Permission for housing in Flood Zone A is difficult to obtain, because the national guidelines treat residential development as highly vulnerable and direct it away from high probability flood areas. It is possible only where the Justification Test is satisfied and a detailed site-specific flood risk assessment shows risk can be managed.
The starting position in the guidelines is avoidance: highly vulnerable development should not be located in Zone A. Where a planning authority is considering such a proposal, it must apply the Justification Test, which requires among other things that the development is on land zoned or otherwise designated for that use in the development plan and that it is essential to the wider planning objectives for the area.
A one-off house on an unzoned Zone A site will rarely meet those requirements. Where a proposal does proceed, a detailed flood risk assessment, design measures such as raised floor levels, safe access and flood-resilient construction, and confirmation that flood risk is not increased elsewhere will all be scrutinised.