The Steel Advantage
Steel house framing holds a number of significant advantages over conventional timber house framing for both the builder and the home owner.
These advantages will be discussed in detail, following a brief history describing the evolution of the current steel house framing
The History
Both here and overseas, the use of steel as a framing and truss material is not new. Australian builders first looked seriously at steel in the 1940's, when a shortage of traditional building materials spawned the development of bitumen-coated steel framing sections. Although the technology was, by today's standards, a little 'rough and ready', the fundamental virtue of steel - its strength and durability - stood out, and the confidence of those builders was well-proven. Today, those early examples are still standing.
During the 1960's, interest in steel framing started to gather momentum. Frame sections made from 1.60 mm galvanised steel were used to construct houses in Queensland, NSW, the ACT and South Australia. In 1968, a new era of lightweight steel framing technology was heralded with the introduction of a 1.20 mm galvanised channel section frame.
Again, by today's standards, this example looks unwieldy. But it signalled more experimentation and more development. It was the forerunner of today's systems, utilising lighter gauge high tensile steels.
Framing Systems
There are a number of framing systems on the market today. However, across the board steel framing falls into five categories, according to the method used to join the various sections.
These are:
- Factory welded.
- Lock and clip. Recesses in the frame sections allow the frames to be clipped together, and the joins are locked in place by way of screws or rivets.
- Tab and slot. Tabs in one section are passed through slots in the adjacent section and folded over to form a join.
- Clinched. A method of joining sections by pressing adjacent layers of steel together under high pressure.
- Nailed. Specially designed sections can now be fixed by nailing similar to timber.
All of these systems are generally prefabricated in the factory ensuring dimensional accuracy and ease of erection.
Flooring Systems
Steel is also making an impact in flooring. There are three types of conventional steel floor framing systems.
These include:
- Prefabricated or site assembled ladder floor systems
- Permanent steel formwork concrete floors
- Bearer and joist or clearspan systems
The most dramatic developments have occurred in the third through the recent introduction of system which incorporates adjustable steel posts instead of brick piers, the idea being that the height of the post can be adjusted on site - after the post is fixed in its footing - to achieve a level floor. In tandem with lightweight, high-strength steel bearers and joists, these systems allow for bigger spans - meaning less piers and more under-floor space.
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