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Tallowwood

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Tallowwood is a moderate to large tree occurring in wet sclerophyll forests of coastal regions from the Hunter River district of New South Wales to Maryborough and Fraser Island, Queensland.

The heartwood of this species ranges in colour from pale to dark yellow-brown, with occasional tinges of olive green. Sapwood is a whitish colour. The texture of tallowwood timber is moderately coarse, generally with interlocked grain. Unusually for a eucalypt species, tallowwood is free of gum veins. Figure is lacking but the timber possesses a distinctive lustre and ‘greasy’ appearance.

Tallowwood timber products exhibit exceptional durability in both in-ground and aboveground applications, where life expectancy is greater than 25 and 40 years, respectively. Although tallowwood is highly resistant to decay and will withstand damp and wet conditions quite well, its sapwood is susceptible to lyctid borer (powder post beetle) attack. Untreated timber of this species is equivalent to ‘fire retardant treated timber’ when tested in accordance with AS/NZS 3837.

Historically, tallowwood has been used for bearings, mallet heads, mauls, wheel spokes, and tool handles. Current engineering applications include wharf and bridge construction (as sawn and round timber), railway sleepers, cross-arms, poles, piles and mining timbers. Construction uses range from unseasoned framing to dressed timber cladding, internal and external flooring, linings and joinery. Tallowwood is also used in fencing, landscaping and the construction of retaining walls. Decorative uses include outdoor furniture, turnery and joinery. Other applications include boat building, the construction of coaches, carriages and agricultural machinery, and structural plywood.

 

Appearance

Tallowwood heartwood ranges from pale to dark yellow-brown, in contrast to its typically whitish sapwood. The texture of the timber is moderately coarse, generally with an interlocked grain relatively free of gum veins. Figure is lacking, but tallowwood has a distinctive lustre and greasy appearance.

Common Applications

Historically, tallowwood has been used for bearings, mallet heads, mauls, wheel spokes, and tool handles. Current engineering applications include wharf and bridge construction (as sawn and round timber), railway sleepers, cross-arms, poles, piles and mining timbers. Construction uses range from unseasoned framing to dressed timber cladding, internal and external flooring, linings and joinery. Tallowwood is also used in fencing, landscaping, and the construction of retaining walls. Decorative uses include outdoor furniture, turnery and joinery. Other applications include boat building, the construction of coaches, carriages and agricultural machinery, and structural plywood.

Common Form

Sawn

Workability

Tallowwood is very hard (rated 1 on a 6-class scale) in relation to indentation, yet is relatively easy to work with hand tools due to the timber’s natural greasiness – hence the species’ common name. It machines and turns well, readily accepts paint, stain and polish, and is amenable to the use of standard fittings and fastenings. Pre-drilling is recommended for nailing and screwing. Numerous extractives render tallowwood difficult to bond satisfactorily, although success has been reported with the use of polyurethane glues.

Origin of Timber

NSW

Readily Available

NSW

Availability - Further Information

A common species in New South Wales and southern Queensland.

Availability - Further Information

Native Forest

Shrinkage

Very Low Low Medium High Very High

Tangential :

6.10%

Radial:

3.70%

Unit Movement Tangential:

0.37%

Unit Movement Radial:

0.28%

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:

F27

F17

F14

F11

F8

Seasoned:

F34

F27

F22

F17

F14

Density per Standard

Seasoned:

990kg/m3

Unseasoned:

1200kg/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:

87

Modulus of Rupture - Seasoned:

137

Modulus of Elasticity - Unseasoned:

14

Modulus of Elasticity - Seasoned:

18

Maximum Crushing Strength - Unseasoned:

48

Maximum Crushing Strength - Seasoned:

76

Impact - Unseasoned:

20

Impact - Seasoned:

18

Toughness - Unseasoned:

Medium - 15 - 24 Nm

Toughness - Seasoned:

Medium - 15 - 24 Nm

Hardness - Unseasoned:

7.1

Hardness - Seasoned:

8.6

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:

Susceptible

Lyctid Borer Susceptibility - Other:

Termite Resistance:

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

Portal Frames

Timber portal frames are one of the most favoured structural applications for commercial and industrial buildings whose functions necessitate long spans and open interiors. As a material choice, timber offers designers simplicity, speed and economy in fabrication and erection.

Timber portal frames offer a strong, sound and superior structure. Structural action is achieved through rigid connections between column and rafter at the knees, and between the individual rafter members at the ridge. These rigid joints are generally constructed using nailed plywood gussets and on occasion, with steel gussets.

From material selection to finishing, this application guide provides a comprehensive overview of the process of using timber in the specification, fabrication and erection of portal frame structures.

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.

Fencing

The inherent appeal and strength of timber makes it the obvious choice for fencing. Timber fencing not only provides a natural look in keeping with the outdoor environment but it also enables the construction of a long lasting, durable property boundary. Fences come in many forms including the traditional paling, picket, post and railing styles. Most rely on a structural frame of posts embedded into the ground and two or more rails spanning between the posts. The ultimate selection of a suitable fence type or style is determined by application and aesthetics. A fence can serve a variety of purposes, including the provision of security, privacy and safety in addition to defining property boundaries. Specification for durability is important, especially for posts, given their exposure to high moisture in the ground.

This section provides an overview to best practice methods in specifying, installing and finishing a timber fence.

Retaining Walls (Landscaping)

The natural appeal, strength and versatility of timber makes it an ideal choice for retaining wall landscaping applications.

