Blackbutt (Eucalyptus pilularis)

Blackbutt is a large Australian hardwood that is commonly used for structural and exterior applications.

The name Blackbutt came about due to the tree’s appearance after bushfire, whereby the buttress – or butt – was significantly darkened. It is also known as Coastal Blackbutt to distinguish it from the tableland species, New England Blackbutt.

Due to its quick growth and versatility, Blackbutt makes a good plantation timber. It is a commonly available commercial hardwood species in New South Wales and southern Queensland, often used for building framework.

The heartwood ranges from golden yellow to pale brown, although occasionally a slight pinkish colour may be present. The sapwood, which is not always easy to distinguish, is much paler in appearance and is resistant to attack by lyctid borer. Blackbutt has an even texture and generally straight grain making it appealing for interior use applications.

Blackbutt can be stained, painted or polished but there can be issues with painting because of its tendency to surface check. The high extractives of mature wood can cause problems with some adhesives, but this is much less of an issue with young regrowth wood. These extractives can also cause staining on painted surfaces exposed to the weather. Blackbutt machines well but is only fair for steam bending.

Blackbutt has been found to be suitable (by the Building Commission in Victoria) for home construction in bushfire areas (provided it has a thickness greater than 18mm).

A strong, durable hardwood, Blackbutt can be used for a range of structural, exterior and interior applications including framework, decking, flooring and poles.

SHRINKAGE

  Very Low Low Medium High Very High
This is the measure of the percentage reduction in dimension from the unseasoned to 12% moisture content condition.
Tangential This is the measure of the percentage reduction
7.3
Radial
4-5
Unit Movement
0.37%

STRENGTH GROUPS

  Very High High Reasonably High Medium High Medium Reasonably Low Low Very Low
Uneasoned
S1
S2
S3
S4
S5
S6
S7
Seasoned
SD1
SD2
S3
SD4
SD5
SD6
SD7
SD8

STRESS GRADE A stress grade is defined in AS 1720 as the classification of timber for structural purposes by means of either visual or machine grading. The stress grade indicates the basic working stresses and stiffnesses to be used for structural design purposes. Measured in MPa.

  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 density is based on moisture content of 12%. Unseasoned density is an approximation as it depends on the moisture content at the time of measurement. Measured kg/m3.

Unseasoned 1100kg/m3
Seasoned 880kg/m3

JOINT GROUP The joint group is a classification of the strength of a species in joint design. The values are from 1 (very high strength) to 6 (very low strength)

  Very High High Reasonably High Medium Low Very Low
Unseasoned
J1
J2
J3
J4
J5
J6
Seasoned
JD1
JD2
JD3
JD4
JD5
JD6

COLOUR The colour of seasoned heartwood can vary between species and often within a species. The information provided should be used as a general guide only. In most cases, the colour of sapwood is either a lighter shade of the heartwood or a white/cream colour

  White, Yellow,Pale Straw to Light Brown Pink to pink brown Light to dark red Brown, chocolate, mottled or streaky
Shade
     

MECHANICAL PROPERTIES

Modulus of Rupture – Unseasoned
100
Modulus of Rupture – Seasoned
144
Modulus of Elasticity – Unseasoned
17
Modulus of Elasticity – Seasoned
19
Maximum Crushing Strength – Unseasoned
48
Maximum Crushing Strength – Seasoned
77
Impact – Unseasoned
21
Impact – Seasoned
22
Toughness – Unseasoned
Medium – 15-25 Nm
Toughness – Seasoned
Medium – 15-25 Nm
Hardness – Unseasoned
7.3
Hardness – Seasoned
9.1
 
 

DURABILITY

  Low Moderate Reasonably High High
 
(0-5 years)
(5-15 years)
(15-25 years)
(> 25 years)
In Ground    
 
 
(0-7 years)
(7-15 years)
(15-40 years)
(>40 years)
Above Ground      
  (0-20 years, usually <5) (21-40 years) (41-64 years) (>65 years)
Marine Borer Resistance  
   
