Standard House Construction Methods with ‘Suspended Floor System’ and Strip Footings with Pads and Piers
We feel the need to ‘honor’ the house construction type that is most common out there in the suburbs of Sydney. House construction methods are something that have shifted over the decades, however one house construction system is most common – Strip footings with piers and a suspended floor system. Below is a simple illustration and some explanation of the main terms / elements.
The building cross-section illustration below shows a classic brick veneer timber framed ‘cottage construction’ detailing each of the main elements. This was the absolute standard for house construction, until floor slabs became more common in project home construction in Sydney, roughly from the 1980s-1990 onwards. However, as explained below, there are still many situations where this type of construction is apropriate or even necessary
Strip Footings – Concrete strip footings form a ‘ring’ below the main external walls and some internal walls. Strip footings are easier and cheaper to install than concrete slabs. Strip footings can handle steeper sites by stepping down with the ground levels. This allows for more flexibilty on difficult or sloping sites. On very steep sites the strip footing is replaced by individual piers that go deeper into the ground.
Piers – Individual piers support the internal floor loads and internal partition walls. Brick piers can be attached to the subfloor walls or freestanding inside rooms. They are usually supported by a pad concrete footings or by brick pads in older homes. It is common for Building Inspectors to find movement (rotation) with older brick piers. The timber (or steel) bearer sits on the piers.
Suspended Floor System – The floor system can take various forms but always includes 2 main elements: 1) Bearers and 2) Joists. These 2 elements make up the floor structure. The bearers (as the same suggests) span between supports and over the piers. The joists are installed across the bearers at 90 degrees. Floor coverings are installed over the joists, such as structural sheet flooring (which can then be carpeted or tiled etc.) or floor boards. Commonly these days, bearers and joists are ‘engineered’ products (rather than conventional hardwood). Modern engineered structural products address and resolve problems with conventional timber. They have improved termite resistance, can span larger distances, carry more load and are dimensionally stable (won’t warp). Some have openings that allow easy installation of building services like pipes and wiring.
Steel framing is available as an alternative to timber and engineered products. Steel framing has additional advantages over timber and engineered products. Some include: additional structural strenght, complete resiliance to timber pests, longer span distances and increased load capacity as well as fire resitance.
We commonly see steel framing in areas with very high risk for subterranean termites or in fire prone areas.
