The primary purpose of the Building Regulations is to provide for the health, safety and welfare of people in and around buildings. The regulations apply to new buildings, extensions and alterations to existing buildings and to certain changes of use of existing buildings.
Once you have received Planning permission and before you start building there are forms that may need to be submitted to the Council. Depending on what the development is you may need to send in a Commencement Notice or a 7-Day notice, Fire Safety Certificate and Disability Access Certificate - Fire Service Forms & Downloads
Please note that from March 1st 2014 new Commencement Notice procedures apply. The Notice should be submitted online on the National Building Control Management System
More information and Legislation: https://www.gov.ie/en/publication/95d00-building-standards/