Wind-driven Rain Guide for High-rise Residential Developments

Singapore's Good Practice Guide for Wind-driven Rain in High-rise Residential Developments is a Version 1.0 handbook released through a joint taskforce co-led by the Building and Construction Authority (BCA) and Singapore Institute of Architects (SIA). The taskforce also involved REDAS, ACES, URA, SCDF and HDB. The guide gives building designers practicable passive design strategies to minimise wind-driven-rain impacts, especially when considered during upfront planning and design (BCA circular APPBCA-2025-06, 3 March 2025).

Design problem and status of the guidance

Wind-driven rain is a natural consequence of combining strong wind flow with rain, particularly in naturally ventilated high-rise common spaces. BCA's guide identifies possible impacts including corridor ponding, inadequate drainage, slippery floors, seepage into lift shafts and units, deterioration of entrance-door materials and malfunctioning locksets. The guide's recommendations seek to minimise rather than eliminate those effects and must be calibrated to each site's conditions, project requirements, safety, security, sustainability and applicable regulations; they are good-practice guidance, not a guarantee of a dry building and not a statutory replacement for applicable requirements (BCA guide Version 1.0, accessed 2 September 2026).

Acceptance criteria and related requirements

The guide proposes wet-weather acceptance criteria for different spaces. Common areas such as sky gardens may experience splashing; corridors may have some splashing provided water flows toward an outlet; lift entrances should have no direct splashing; unit entrances should have no direct splashing, some wetness and no ponding; living spaces should have no wetness; and balconies may have some splashing as semi-outdoor spaces (BCA guide Version 1.0, accessed 2 September 2026). The same guide records accessibility requirements relevant to residential common corridors, including at least 1,500 mm clear width for an accessible route, no more than 50 mm level difference at the unit entrance and at least 300 mm manoeuvring space beside the leading edge of the entrance door.

Natural ventilation, fire safety and accessibility remain concurrent design considerations. The guide records Building Control Regulations parameters for natural ventilation, including openings with an aggregate area of at least 5% of the space to be ventilated and no part of the naturally ventilated space more than 12 m from an opening; project teams must still apply the relevant current regulations and competent-authority requirements (BCA guide Version 1.0, accessed 2 September 2026).

Site, form and passive design strategies

Designers are encouraged to assess site conditions early, including adjacent open spaces, water bodies and low-lying surrounding developments that may be associated with higher wind velocity around a high-rise development. Building form and the arrangement of naturally ventilated corridors can create wind-tunnel effects; openings facing oncoming wind may allow rainwater to penetrate deeper along a corridor (BCA guide Version 1.0, accessed 2 September 2026). Possible passive responses include parapet walls, vertical louvres or fins, horizontal overhangs, perforated screens, suitable entrance and lift-lobby detailing, and drainage design. The right combination depends on the site's wind, rain, ventilation, fire-safety and usability requirements.

Simulations, tests and maintenance boundary

The handbook includes wind-driven-rain simulation and the CONQUAS Water Flow Test as separate tools in its simulations-and-tests section. BCA encourages developers and designers to consider simulations during the early design phase so that targeted mitigation can be incorporated before downstream changes become difficult or costly; on-site observations during construction may identify a need for additional measures (BCA guide Version 1.0, accessed 2 September 2026). The guide also recognises an ongoing role for homeowners and MCSTs in regular maintenance and housekeeping. Simulation or testing does not transfer all statutory or maintenance responsibility to BCA, and the guidance does not promise to fully remove wind-driven rain from high-rise living.