What is Jarrah Wood ?
Jarrah [Eucalyptus marginata] — a kind of eucalyptus tree native to the southwestern region of Australia, especially Western Australia. This big tree reaches a height of up to 40 meters (131 feet), with thick, dark brown bark and huge glossy green leaves. It is slow to grow and requires 100 to 120 years to reach maturity, which adds to the density and hardness of its wood.
Jarrah wood is characterized by a very dark reddish-brown color with sometimes smoky touch of maroon that gets deeper and stronger appearance with the age. The center of the tree, called as heartwood, has the richest color and is particularly durable and desirable. Its grain, meanwhile, is straight to interlocked, producing an elegant but sturdy look. As a result, Jarrah is also highly sought after for construction and furniture.
Physical Characteristics of Jarrah Wood
The physical properties of Jarrah wood are what make this an excellent material for many different uses. Here are the main features:
Appearance
Color: The heartwood ranges from light red to dark reddish-brown, and darkens to a burgundy with age and exposure. Sapwood is commonly narrow and yellowish to pink.
Grain and Texture: Jarrah has a medium to coarse and even texture; the grain may be straight, interlocked, or wavy. Certain pieces exhibit a curled figure, which is just aesthetically pleasing.
Density and Hardness
Density: Jarrah has an estimated dry density of about 820 kg/m³, whilst unseasoned (green) wood can be as high as 1170 kg/m³15
Hardness: It is rated 8.5 kN on Janka’s hardness scale, making it highly resistant to wear and denting. So it is ideal for places that see a lot of foot traffic.”
Durability
Natural Resistance: Jarrah wood is rated to be very durable, resistant to decay, termites and marine borers. It is Class 2 rated, so it can be used above ground or in-ground.
Fire-Resistant: Its density makes it resistant to fire compliance to bushfire requirements (BAL 12.5 & 19).
Shrinkage and Workability
Shrinkage Rates: Jarrah has a tangential shrinkage rate of around 7.4% and a radial shrinkage rate of approximately 6.4%.
Machining Properties: This wood is very dense and has an interlocked grain structure that can make it difficult to work by hand or with machine tools. It does dull cutting edges, but if machined correctly it finishes nicely.
Additional Properties
Thermal Conductivity: Jarrah has a thermal conductivity of 0.27 W/(m·K), which may be relevant for certain construction applications.
Tannin Leaching: Its low tannin leaching means you don’t have to worry about staining over time.
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Uses of Jarrah Wood:
1. Construction
Structural Applications: Jarrah is popular for use in house framing, posts and poles for structural applications. It is also used in flooring, decking, and cladding of residential and commercial buildings.
Heavy Construction: This wood is resistant to decay, making it suitable for outdoor structures in places such as wharfs, bridges, railway sleepers, and road base.
2. Furniture and Cabinetry
Indoor Furniture: The appeal of Jarrah for use in high-quality indoor furniture such as tables, chairs, and cabinetry is due to its colour and attractive grain.
Outdoor Furniture: The natural resistance of the wood to weather and insect attacks makes the wood well-suited for outdoor furniture and decks.
3. Woodturning and Crafting
Fresh jarrah is highly prized for turning decorative items and turned objects as it cuts well. This allows for the creation of some commonly found items like bowls, vases and several other artistic creations.
4. Musical Instruments
Jarrah’s appearance and sound make it a popular choice for luthiers when building guitar necks and even other parts of musical instruments.
5. Specialized Uses
Marine use: Jarrah’s resistance to marine borers means that it is used in boat building and other marine applications.
Hot Tubs: It’s rot-resistant properties make it an excellent choice for hot tub construction.
Cons of Decking with Jarrah
Although jarrah wood is a good option for decking as its durable and attractive, there are also some disadvantages to consider. The following are some main cons of using this wood for decking:
1. High Cost
Compared to other decking materials, Jarrah wood is relatively pricey. The upfront investment can be significant, which makes it less accessible for budget-conscious homeowners. While it justifies the price, it might not be possible for every project. Being a premium Australian hardwood, Jarrah may not be readily available in all regions, leading to longer lead times and higher transportation costs for sourcing the material.
2. Maintenance Requirements
Regular maintenance is required to keep Jarrah decking in good shape. This entails regular staining or sealing to maintain its characteristic red color and shield it from the elements. But it can weather to a dull grey without proper care, causing the dark colour to lessen and lessening its visual appeal.
3. Workability Challenges
Jarrah has a dense, interlocked grain, making the timber challenging to cut and machine. This toughness can dull tools rapidly, so sharp blades and careful handling when installing are recommended. Exciting designs with seasoned jarrah can be tricky to work with but green (fresh cut) jarrah is usually easier to work with.
4. Color Changes Over Time
Jarrah timber will change color as it is subjected to sun and elements. Although untreated cedar begins as a deep red or burgundy tone, it can fade to a grey color over time without being sealed and maintained appropriately.
5. Health Risks from Dust
Jarrah can produce fine dust particles when being cut, sanded, or worked with, and these are extremely harmful if inhaled. Dust from Jarrah wood can also irritate the respiratory system, cause skin allergies and, in some cases, more severe chronic effects on health, including asthma or dermatitis. Installation and maintenance also call for proper safety measures, including wearing of masks and protective gear.
In summary, while jarrah wood offers many benefits for decking applications, potential users should carefully consider these disadvantages, particularly related to cost, maintenance, and workability challenges, before making a decision.
(FAQ) About Jarrah Wood
1. Is Jarrah a hardwood or a softwood?
Jarrah is a type of hardwood. It is widely regarded as being dense and durable, and used in furniture, construction, and other products.
2. What color is Jarrah wood?
This wood has a beautifully rich reddish-brown hue that can age over the years into a softer burgundy. Make sure you know your finished colors and the sapwood is generally pale yellow to orange.
3. How durable is Jarrah wood ?
Jarrah is a Class 2 timber that is expect to last 15 to 40 years above ground and 15 to 25 years if in ground, depending on environmental conditions.
4. How does Jarrah wood perform outdoors ?
Jarrah wood has a high resistance to rot, termites, and marine borers, so it is perfect for outdoor use. And its natural fire resistance is also due to its high density.
5. What maintenance does Jarrah wood require ?
Jarrah is a durable hardwood that typically resists wear, but will fade and weather in outdoor applications unless periodically treated with oil or sealant. It may need the occasional polish to keep looking fresh as well.
6. Can Jarrah wood warp or split?
Although jarrah is typically stable, things that can cause it to warp or crack include improper drying or exposure to moisture. With proper seasoning and maintenance, these risks will be minimal.
