Is my house in a flood zone? How to check
- Check every layer, not just one. Open the OPW flood maps on floodinfo.ie, find the site, and switch on river, coastal and surface water flooding in turn, at each likelihood. Or search the address on InSite above, which checks all 21 layers across the whole plot at once.
- Work out the flood zone. Inside the 1% river or 0.5% coastal extent is Flood Zone A; inside the 0.1% extent is Flood Zone B; outside both is Flood Zone C (see below).
- Look at the future scenarios. A site that's just outside today's extent may be inside the mid-range or high-end climate extent.
- Check past floods. floodinfo.ie also records past flood events. Ask neighbours and the council too.
- If the maps are blank, check whether the area was assessed. Blank can mean "not mapped" rather than "safe" (see the limits below).
What the flood maps show
The maps come from the OPW's Catchment Flood Risk Assessment and Management (CFRAM) programme and are published at floodinfo.ie. They cover three kinds of flooding:
- River (fluvial): rivers overtopping their banks.
- Coastal: high tides and storm surges.
- Surface water (pluvial): heavy rain that can't drain away fast enough, mapped for today's climate only.
River and coastal flooding are also mapped under a mid-range and a high-end future climate scenario. Flood extents usually grow, sometimes onto land that's dry on today's maps.
What the 10%, 1% and 0.1% bands mean
Each extent is labelled with its annual exceedance probability (AEP): the chance of a flood at least that big in any one year.
| Band | River | Coast | Roughly |
|---|---|---|---|
| High probability | 10% AEP | 10% AEP | about a 1-in-10 chance each year |
| Medium probability | 1% AEP | 0.5% AEP | 1-in-100 (river) or 1-in-200 (coast) each year |
| Low probability | 0.1% AEP | 0.1% AEP | about a 1-in-1,000 chance each year |
A "1-in-100-year flood" is not a flood that happens once a century. It's a 1% chance every year, and two can happen in consecutive years. Over a 30-year mortgage, a 1% yearly chance adds up to roughly a 26% chance of at least one such flood.
How planning uses this: Flood Zones A, B and C
Councils assess planning applications against The Planning System and Flood Risk Management: Guidelines for Planning Authorities (2009), which sorts land into three zones:
- Flood Zone A (high probability): inside the 1% river extent or the 0.5% coastal extent.
- Flood Zone B (moderate probability): between those and the 0.1% extent.
- Flood Zone C (low probability): outside the 0.1% extent.
The guidelines steer "highly vulnerable" development, which includes homes, towards Zone C. Development in Zones A or B generally has to pass a "Justification Test", and the council will usually ask for a site-specific flood risk assessment prepared by an engineer.
What the maps can't tell you
- Areas that weren't assessed in detail. The detailed maps cover specific river and coastal areas. Elsewhere, a blank map means "not assessed", not "won't flood".
- Groundwater flooding. Flooding from rising groundwater, common in some limestone areas, is mapped separately by Geological Survey Ireland (its historic groundwater flood map).
- Local drainage. Blocked culverts, a badly drained field or a low spot in a driveway won't show on a national map.
- Flood history. These are predictions. floodinfo.ie also records past flood events, and neighbours often know more than any map.
- Insurance. Insurers use their own models, which may not agree with the OPW maps.
Common questions
Is floodinfo.ie the official flood map?
Yes. It's the OPW's own site for the national flood maps from the CFRAM programme, plus records of past flood events. InSite reads the same maps.
What is Flood Zone A?
Land with a high probability of flooding: inside the 1% (1-in-100) river flood extent or the 0.5% (1-in-200) coastal extent. Councils generally won't permit new homes there unless the development passes the Justification Test.
Can I get planning permission in a flood zone?
Sometimes, in Zone B or where the development plan has already justified the zoning, but expect to need a site-specific flood risk assessment and design measures such as raised floor levels. In Zone A, a new house is rarely permitted.
Sources
- OPW flood maps (CFRAM): floodinfo.ie
- The Planning System and Flood Risk Management: Guidelines for Planning Authorities (2009), Department of the Environment, Heritage and Local Government and the OPW
- Geological Survey Ireland, historic groundwater flood map
Last reviewed 2026-10-22.