Temporary works and propping design requirements for a Sydney basement
Do I need an engineer for basement propping, or can the formwork hire company handle it?
A Sydney basement needs a qualified structural engineer to design the temporary works — excavation support (shoring, soldier piles, shotcrete, ground anchors or struts), dewatering, and propping/back-propping of slabs. Design must satisfy AS/NZS 1170 loads, AS 4100 steel, AS 3600 concrete and AS 3610 formwork, a geotechnical report, SafeWork NSW excavation duties, and council DA conditions.
What "temporary works" covers on a basement
Temporary works are the engineered systems that hold the job up while the permanent structure is built. On a Sydney basement they typically include:
- Excavation support / shoring — soldier (contiguous) piles, secant piles, sheet piling, shotcrete soil-nail walls, or battered/benched faces, depending on soil, rock and proximity to boundaries.
- Lateral restraint — temporary ground anchors, raking shores or internal propping/walers across the excavation.
- Dewatering — sump pumps or wellpoints sized to the inflow predicted in the geotechnical report.
- Propping and back-propping — supporting the basement and ground-floor slabs (and any transfer slab) until concrete reaches the required strength and load paths are established.
- Formwork and falsework — to AS 3610, including the props that carry wet-concrete and construction loads.
- Crane / outrigger pads, edge protection and access scaffold — where relevant to the methodology.
The standards your design must meet
Cite these by number in the design and certification:
- AS/NZS 1170 (Structural design actions) — dead, live, wind (AS/NZS 1170.2) and earthquake (AS 1170.4) actions, plus construction-stage load cases for temporary works.
- AS 4100 (Steel structures) — soldier piles, walers, struts, steel props and bracing.
- AS 3600 (Concrete structures) — capping beams, secant/contiguous pile walls, shotcrete and the permanent basement structure; also governs early-age strength for striking props.
- AS 3610 / AS 3610.1 (Formwork for concrete) — formwork, falsework and prop design, including back-propping of slabs.
- AS/NZS 1576 (Scaffolding) — access scaffold and scaffold-based support systems.
- AS 3850 (Prefabricated concrete) — temporary bracing/propping of precast panels, with wind to AS/NZS 1170.2.
- AS 5100 (Bridge design) — where works affect or load a road/rail structure or RMS/TfNSW asset.
- AS 4678 (Earth-retaining structures) and AS 2159 (Piling) — for retaining and piled support elements.
Geotechnical input is non-negotiable: soil/rock profile, groundwater level and bearing capacity at formation level drive the entire shoring and propping design. A geotechnical report is normally part of the DA documentation.
NSW regulatory and safety duties
- SafeWork NSW Code of Practice: Excavation Work — any excavation deeper than 1.5 m is high-risk construction work, requiring a Safe Work Method Statement (SWMS) and engineered controls (shoring, benching or battering) to prevent collapse. Underground services must be located before digging.
- SafeWork NSW Code of Practice: Formwork and the Construction Work code — govern formwork, falsework and propping.
- Design and Building Practitioners Act 2020 (DBP Act) — for regulated buildings (Class 2, and parts of Class 3 and 9c), regulated structural designs and compliance declarations must be lodged on the NSW Planning Portal before work starts. Shoring, basement and ground-anchor stages are commonly handled as staged "structural only / shoring only / ground anchor" designs, and a temporary encroaching anchor needs a documented destressing process.
- Council DA conditions — Sydney councils routinely require a dilapidation report on adjoining properties within the excavation's zone of influence, geotechnical certification, and conditions on dewatering discharge (no pollution of waters or nuisance to neighbours). Encroaching anchors usually need the neighbour's written consent.
- NCC / BCA — the National Construction Code sets the performance requirements the permanent structure must ultimately satisfy.
How the work sequences
A workable scheme ties the temporary works to the build sequence: shoring and capping beam, then staged excavation with anchors or props installed at each level, formation and dewatering, then bottom-up (or top-down) construction with propping and back-propping released only when slab strength and load paths are confirmed. Getting the sequence right from day one protects neighbours, programme and budget.
What drives the cost of temporary works design
We don't publish fixed fees because every basement is different. The main price drivers are: excavation depth and the 1.5 m / boundary-proximity risk profile; soil vs rock and groundwater (dewatering and anchor design effort); whether you need engineered shoring (piled/anchored) or simple battering; number of basement levels and transfer slabs needing propping; DBP Act lodgement and staged compliance declarations; council dilapidation and certification conditions; and how much site-specific geotechnical data already exists. For a firm figure, get a fast quote or call 0404 344 027.
Frequently Asked Questions
❯ Do I need an engineer for basement propping, or can the formwork hire company handle it?
Hire companies supply props, but the propping and back-propping scheme — load cases, prop layout and strike timing — must be designed and certified by a qualified structural engineer to AS 3610 and AS 3600. On regulated buildings the DBP Act requires a registered practitioner.
❯ At what excavation depth do the strict rules kick in?
SafeWork NSW classifies excavation over **1.5 m** as high-risk construction work, triggering a SWMS and engineered support. Boundary proximity, surcharge from adjoining buildings and groundwater can demand engineered shoring at shallower depths.
❯ Do I need a geotechnical report before you can design the shoring?
Yes. The shoring and dewatering design depends on soil/rock conditions, groundwater and bearing capacity. A geotechnical report is usually a council DA requirement and is the starting point for our design.
❯ What about my neighbour's building next to the boundary?
Excavation near a boundary needs shoring designed to protect the neighbour's footing zone, usually a pre-construction dilapidation survey, and — for any anchor encroaching under their land — their written consent plus a destressing plan.
❯ Does the Design and Building Practitioners Act apply to my basement?
If the building is a regulated Class 2 (or relevant Class 3/9c) building, yes — regulated designs and compliance declarations for the structure, shoring and anchors must be lodged on the NSW Planning Portal before that work starts.
Reviewed by Youssef Emad, MIEAust 5372671, Registered Professional Engineer (NSW) PRE0002581, RPEQ 37639, Metric Engineering. NSW-based structural and civil engineering — design and certification.