Residential Commencement Notices Background and Methodology

This page explains how we collect and check data on new building projects in Ireland to ensure our housing statistics are accurate.

A Commencement Notice is a formal notification sent to a local council (Building Control Authority) to signal that a person intends to start building work or significantly change how a building is used.

• When to notify: You must submit the notice between 14 and 28 days before work begins.
• Deadline to start: Once the council accepts the notice, work must start on-site within 28 days.
• Large projects: For big developments, builders usually submit a separate notice for each phase of the project, listing the number of homes in that specific stage.
• How to submit: All notices are submitted online through the Building Control Management System (BCMS), which is managed by the Local Government Management Agency.

The Department of Housing downloads data from the BCMS to track housing supply. To make sure the final numbers reflect actual construction activity, we follow these steps:

1. Filtering: We remove non-residential buildings, duplicates, and small projects like home extensions or garages.
2. Validation: We compare the number of units listed in each notice against the project descriptions and other records to fix any mistakes.
3. Updates: Because new information can arrive at different times, we occasionally make small updates to previously published figures.
4. Local Boundaries: Our reports account for the boundary changes between Cork City and Cork County that took effect on 31 May 2019. All data from June 2019 onwards uses these new boundaries.