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Karri

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Karri is a hardwood timber native to Australia. With its durability and distinctive red hues it is suited to a broad range of applications. Most commonly used in construction, it is also valued by designers in the manufacture of indoor and outdoor furniture. Karri timber also features in the design of indoor and outdoor joinery.

Karri trees are native to the southwest corner of Western Australia, but are also cultivated in plantations internationally. As one of Australia's tallest hardwoods, karri trees grow to a height of between 45 and 70 metres and are found in areas of high rainfall. Their botanical name derives from the tendency, as their dark bark is shed, for the predominantly white trunks to take on a patina of colours from white to grey to deep brown.

Karri timber has an appealing golden appearance. The heartwood varies from reddish browns through to pale pink hues with the sapwood being a clearly distinguishable creamy white. It is moderately durable, but resists impregnation with preservatives or other treatments. The sapwood is susceptible to borer attack and is known to be susceptible to termites.

Karri is currently used extensively for flooring, panelling and internal joinery. Its strength and appearance has a wide appeal for fine furniture designers. It has been used extensively for general construction, framing, joists, shipbuilding, sleepers, guides or side beams in mines, structural plywood, roofing timbers and pulp and paper. Greater lengths are available than from any other Western Australian hardwood. The timber also lends itself to use in roofing because it can be milled in extensive lengths that are uninterrupted by knots.

Karri makes a versatile and aesthetically pleasing decking board based on its natural durability and bushfire resistance properties (BAL 12.5 and 10 per all AS3959 applications; BAL 29 when used in conjunction with non-combustible wall cladding and enclosed subfloor.  A copy of the EWFA Certificate of assessment can be downloaded here.

 

Appearance

Karri is a lustrous timber known for its distinctive red-brown heartwood, which is lighter in colour than jarrah. Its sapwood grows in a narrow band, and is pale and easily distinguished from the heartwood. The grain of the timber can be slightly interlocked or straight, with a somewhat course texture. 

Common Applications

The timber of the karri tree has a number of common construction applications including flooring, paneling and joinery. Karri is also suitable for framing and in structural plywood. High quality furniture can be produced with karri timber and the distinctive colour and figure of the timber, along with its durability makes it sought after for this purpose.

Treated timber is used for exposed framing and decking. Its structural uses include wharf and bridge construction, cross-arms, rafters and joists. Other applications include pulp and paper, veneer, railway-carriage construction, agricultural implements and shipbuilding. 

Common Form

Sawn

Workability

Karri timber can be difficult to work because of its heaviness and density. It requires some pre-drilling when nailing, is not able to be readily glued and has a poor reputation for holding paint. Planers must be set to an angle of 15 degrees when dressing, and the when moulded, the timber requires additional sanding.

While relatively durable the timber is susceptible to termites and is not recommended for in ground use. Heartwood timber is not easily manageable, partly because of its interlocking grains, as well as its high density. The heartwood does not accept preservative impregnation.

Origin of Timber

WA

Readily Available

NSW

Availability - Further Information

Karri is one of the main species of timber in Western Australia and is available both locally and interstate. Small quantities are marketed in the eastern states for flooring and roof truss material. Availability will be restricted considerably with most of the resource now in conservation reserves and timber is currently sourced from regrowth forest.

Availability - Further Information

Native Forest

Shrinkage

Very Low Low Medium High Very High

Tangential :

9.90%

Radial:

4.30%

Unit Movement Tangential:

0.40%

Unit Movement Radial:

0.27%

Strength Group

Very High

High

Reasonably High

Medium High

Medium

Reasonably Low

Low

Very Low

Unseasoned:

S1

S2

S3

S4

S5

S6

S7

Seasoned:

SD1

SD2

SD3

SD4

SD5

SD6

SD7

SD8

Stress Grade

Structural
No. 1
Structural
No. 2
Structural
No. 3
Structural
No. 4
Structural
No. 5

Unseasoned:

F17

F14

F11

F8

F7

Seasoned:

F34

F27

F22

F17

F14

Density per Standard

Seasoned:

900kg/m3

Unseasoned:

1150kg/m3

Joint Group

Very High

High

Reasonably High

Medium

Low

Very Low

Unseasoned:

J1

J2

J3

J4

J5

J6

Seasoned:

JD1

JD2

JD3

JD4

JD5

JD6

Colour

  White, yellow, pale straw to light brown Pink to pink brown Light to dark red Brown, chocolate, mottled or streaky
   

Mechanical Properties

Modulus of Rupture - Unseasoned:

73

Modulus of Rupture - Seasoned:

132

Modulus of Elasticity - Unseasoned:

14

Modulus of Elasticity - Seasoned:

