Skip to main content

Non-Unique Addresses (NUAs)

When working with Irish address data through the Eircode Address Database (ECAD) or Eircode Address File (ECAF), you will frequently encounter Non-Unique Addresses (NUAs). Understanding how to correctly identify and handle these is essential for accurate address capture, validation, and delivery routing.

What is a Non-Unique Address (NUA)?​

  • A Non-Unique Address (NUA) is an address that does not contain a unique building number or a unique building name.
  • Ireland has a very high level of non-unique addresses.
  • Approximately 35% of all Irish addresses are non-unique, which equates to 600,000 addresses nationwide.
  • The typical example of NUA addressing occurs in rural areas where every address in a townland is the same.
  • Because these addresses are identical, mail is delivered by the local knowledge of postal delivery personnel who know which addressee lives in which house.

What Makes NUAs Unique?​

  • For a NUA address, it is impossible to match to a unique record in the ECAD and assign an Eircode based on the text address alone.
  • Knowing the text address is simply not sufficient information to determine the Eircode.
  • For example, four separate houses in a townland can have the exact same address lines but each will have a completely different Eircode.
  • The API response includes a nua boolean field: true when the address is non-unique, false when it is unique.

Example API Response​

The following is an ECAD response for a rural NUA property. Note the empty building_name, building_number, and primary_thoroughfare fields — this address has no distinguishing text elements. The nua: true flag confirms it shares its address lines with other properties in the townland.

{
  "id": "ecad_1234567890|en",
  "dataset": "ecad",
  "ecad_id": "1234567890",
  "language": "en",
  "department": "",
  "organisation": "",
  "sub_building_name": "",
  "building_name": "",
  "building_number": "",
  "building_group": "",
  "primary_thoroughfare": "",
  "secondary_thoroughfare": "",
  "primary_locality": "Example Townland",
  "secondary_locality": "Nearby Village",
  "tertiary_locality": "County Name",
  "post_county": "County Name",
  "eircode": "A00 B1C2",
  "line_1": "Example Townland",
  "line_2": "Nearby Village",
  "line_3": "County Name",
  "line_4": "A00 B1C2",
  "nua": true,
  "address_type": "Residential Address Point",
  "building_address_type": "Single Occupancy Residential Building",
  "primary_locality_address_type": "Rural Locality",
  "secondary_locality_address_type": "Rural Locality",
  "building_type": "Detached",
  "building_use": "R",
  "longitude": -7.123456,
  "latitude": 53.123456,
  "country": "Ireland",
  "country_iso": "IRL",
  "country_iso_2": "IE"
}

Key fields to note:

  • nua — true indicates this is a non-unique address
  • eircode — the only reliable way to distinguish this property from its neighbours
  • longitude / latitude — precise coordinates for delivery routing
  • address_point_id / ecad_id — stable identifiers for the specific property

Best Practices for Handling NUAs​

1. Make the Eircode the Primary Identifier​

  • Traditional text deduplication will fail for 35% of Irish addresses. Use the Eircode (or ECAD identifiers like ecad_id or address_reference) to uniquely identify the property.
  • Never rely on line_1 through line_3 as unique database constraints for Irish addresses.

2. Guide the User Experience​

  • A search for an NUA townland will return multiple identical address strings.
  • Your UI should prompt the user to provide their Eircode to distinguish their specific property from their neighbours.

3. Verification Logic​

  • If nua is true: The text address lines are shared. The Eircode is strictly required to differentiate this specific property.
  • If nua is false: The text address lines (e.g., building number and street) are sufficient to uniquely identify the property.

4. Use Geographic Coordinates for Routing​

  • Because NUAs lack street names or building numbers, delivery routing by text alone is practically impossible without local knowledge.
  • Each ECAD address includes longitude and latitude coordinates, allowing you to pinpoint the exact building for delivery or mapping purposes.