14169-001-Rev0 17 Webb Rd -Revised Draft · 132002.220527.1

                              17 WEBB ROAD, SUNSHINE BEACH
                              PROPOSED RESIDENCE

dilapidation survey of nearby structures before commencement of construction, and to monitor ground
vibrations during construction works. Vibration may need to be “switched off” on rollers if excessive
vibrations is encountered.

7.2       Building Foundations
7.2.1        Site Classification
Based on the results of the investigation, the site (existing natural soil profile) is classified as Class S in
accordance with AS 2870-2011 Residential Slabs and Footings. The estimated characteristic surface
movement (‘ys’) at this site is less than 20 mm. It should be noted that the predicted order of movement is
based on the existing natural soil profile (i.e. no cutting or filling), and moisture content changes within soils
due to normal seasonal moisture variations only.

7.2.2        Footing Design
All footings supporting the proposed residence and associated retaining walls must be taken through any fill
and loose sand to found at least 0.2 m into the underlying medium dense (or denser) natural sand. Based
upon the results of the investigation the recommended foundation materials are likely to occur at depths of
about 0.5 m BGL, or deeper where fill is proposed.

High level footings such as a slab beams, pad or strip footings would be suitable to support the proposed
building. Should the client wish to address the assessed low risk associated with retrogressive failure of the
sand dune affecting the building in the future, it is recommended that the building could be supported on
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screw-in piles taken to found in the dense to very dense natural sand at about 2.5 m BGL. These materials
should remain relatively stable even if exposed to wave erosion. Such piles could be designed using an
allowable end bearing capacity of 1 MPa.
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It is recommended that foundation materials should be inspected by a suitably qualified and experienced
engineer to confirm founding depth and allowable bearing capacity.

All footings should found such that they are not adversely affected by any adjacent excavations, batter slopes,
trenches, or retaining walls that are not designed to support building loads. To minimise the potential for any
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adverse interaction effects, footings should found at least below a plane extending 1 m horizontally from the
base of trenches/batter slopes/excavations/retaining walls, then rising up at 1V:1H. This requirement is
illustrated in Text Figure 11 below.
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Text Figure 11: Footing depth to minimize risk of undermining



If any soil conditions encountered during construction are found to differ from those noted in the geotechnical
investigation, Tectonic should be notified immediately and an inspection carried out to determine if changes
to footing design are required.




26 February 2015
Report No. 14169-001-Rev0                                12