Flood resilient construction uses methods and materials that reduce the impact from a flood, ensuring that structural integrity is maintained, and the drying out and cleaning required, following inundation and before reoccupation, is minimised.
Concrete is inherently water resilient and entirely suitable in a construction designed to be either waterproof, as required for water barriers, or water resilient. Its use in the construction of basements, swimming pools and water storage tanks demonstrates concrete's performance in this regard. The extent to which the structure keeps out moisture depends on the specification of the concrete itself and its design details, corner junctions for example.
Categorisation of the flood resilient properties of various construction materials and guidance on appropriate flood management strategies is provided in the British Standard BS 85500:2015 Flood resistant and resilient construction – Guide to improving the flood performance of buildings.
A 2016 Action Plan sets out how businesses can make it easier for people to protect their homes from damage from flood water.
A water exclusion strategy, or resistance strategy, for low depth flooding, is designed to prevent flood water entering the building and minimise the impact of flood waters and to give occupants more time to relocate ground floor contents.
A water entry strategy, or resilience strategy, for greater flood depths includes measures incorporated into the building to reduce the impact of flood water on the property once water has entered.
Insitu and precast concrete have low permeability so resulting in minimal damage or deformation from a flood. They are appropriate for use in buildings that require either a water exclusion strategy or a water entry system, where other construction techniques could incur structural damage due to excessive differential pressures.
Summary of water exclusion strategy construction details:
- Concrete foundations: provide a barrier to water entry into the wall cavity.
- Floors: ground supported concrete slabs of min. 100mm thick can prevent loss of structural integrity due to uplift pressures due to water ingress from the ground.
- Walls: clear cavity or solid masonry walls offer better flood resilience than filled or part-filled cavity walls.
Summary of water entry strategy construction details:
- Floors: as for the water exclusion strategy
- Walls: as for the water exclusion strategy. Note: to meet current standards high density internal insulation can be used.