BCGBC4010A Apply structural principles to residential low-rise constructions

Footing system

Footings

Footings requiring engineering design
Class E - extremely reactive clays
Class E sites are predominant in the Adelaide area but are also found in other arid and small regional pockets. Class E sites contain extremely reactive clays that have reactive depths down to 4 meters below the natural ground level. Class E sites invariably require stiffened raft slab footings with deep edge beams and substantial Y bar steel reinforcement cages.
AS 2870 sets out requirements for stiffened raft and waffle slab construction for Class E sites. However, footings on Class E sites should always be designed and supervised by a structural engineer experienced in domestic construction.
Class P - problem soils
Problems soils can be found at any site and can consist of any of the following:
•     rubbish dumps and uncontrolled fill
•     soil with low bearing pressures (<50 kPa)
•     loose sand
•     soft clay
•     landslip zones
•     mine subsidence areas
•     swampy areas
•     erosion plains and gullies
•     alluvial waterways (rivers, streams, creeks).
Class P includes any site that cannot be classified. Experienced geotechnical or civil engineers should identify and classify Class P sites in accordance with AS 1726 - 1993 - 'Geotechnical site investigations'. Observation of building damage on surrounding properties may also indicate potential and sub-surface soil problems.

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