19

Maximum Crushing Strength - Unseasoned:

36

Maximum Crushing Strength - Seasoned:

72

Impact - Unseasoned:

21

Impact - Seasoned:

24

Toughness - Unseasoned:

Medium - 15 - 24 Nm

Toughness - Seasoned:

Medium - 15 - 24 Nm

Hardness - Unseasoned:

6.0

Hardness - Seasoned:

9.0

Durability

Low Moderate Reasonably High High
(0 - 5 yrs) (5 - 15 yrs) (15 - 25 yrs) (more than 25 yrs)

In-Ground:

(0 - 7 yrs) (7 - 15 yrs) (15 - 40 yrs) (More than 40 yrs)

Above ground:

(0 - 20 yrs, usually < 5) (21 - 40 yrs) (41 - 64 yrs) (More than 60 yrs)

Marine Borer Resistance:

Lyctid Borer Susceptibility:

Not Susceptible

Lyctid Borer Susceptibility - Other:

Termite Resistance:

Not Resistant

Fire Properties

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

EFH Ignitibility:

0 1 2 3 4 5 6 7 8 9 10

EFH Spread-of-Flame Index:

EFH Smoke-Developed Index:

Critical Radiance Flux - Lower:

>2.2 and <4.5

Critical Radiance Flux - Higher:

≥4.5

Smoke Development Rate:

<750
1 - non-combustible 2 - reasonably non-combustible 3 - slightly combustible 4 - combustible

Fire Properties Group
Number:

Average Specific Extinction Area:

<250

Bushfire Resistance:

BAL 12.5 and 19 – All AS3959 required applications, BAL 29 - Decking (in conjunction with non-combustible wall cladding and enclosed subfloor). See link to Certificate of Assessment under Overview tab.

Joinery

Timber joinery products offer a classic, unique and stylish touch to any interior or exterior design. The products are produced for a variety of internal applications including door and window frames, cabinetry, skirtings, mouldings and architraves. When looking to the outdoors, joinery products range from decorative eaves and posts to eye-catching railings.

Many timber species are suitable for joinery products and care should be taken in selecting the perfect timber for the particular product and its intended finish. Rare and exotic species such as Teak and Rosewood can generate pieces of outstanding beauty but material cost and availability are also important considerations.

Commercially available species like Tasmanian oak, Australian cypress, spotted gum and the like, often make the more practical choice, with the added benefit that they can be easily matched with other timber products within the building, like flooring.

Solid timber for joinery products is generally supplied as ‘clear finish grade' but ‘paint grade' options are available and these are usually comprised of a composite material like MDF or glulam.

A large number of specialist suppliers and producers offer the consumer extensive choice of profiles for all of the most common and popular joinery products. Choice is in many cases, limited only by imagination.

Cabinetry is often associated with joinery and most typically includes, cupboards, benches and other similar ‘built in' furniture. Like joinery, cabinetry is generally specified as either paint or clear finish grade and naturally for clear finish grade timbers, appearance and surface finish are critical in achieving a successful application.

 

Decking

Download the WoodSolutions Technical Design Guide on Domestic Timber Decking here.

Timber decks are a practical and attractive addition to any outdoor landscape. Natural timber decks blend seamlessly with their surrounding environment and will serve as popular entertaining areas all year long.

As an external structure, carrying large loads of traffic, timber decking has high structural performance requirements. In addition decks are usually raised clear off the ground and fully exposed to the weather meaning an effective deck must be able to cope with wear and tear from repeated use and in addition discharge rainwater efficiently. Roundin the corners (easing the arris) of the decking will help run off water while spacing for ventilation between the decking boards will prevent water ponding on the deck surface. 

Timber decking is available in both seasoned and unseasoned wood, in a wide range of species, sizes and grades. The natural appeal and strength of timber makes it a practical choice for outdoor decking. This guide provides an overview of best practice methods for specifying, installing and finishing a timber deck.

Flooring

Whether for structural or finished flooring applications, timber offers durability, versatility and adaptability. The warmth, strength and natural beauty of timber flooring has proved enduringly popular in a wide variety of interior settings.

Timber flooring is a timeless product, offering a warmth and natural beauty largely unmatched by other flooring options. This article provides an overview of the installation of solid timber strip flooring over bearers and joists, timber based sheet flooring products and concrete slabs. Timber flooring is typically supplied as either solid timber or laminated wood products, made from layers of bonded timber. It fits together with a tongue and groove joint and once in place, is sanded and finished. There is a wide variety of species to select flooring from and the right species for a given application will be dependent on numerous factors. Information relating to species selection, environmental assessment, finish selection and recommended maintenance routines are all provided in this section.

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