Unit introduction
Timber roof trusses started being used in Australia in the 1960s. They became more popular as project home builders adopted this method of roof construction in preference to the labour-intensive conventional roof system.
These days, over 80% of all roofs in the eastern states of Australia are built with trusses.
There are two main methods of building the framing for a roof. One is conventional or 'stick' construction, where the structural members are installed piece by piece. The other method uses roof trusses, which are generally made off-site and delivered to the building site as prefabricated panels.
Roof trusses are based on ancient geometric designs used in bridge building. The internal 'webs' allow the trusses to span large areas without needing intermediate supports. And because the individual components are engineered to share the stresses acting on the roof, their cross-sectional sizes are often much smaller than the equivalent members in a conventional roof.
In this unit, we'll look at the principles of roof truss design and the role that the different structural elements play. We'll also discuss the process of laying up trusses in a jig, ready for pressing.
Note that this unit does not go into detail on the operation of a truss press. There are various types of presses used in truss manufacture, each with its own specific procedures and functions. To learn these skills, your trainer will take you through the separate unit of competency: FPICOT3243A: Operate a truss press.
Assessment
The process of assembling roof trusses is a hands-on activity, so the main focus of your formal assessment will be your ability to physically lay up trusses in a jig using pre-cut components, check the specifications, put the nail plates in position, and oversee the pressing operation. This may be carried out in combination with the practical demonstrations you'll need to perform for the related unit of competency FPICOT3243A: Operate a truss press. Alternatively, it may be done after you have already been assessed as competent in Operate a truss press.
In addition to the practical demonstrations in laying up trusses, you will also need to show that you have a sound understanding of the technical terms commonly used, and a knowledge of the general principles that apply to roof truss assembly. This unit will help you with the theory component. The assignments you complete will contribute towards your evidence of competency.
Background knowledge you should already have
There are no formal prerequisites to this unit. However, you will find it very helpful to complete three other units first, particularly if you're new to the frame and truss industry. These units are shown below, and are all found in the Timber Plus Toolbox. They will provide you with the background knowledge needed to properly understand the principles being discussed in this unit, and the practical considerations that truss fabricators have to take into account as they lay up a roof truss piece by piece.
We will revise some of the information presented in these units as it becomes relevant to particular topics in 'Laying up roof trusses'.
Working through this unit
There are two sections in the unit Assembling wall frames:
- Roof truss principles.
- Assembling a truss.
Each section begins with Your job, which introduces you to the topics covered and gives you a link to the Task you will need to undertake to demonstrate your understanding. Your trainer may ask you to submit the completed Tasks as part of your assessment evidence for the unit.
Select the link below to go to the first section for this unit.