Information about attached garages below the Flood Assessment Certificate level

Introduction

A Flood Assessment Certificate (FAC) is required by the Selwyn District Plan to set a floor level for a building. This is to prevent likely known flood effects in a 1:200-year storm event.

If you propose to build a garage attached to a dwelling where the garage floor level is below the required finished floor level of a Food Assessment Certificate, your design will need  incorporate requirements to ensure safety, material durability, and general compliance with regulations.

This guidance outlines some key considerations for the owner and designer for mitigating flood effects and maintaining safety.

1. Building material durability

  • Flood-resistant materials

Building elements that will be below the recommended floor level must be constructed from durable, flood-resistant materials.

These materials should withstand water exposure without significant damage or degradation. This includes structural elements. Doors or floor finishes should also be suitably specified.

2. Electrical fittings and equipment

  • Elevated electrical installations

Electrical outlets, switches, and other fittings must be installed above the recommended FAC floor level height to minimise the risk of electrical hazards during flooding events.

  • Waterproof enclosures

Electrical appliances and controls must be located on raised plinths above the FAC floor level.

3. Flood water management and drainage

  • Drainage systems

Ensure effective drainage systems are in place to divert water away from the garage and prevent pooling inside.

  • Sump pumps

These may be considered in low-lying garages as part of the building design to remove water that may accumulate during heavy rainfall or flooding; with specific regard to the outfall location from the pump.

4. Insurance coverage considerations

  • Flood insurance

Homeowners should review their insurance coverage to ensure it includes protection against flood damage.

The durability requirements of the building code should ensure that the building remains undamaged, however, contents within the garage will need to be considered.

  • Building Act sections 71 – 74 natural hazards

A hazard notification may be placed on your record of title where the land is subject to a natural hazard (e.g. inundation). This may impact the ability to get insurance coverage and finance over the property.

Council must consider whether a natural hazard notice is appropriate in when a floor level of a building is set below the FAC. Designers will therefore need to consider features that demonstrate that the hazard has been mitigated, to avoid the notification requirements.

5. Resource consent considerations

  • Resource consent requirements

Any new attached garages built with floor levels lower than that required by the FAC require resource consent.

Council will assess potential risks to safety, property, and well-being as part of the application process.

6. Non-habitable space restriction

  • Design limitation on future conversions

Licensed building practitioners (LBP) should discuss with the property owner that the garage may not be able to be converted in the future from a non-habitable to a habitable space.

This is due to the reduced floor level and the inability to meet the performance requirements of the New Zealand building code (NZBC) and the rules of the district plan.

For more information on buildings in flood-prone areas, please contact our Duty Planner or visit our website for guidelines and application forms.