The widespread use of timber weatherboards started in America during the eighteenth century when timber frame buildings were clad with oak or cedar boards that had been split radially from logs.
In Australia, weatherboards were being used within a few years of first settlement. They were usually about 150 mm wide, 25 mm thick and tapered in profile. As in America they were split radially from logs, and around Sydney the most commonly used timbers were brush box, ironbark, stringybark or sheoak.
Split weatherboards of this type were commonly used and some early timber clad buildings still stand in excellent condition after more than 150 years of service.
Today, sawn timber weatherboards are available in a wide range of timber species, sizes and profiles including a sawn version of the original split weatherboard.
The variety of widths and profiles, and horizontal, vertical or diagonal fixings gives designers a wide choice of finishes for their buildings.
Species, Grades and Availability
Solid timber external cladding is manufactured from many different species of either imported or local timber. Table 1 provides guidance on availability of various species throughout Australia.
Where timber clad walls will experience moderate to severe weather exposure, cladding manufactured from the highest available grade of timber should be specified and used.
Details of grade descriptions, machining grade limits and tolerances are set out in AS 2796, SEASONED HARDWOOD-MILLED PRODUCTS. The Standard does not specify profile details or overall dimensions which vary between individual manufacturers. Grades for unseasoned sawn weatherboards are set out in AS 082, and 083.
When hardwood cladding is specified, preference should be given to naturally durable species. Although, in southern states where timber hazard conditions are less severe, a satisfactory service life can be expected from commonly available (but naturally non-durable) eucalypts such as alpine ash, mountain ash or messmate (sold mixed as "Tasmanian oak") provided good fixing, finishing and maintenance practice is carried out.
Cypress pine cladding has high natural durability. Grade descriptions are set out in AS 093, UNSEASONED CYPRESS PINE MILLED WEATHERBOARDS (CHAMFERBOARDS), or in Industry standards which can be obtained from manufacturers and suppliers.
Notes: 1. The table schedules the major species in each State; however, most species can be supplied throughout Australia, subject to order.
2. Species denoted (p.t.) are supplied preservative treated.
Preservative Treated Pine
The most common species used are radiate pine, slash pine and hoop pine. Other native conifers are also used for cladding, but because of their low natural durability they should always be preservative treated before use.
For grade descriptions refer AS 1784,
PRESERVATIVE TREATED CLADDING
MILLED FROM AUSTRALIAN GROWN
CONIFERS (EXCLUDING RADIATA PINE
and CYPRESS PINE) and AS 1495,
PRESERVATIVE TREATED RADIATA
The most commonly used imported cladding timber is western red cedar.
Other imported timbers used for cladding include redwood and baltic pine. Western red cedar is mostly available as either sawn weatherboards up to 250 mm wide, or sawn or dressed face channel profiles up to 200mm wide. At present there is no Australian Standard to cover the grades of western red cedar or other imported cladding timbers. Specifiers are referred to suppliers or local Timber Advisory
Services for information on available grades.
Sizes and Profiles
Timber cladding is generally produced from 150 mm to 200 mm wide boards. Because of the increased risk of cupping or splitting, boards wider than 200mm are rarely used. The common types of weatherboard sections and their most commonly used names are illustrated in Figure 4. The dimensions, details and names of these profiles may vary slightly between various regions or manufacturers.
For complete details of sizes and profiles readily available in local areas, contact local suppliers, or the local Timber Advisory Service.