Flood Risk Maps in Ireland — How to Check opw.ie Before You Buy a Site
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opw.ie hosts floodinfo.ie, the national flood hazard mapping. Check it before you sign contracts on any site near a river or coast.
The Office of Public Works (OPW) hosts floodinfo.ie, the national flood hazard mapping for Ireland. Check it before you sign contracts on any site near a river or coast. The maps show Flood Zone A (1% annual exceedance probability, high risk), Zone B (0.1%, moderate risk), and Zone C (low risk). Sites in Zone A or Zone B require a Site-Specific Flood Risk Assessment (SSFRA), which a hydrologist or engineer prepares for €3,000–€8,000 as part of the planning application. The Planning System and Flood Risk Management Guidelines (OPW/DoEHLG 2009) govern the Justification Test for development in flood zones. A refused planning application on flood grounds is a deal-killer — the site can be redesignated but the process is slow and uncertain. Most Irish sites away from rivers and the coast are in Zone C; sites within 100 m of a river or tidal water need a check.
When this matters most
You're choosing a site near a river, coast, or known flood plain.
When this doesn't apply
Your site is on a hilltop in a designated settlement area.
Sources
OPW, National flood hazard mapping (floodinfo.ie). https://www.floodinfo.ie/
OPW/DoEHLG, Planning System and Flood Risk Management Guidelines 2009. https://www.gov.ie/
Frequently asked questions
How do I check flood risk on a site in Ireland?
Use floodinfo.ie, the national flood hazard mapping hosted by the Office of Public Works (OPW). Shows Flood Zones A (1% AEP), B (0.1% AEP), and C (low risk).
What is a Site-Specific Flood Risk Assessment?
An assessment prepared by a hydrologist or engineer for sites in Flood Zone A or B. Costs €3,000–€8,000. Part of the planning application. Justification Test may apply.
Can I build on a flood plain in Ireland?
In Zone A, generally no. In Zone B, only with a successful Justification Test. In Zone C, standard planning applies. Refused planning on flood grounds is a deal-killer.
When this matters most
You're choosing a site near a river, coast, or known flood plain.
When this doesn't apply
Your site is on a hilltop in a designated settlement area.
Where to go next
Next decision
The next step in your build sequence.
- Foul Drainage Connection in Ireland — Mains Sewer, Treatment System, or Septic →
- Is My Site Buildable in Ireland? The Five Checks That Decide It →
- Land Registry Check in Ireland — Folio, Map, and What to Look For Before You Buy →
- On-Site Electricity for a Self-Build in Ireland — Temporary Connection, Generator, or Solar →
- Ribbon Development in Ireland — The Planning Policy That Refuses Houses Along Rural Roads →
- Site Access in Ireland — Road Entrances, Sightlines, and the Road Opening Licence →
- Site Office and Welfare for a Self-Build — What You Need by Law (SHWW 2013) →
- Site Security on a Self-Build in Ireland — Hedges, Hoardings, CCTV, and Insurance →
- Site Survey in Ireland — Topographical, Measured, and Boundary Surveys →
Branch into
Adjacent decisions at the same stage.
- Percolation Tests in Ireland — EPA T-values, What They Mean, and What Costs When You Fail →
- Rural Housing Policy in Ireland 2026 — Local-Needs Tests and How Counties Vary →
- Septic Tank vs Mains Sewer in Ireland — When Each Applies and What It Costs →
- Well Yield Tests in Ireland — How to Confirm a Rural Water Supply Before You Buy →
Watch out for
Common mistakes, hidden costs, gotchas.
- Percolation Tests in Ireland — EPA T-values, What They Mean, and What Costs When You Fail →
- Septic Tank vs Mains Sewer in Ireland — When Each Applies and What It Costs →
- Site Assessment Cost in Ireland — Soil Test, Percolation Test, Water Test, and What to Order Together →
- Site Purchase Costs in Ireland — Stamp Duty, Legal Fees, and What Adds Up →
- Irish Soil Classification — Class 1 to Class 5+ and What Each One Costs You in Foundation →
Compare with
Alternative approaches worth knowing.