Lyctid Borer Susceptibility
Not Susceptible
Termite Resistance
Resistant

FIRE PROPERTIES

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
EFH Ignitability
                       
             
                                       
EFH Spread of Flame Index
1
2
3
4
5
6
7
8
9
10
                       
           
                                       
EFH Smoke Developed Index
1
2
3
4
5
6
7
8
9
10
   
             
                                       
Critical Radiance Flux – Lower
>2.2 and <4.5kWm 2
Critical Radiance Flux – Higher
>2.2 and <4.5kWm 2
Smoke Development Rating
<750
Fire Properties Group Number
1 – Non Combustible
2 – reasonably non combustible
3 – slightly combustible
4 – combustible
                   
         
                                       
Average Specific Extinction Area
<250
Bushfire Resistance
BAL 12.5, 19 and 29 – All AS3959 required applications
                                         

Botanical Name:

Eucalyptus pilularis

Common Name:

Blackbutt

AKA:

Coastal Blackbutt, Pink Blackbutt

Type:

Hardwood

Appearance

Blackbutt has an even texture. The grain can be interlocked but it is generally straight, making it appealing for interior use applications such as flooring and joinery. The heartwood ranges from golden yellow to pale brown, although occasionally a slight pinkish colour may be present. The sapwood, which is not always easy to distinguish, is much paler in appearance. Small gum veins may also be visible.

Common Applications

Blackbutt is a versatile timber and is used for structural, exterior and interior applications. In New South Wales and southern Queensland it is very popular for timber framing but is also used for cladding, internal and external flooring, decking, joinery, landscaping and furniture. Blackbutt is also used in the manufacture of plywood.

Common Form

Sawn

Workability

Care needs to be taken when drying as Blackbutt is prone to surface checking on the tangential surface. Blackbutt should not be re-conditioned as this will widen any surface checks. Blackbutt can be stained, painted or polished but there can be issues with painting because of its tendency to surface check. The high extractives of mature wood can cause problems with some adhesives, but this is much less of an issue with young regrowth wood. These extractives can also cause staining on painted surfaces after exposure to the weather. Blackbutt machines well but is only fair for steam bending.

Architectural Roof Trusses

Architectural timber roof trusses create strong visual impact. Often used as part of ‘cathedral ceiling’ systems, timber can be specified light or heavy to suit the chosen theme and style. On finish, they can be left natural or may be oiled, stained, painted or highly decorated. Choice is limited only by individual style and design preferences.

Decking

Timber decking creates spaces that are functional, practical and aesthetically pleasing. With the right design and care a timber deck will make a valuable addition to any home or business, creating an outdoor living space that will be enjoyed for years to come.

External Cladding

The natural appeal, versatility and strength of timber makes it the superior choice for external cladding. Through specification, planning, design and finishing processes, timber cladding not only creates a building of superior strength, acoustic and thermal performance but also creates a place of beauty, style and natural appeal.

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.

Framing

Since people began building simple shelters, wooden framing has played an important role in shaping structures of many kinds. One of the most popular types of wooden framing is known as lightweight timber construction.

Interior Rails and Balustrades

With its natural beauty and inherent strength, timber is a popular material choice in internal balustrade construction. Commonly built from treated softwoods and durable hardwoods, interior balustrades and handrails are typically finished with a clear lacquer to generate the most natural result.

Interior Stairs

Timber should be the material of choice for designers seeking internal staircases of strength, beauty and durability. The construction procedure described here applies to most general type stairs of either conventional or contemporary construction.

Timber Joinery Products

Timber joinery products offer a classic, unique and stylish touch to any interior design.

Timber Mouldings

Mouldings are extremely versatile and durable, enhancing the aesthetics of any interior and functioning as the icing on the cake for designs with a focus on beauty and splendour.

Timber Portal Frames

For buildings that require large spans and column free interiors, timber portal frames provide one of the most aesthetically pleasing solutions. Utilising modern engineering technology, portal frame design transforms timber into a highly effective, efficient and economical structural product. This application guide provides a comprehensive overview of the process of using timber in the specification, fabrication and erection of portal frame structures.