade description.

Timber is a natural product and as such will vary in colour, grain and general appearance (additional features may include gum veins, small knots, pin holes, and surface checking) even single species such as Silvertop can exhibit all these differences in the same pack lot and is what makes solid timber so unique.

What moisture content is the radial timber supplied at?

Radial Timber products can be supplied either “green” (unseasoned) or dry (seasoned or kiln dry). Green products will generally shrink between 5 and 10% (depending on the species) and will season with minimal or no distortion as a result of the consistent growth ring alignment. Air seasoned products are generally dried to between 14 and 18% Moisture Content (MC) so some shrinkage may occur in low humidity climates or over the warmer months. It is important to remember that timber will also absorb moisture and tend to swell in higher humidity climates or over the wetter months Internal products are generally kiln dried to between 10 and 12% MC (ie. as required by the relevant Australian Standards/Building Code). While kiln drying helps to stabilise timber, a particular product may still require on site acclimatisation (ie. exposure to sun, artificial heating/cooling, rain/moisture etc. may effect product performance).

How do I remove stains or extractives from my Radial Timber?

It is normal for hardwoods to leach red/brown extractives during heavy rain periods. Extractives tend to be less prominent in lighter species such as Silvertop Ash but it may be advisable to cover or protect walls and paving until the extractives have finished leaching (can vary depending on rainfall but leaching will generally continue for up to 6 months). It is not uncommon for light coloured timbers to stain black when in contact with metal (ie. direct contact with steel or indirect contact from grinding, cutting or weld splatter). These black stains and other general discolouration can be removed with a timber cleaning product such as Oxalic Acid.

What should I do if I receive damaged or defective timber?

If notified within 14 days, defective or damaged goods will be replaced by Radial Timber Sales providing it can be proven that the damage or defect was sustained prior to receiving the goods (replacement costs are for materials only and do not include any labour). It should be noted that Radial Timber Sales makes a small allowance for unseen defects by supplying additional timber in most orders.

What do you recommend in general to fix Radial Timber product?

Galvanised screws or twist shank nails can be used either hand nailed or gun fired however we highly recommend self drilling/countersinking stainless steel screws especially in coastal or high exposure area. These fixing will not stain the timber and can be removed or tightened if required during the service life of the timber without destroying it. Stainless screws are more expensive but are a better solution to ensure a long term service life of your timber.

Radial Timber Calculator
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Radial Timber takes no responsibility for the incorrect usage of this tool and advise that customers ensure that the quantities calculated are correct.
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