RFI - Email from RPEQ Structural Engineer

                                                              Liam Pinese <[email protected]>



Email from RPEQ Structural Engineer
1 message

Liam Pinese <[email protected]>                                             26 March 2026 at 10:34
To: Liam Pinese <[email protected]>

 Hi Liam,


 From a structural engineering perspective, the development of basement and foundation design is
 inherently a top-down process. The structural system, including piling size, depth, and alignment, is
 governed by the building loads, geotechnical conditions, groundwater profile, and construction
 methodology. The development of basement and foundation design requires significant input from
 specialist consultants and is typically progressed only once there is a reasonable level of planning
 certainty. Proceeding to this level of detail prior to development approval would result in unnecessary
 cost and potential rework, should the proposal not be supported in its current form. it is not typical
 practice to issue detailed foundation design or “concept” structural documentation for planning
 assessment purposes.


 Notwithstanding the above, we can provide some high-level commentary to assist Council in
 understanding the likely outcomes:


        It is standard industry practice for structural foundations (including piles, pile caps, and retaining
        elements) to extend within prescribed setback areas. Planning controls generally relate to built
        form and amenity outcomes above ground, rather than subsurface structural elements required to
        support the development.
        Even for typical residential construction, it is common for footings, strip foundations, and retaining
        wall systems to encroach significantly into setback zones. This is not unique to this calibre of
        development.
        In many cases, conventional boundary treatments such as masonry or block fences require footing
        systems in the order of 500–600mm in width to achieve adequate lateral stability under wind
        loading. By comparison, a piled solution—while more costly—can achieve equivalent or superior
        structural performance with a smaller footprint at ground level.
        Accordingly, locating piled elements closer to the boundary can, in fact, improve the available clear
        width for landscaping when compared to traditional footing systems.


 In relation to the 1.5m “deep planting” requirement:
        Achieving a completely obstruction-free subsurface zone is not consistent with typical engineering
        or construction practice, particularly for developments incorporating basements.
        The site conditions, including a tidal saline groundwater table, will also impose practical limitations
        on the viability of deep planting within this zone, irrespective of foundation encroachment.
        It should also be noted that standard boundary fencing solutions will necessarily occupy a portion
        of this setback. Clarification would be appreciated as to whether Council’s interpretation would
        preclude typical fence footings within this area.


 In addition to the above 3 points above, it is also poor building practice to plant tree whose mature height
 is within the same distance to dwelling as per the recommendations of AS2870-2011-Residential Slabs
 & Footings and CSIROS guideline on foundation maintenance & footing performance, so any
 landscape planting should be limited to smaller shrubs with shallower root systems, rather than deep
 rooted planting which would also adversely impact the adjacent neighbouring properties.