Can I build a house in a flood zone in Ireland?

The Planning System and Flood Risk Management Guidelines for Planning Authorities, issued jointly by the Department of Housing, Local Government and Heritage and the OPW, set out a risk-based framework that planning authorities must apply when assessing development in areas at risk of flooding. Land is classified into Flood Zone A (highest probability of flooding), Flood Zone B (moderate probability) and Flood Zone C (low probability), and new residential development — classified as a highly vulnerable use — is generally directed towards Flood Zone C.

A house proposed in Flood Zone A or B is not automatically refused, but it must pass the 'sequential approach' (showing no reasonably available lower-risk alternative site exists) and, where an exception applies, the 'justification test' set out in the guidelines, which requires demonstrating a compelling need for the development in that location that outweighs the flood risk. Even where the tests are passed, planning conditions requiring flood-resilient design, raised floor levels or mitigation measures are common.

Development plans typically include strategic flood risk assessments that map flood zones for the functional area, and site-specific flood risk assessments are usually required for individual planning applications in or near a mapped flood zone, assessing not just river or coastal flooding but also pluvial (surface water) and groundwater flooding risk.