This data is collected through the BCMS, Building Control Management System, which is operated by the LGMA. It is collated and issued to the DHLHG on a monthly basis. Each commencement notice details new residential units which will be constructed in that month.
Due to the nature of the commencement notice process, there may be slight changes to previously published data due to retrospective processing of notices.
Up until August 2015, Local Authorities or builders carrying out work on behalf of a local authority were not required to submit Commencement Notices provided that the work in being carried out in that local authority's administrative area. After 1/9/2015, Local Authority units are included in the commencement notice data.
The Dublin local authorities area includes Dun Laoghaire, Fingal, South Dublin and Dublin City. The Greater Dublin Area includes all four Dublin local authorities and Kildare, Meath and Wicklow.
Definition of the variables above:
Number of residential units commenced - the total number of residential units which are associated with the valid commencement notices reported on for that month. One off units are included within this figure.
Differences to the previously collected between 2004 and early 2014:
Methodological difference: The previous data was collated from 37 Building Control Areas by the DHLHG. This data is drawn from a database of information held by the LGMA from data directly inputted by developers/builders online or by the local authority.
Definition difference: The 2004-early 2014 data used the date of receipt of the commencement notice i.e. a notice received in March could relate to a project commencing in April yet would be reported in the March dataset. This dataset from the BCMS uses the date of commencement of the project i.e. a notice received in February with a commencement date of March will be reported in the March dataset. The most current data is published on these sheets. Previously published data may be subject to revision. Any change from the originally published data will be highlighted by a comment on the cell in question. These comments will be maintained for at least a year after the date of the value change.

Clare data for May 2016; Adjusted upwards from 12 on basis of revised data Cork city data for Feb 2015; Data adjusted in Dec 2015 from 0 to 1 on foot of revised data from BCMS due to retrospective submission Cork county data for Jun 2015; Data adjusted in Jan 2016 from 73 to 72 on foot of revised data from BCMS due to retrospective submission Donegal data for May 2015; Data adjusted in Dec 2015 from 20 to 19 on foot of revised data from BCMS due to retrospective submission Donegal data for Jun 2015; Data adjusted in Jan 2016 from 22 to 21 on foot of revised data from BCMS due to retrospective submission Donegal data for Mar 2016; Revised upwards from 13 due to revised data Fingal data for Sept 2015; Data adjusted in Dec 2015 from 105 to 106 on foot of revised data from BCMS due to retrospective submission Galway county data for Apr 2015; Data adjusted in Dec 2015 from 21 to 22 on foot of revised data from BCMS due to retrospective submission Kildare data for Jun 2016; Adjusted upwards from 194 on basis of revised data Louth data for Mar 2016; Adjusted upwards from 20 due to revised data Meath data for May 2016; Adjusted downwards from 76 on basis of revised data Monaghan data for Jul 2016; Revised downwards from 102 Tipperary data for Sept 2015; Data adjusted in Dec 2015 from 7 to 8 on foot of revised data from BCMS due to retrospective submission Tipperary data for Oct 2015; Data adjusted in Dec 2015 from 10 to 11 on foot of revised data from BCMS due to retrospective submission Tipperary data for Feb 2016; Adjusted upwards from 12 due to revised data Westmeath data for Sept 2015; Data adjusted in Dec 2015 from 6 to 7 on foot of revised data from BCMS due to retrospective submission Wexford data for Feb 2016; Adjusted downards from 16 on basis of revised data Wicklow data for Feb 2015; Data adjusted in Dec 2015 from 89 to 90 on foot of revised data from BCMS due to retrospective submission