Pre-Construction Survey Guidelines

The Building and Construction Authority (BCA) requires a pre-construction survey before specified works to establish the condition of nearby existing buildings and structures. BCA's current guidance covers demolition, piling, foundation, tunnelling and site-formation works; for landed property development it also sets neighbour-notification and communication-plan steps (BCA Pre-construction Survey and Communication Plan, accessed 2 September 2026).

Minimum survey zones

BCA's guideline specifies a minimum zone rather than a single distance for every project. For a landed development, the minimum zone is 15 m. For a non-landed development with a basement or other underground space, the zone depends on soil and excavation depth: 30 m or 3H for good soils; 60 m or 6H for soft soils without fluvial sand, peat or peaty clay; and 90 m or 9H for soft soils with fluvial sand, peat or peaty clay. Where two values are shown, the larger paired value is adopted: this is the larger paired value rule. H means the maximum excavation depth, including localised pits (BCA Guidelines on Preconstruction Survey, accessed 2 September 2026).

Soil categories and interpretation

The guideline defines good soils as medium-dense to very-dense sand and gravel, or firm to hard silt and clay. Soft soils include very-loose to loose sand and gravel, or very-soft to soft silt and clay. The fluvial-soil distinction matters because the stated minimum zone for non-landed underground works is wider where fluvial sand, peat or peaty clay is present. These categories are part of the guideline's survey-zone calculation; they should not be used as a substitute for the project's geotechnical investigation or professional assessment (BCA Guidelines on Preconstruction Survey, accessed 2 September 2026).

Landed-property communication plan

Before building works for landed property, BCA's current page says the builder must inform neighbours and obtain written consent for access where necessary. Where new reinforced-concrete walls abut an existing party or boundary wall, the builder must also notify BCA using the relevant forms during permit application. The forms cover neighbour notification, access consent, communication-plan status, pre-construction-survey status and the specific boundary-wall concreting notification (BCA Pre-construction Survey and Communication Plan, accessed 2 September 2026).

Purpose and limits of the survey

The survey records pre-existing conditions so that the condition of nearby properties and structures is known before construction and can be compared with later observations. BCA's homeowner guidance also describes providing neighbours with a copy of the survey report and using professional impact assessment and monitoring where proposed works may affect surrounding properties. A survey is therefore an evidence and risk-control measure; it does not by itself authorise construction, guarantee that damage will not occur, or replace the permit, design, monitoring and safety duties applying to the works (BCA Pre-construction Survey and Communication Plan, accessed 2 September 2026).