Flood maps when buying a house — what floodinfo.ie shows, flood zones A, B and C, and why we only flag

We hold 27,460 flood-extent features from the OPW's CFRAM mapping for the four Dublin councils, and in the 12 months to 12 September 2026 just 36 of the applications the seven Greater Dublin councils decided mentioned flood risk in their description. One was refused. That gap — a great deal of mapped floodplain, very few applications that say so — is why a buyer has to check the map, because the register alone will not tell you.

What floodinfo.ie shows

The Office of Public Works publishes the national flood maps at floodinfo.ie. Three layers matter. The CFRAM maps, from the Catchment Flood Risk Assessment and Management programme completed in 2018, show modelled flood extents for 300 communities — river and coastal — at three probabilities: the 1 in 10, 1 in 100 and 1 in 1,000 year events, with climate-change scenarios beside them. The National Indicative Fluvial Maps cover rivers outside the CFRAM areas at coarser precision. The past flood events layer records where flooding has been reported, with the year and the source.

A house inside a CFRAM 1 in 100 extent is not a house that floods every century. It is a house the model puts inside the area with a 1% chance of flooding in any year, before defences are counted where the map is the undefended one. Read the legend: the maps for a defended community show both the defended and the undefended case, and Clontarf, Sandymount and the Dodder corridor read very differently between the two.

Flood zones A, B and C

The 2009 Guidelines, issued under section 28 of the Planning and Development Act 2000, turn those probabilities into planning rules. Flood Zone A is the area with a river flood probability of 1 in 100 or more, or coastal 1 in 200. Zone B runs out to 1 in 1,000. Zone C is everywhere else. Each development plan carries a Strategic Flood Risk Assessment that draws the zones, and each council must have regard to the Guidelines when it decides an application.

The rule is sequential: avoid, then substitute, then justify. Housing is a "highly vulnerable" use, so a new house in Zone A or B needs the Justification Test — a demonstration that the site is in a settlement the plan wants to grow, that there is no alternative, and that the design manages the residual risk. An extension to an existing house in Zone A is treated more lightly, but the council will ask for finished floor levels and a flood risk assessment on any site the SFRA marks.

Why we flag rather than draw

The address report says whether a pin falls inside a mapped flood extent and which layer it came from. It does not reproduce the map. The OPW's data is published under a licence that permits viewing and internal use but not republication of the extents, so the map itself is the OPW's to show; the flag sends you to floodinfo.ie with the location filled in. Our reading: the flag is enough to decide whether to spend an hour on the OPW site, and no more than that.

The flag is also silent on three things the OPW map is silent on. Pluvial flooding — rain that cannot drain — is not mapped nationally, and it is the most common cause of a flooded Dublin basement. Groundwater is mapped only in the west. And a completed defence scheme changes the insurance position without changing the undefended extent, which is the one most people read first.

Insurance and the vendor

Since the 2014 memorandum of understanding between the OPW and Insurance Ireland, insurers receive the OPW's data on completed defence schemes and are expected to take it into account. They are not obliged to offer cover. Ask the vendor two questions before you go sale agreed: has the property flooded, and is it currently insured for flood at a standard premium. A vendor's silence on a past flood is a matter for the pre-contract enquiries and your solicitor, and the past-events layer on floodinfo.ie is where you check the answer.

If the council granted a permission for the house or its extension with a flood risk assessment attached, the assessment is on the council's file and is the best account of the site you will find. The Explorer lists the application; the file is one click further.

Frequently asked questions

How do I check if a house is at risk of flooding in Ireland?

Search the address on the OPW's floodinfo.ie and read the CFRAM or NIFM extent, the probability, and whether the map is the defended or undefended case; then check the past flood events layer. Our address report flags whether the pin sits inside a mapped extent.

What is flood zone A?

Under the 2009 Planning Guidelines, the land with a 1 in 100 or greater annual probability of river flooding, or 1 in 200 coastal. New housing there must pass the Justification Test; an extension to an existing house is assessed on its floor levels and a site-specific flood risk assessment.

Will a house on the flood map be uninsurable?

Not automatically. Insurers use the OPW data on completed defences under the 2014 memorandum, and a property behind a finished scheme is usually insurable. A property inside an undefended extent with a recorded past flood is where cover gets expensive or refused. Ask the vendor for the current policy.

Does a planning search show flood risk?

No. The law searcher's report returns the planning register; flood risk appears only where an application's description or a condition mentions it. Thirty-six decided applications in the Greater Dublin Area did so in the last year.

The sale-agreed checklist puts the flood check beside the planning search and the RZLT map; the planning search guide explains what the register search covers. Open the Explorer on the Dodder at Rathfarnham, one of the CFRAM communities, or the South Dublin County Council place page.

Figures from the register on 12 September 2026 (live callouts refresh hourly); law checked 12 September 2026. Check with the council or a planning consultant before relying on this.