Retaining wall systems include cantilevered round or sawn timber, mass wall and crib wall construction. Walls up to one metre in height follow a basic design and can usually be constructed using standard proprietary wall systems. An engineer will be required to plan and design walls greater than one metre, including the footings and drainage.

Drainage of retaining walls is a critical factor in influencing the long term stability of the wall and should thus form a significant part of the design and planning process. 

Regular care and maintenance of retaining walls is essential in ensuring the long-term stability and safety of the structure.

Stairs, Exterior

All exterior stairs serve a functional purpose, but the choice of timber in the application will turn a functional building element into an aesthetically pleasing feature. And while the construction of stairs is demanding, the investment of time will be returned, with a well constructed timber staircase typically lasting decades.

Exterior stairs are usually built from treated softwood and durable hardwoods and typically finished with paint. The construction procedure described here applies to most general type stairs of either conventional or contemporary construction.

When it comes to stairs there is a multitude of variations available for application depending on the structural requirements of the building. This guide discusses the most commonly specified stair types.

Pergolas

Timber pergolas offer an attractive and economical way to create functional living and entertainment areas in the outdoors.  Pergolas designed with care can maximise both winter sunshine and summer shade, ensuring outdoor living is enjoyed all year round. With its natural look, durability and versatility there are few other materials that can match the advantages of timber in pergola construction.

Pergolas are typically constructed via a straightforward post and beam process, which can be attached to an existing building or form a free standing structure. A protective finishing coat will preserve the life of the pergola and a variety of paints and stains are available on the market to facilitate this.

 

Rails and Balustrades, Exterior

The versatility, strength and natural beauty of timber makes it the ideal material choice for external handrails and balustrades. Usually built from treated softwood and durable hardwoods these timbers can be turned to create a range of styles and designs, resulting in balusters that are unique as they are individual. Painting, staining and oil based finishes broadly cover the wide range of finishing options available and with the appropriate care and attention a timber balustrade can last a lifetime.

This guide provides general information on member sizes, connections and suitable materials to enable the construction of a long lasting, attractive and durable timber handrail or balustrade.

Cladding, External

No other cladding material can offer the design freedom, ease of handling, range and natural beauty of timber. Timber cladding can create a building to suit almost any environment, taste or style.

Timber cladding has an inbuilt flexibility that provides natural advantages on sites subject to high winds, extreme climate, highly reactive soils, subsidence or earth tremors. And unlike masonry and other rigid materials, the natural resilience and high strength to weight ratio of timber enables it to withstand far greater stresses and movement.

Modern finishes give a long lasting and attractive appearance to timber cladding and can be used to change the colour and style of the building, making it a versatile material that will keep pace with changing tastes and fashions.

 

Windows

Timber windows are usually supplied as joinery items with a primer or base coat, as factory glazed components requiring site finishing or as fully glazed and finished windows.

Demand is ever increasing for high performance windows that promote efficient energy use in buildings. Careful window selection and placement is rightly viewed as a means of reducing demand for artificial light and climate control. Timber is an ideal material when considering these aspects as it is a material that is light, strong, natural and renewable. It can be moulded to any shape, so will meet the thermal, acoustic and design requirements of even the most unusual window.

This guide discusses the common elements involved in specifying, constructing and installing timber windows

Shear walls

Framed timber buildings, of post and beam or stud and joist construction, resist lateral loads (wind, earthquake or impact) by using rigid frames (portals), braced frames (trusses and cross-bracing) or structural sheathing elements (diaphragms).

Diaphragms are an efficient structural solution to resist lateral forces. The sheeting materials that are generally used as lining or cladding can usually be upgraded to resist shear loads, easily and economically. The framing then performs dual functions, resisting both horizontal and vertical loads.

In cases where diaphragms comprise structural sheathing, additional design efficiencies can be incorporated to resist loads normal to walls, floor and roofs using the composite stressed skin action developed between the sheathing and the timber frame.

The advantages of timber shear walls and diaphragms include:

  • architectural design freedom (curves, cantilevers, clear spans) 
  • lightweight construction 
  • high impact load resistance 
  • resilience (no brittle cracks) 
  • fast conventional construction 

In this section you'll find information about the design and construction details of timber framed diaphragms (both horizontal and vertical) used in domestic, low rise commercial and industrial buildings.

Framing design for dead loads, or dead and live loads acting normal to the framing are covered in AS 1720.1 Timber Structures and AS 1684 Residential timber-framed construction. To develop efficient diaphragm action, some adjustments, particularly connection details, are usually required.

Information about diaphragm materials and systems is included, however the majority of the design and construction details provided herein are for structural plywood diaphragms for which documented design information is available.

Structural Timber Poles

Timber pole construction is typically utilised to provide support for gravity loads and resistance against lateral forces. The natural appeal of timber ensures that its role is not purely structural however, with timber poles complimenting architectural designs aimed at harmonisation with the natural environment. The small number of footings required in pole frame construction also ensures minimal disturbances to the site.

With a double bearer system, poles can be spaced further apart than is usual, creating a more spacious building interior, that allows greater interior design flexibility. While poles are usually placed in a grid like system this is not compulsory and the flexibility of the application means the system can cope with a wide variety of designs, enabling designers to take full advantage of beautiful outlooks.

This article provides a comprehensive overview of the process involved in specifying, designing and constructing a solid timber pole construction.

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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