This data is collected through the BCMS, Building Control Management System, which is operated by the LGMA. It is collated and issued to the DECLG 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 single residential units commenced - the total number of one off residential units which are associated with the commencement notices submitted for that month. This figure is included within the total number of residential units commenced.

Differences to the previously collected between 2004 and early 2014:
Methodological difference: The previous data was collated from 37 Building Control Areas by the DECLG. 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.

Carlow data Mar 2016; Adjusted downwards from 4 due to revised data Cork city data 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 Jun 2015; Data adjusted in Jan 2016 from 37 to 36 on foot of revised data from BCMS due to retrospective submission Donegal data May 2015; Data adjusted in Dec 2015 from 20 to 19 on foot of revised data from BCMS due to retrospective submission Donegal data Jun 2015; Data adjusted in Jan 2016 from 22 to 21 on foot of revised data from BCMS due to retrospective submission Donegal data Mar 2016; Adjusted upwards from 14 due to revised data Fingal data Sept 2015; Data adjusted in Dec 2015 from 3 to 4 on foot of revised data from BCMS due to retrospective submission Galway county data Apr 2015; Data adjusted in Dec 2015 from 21 to 22 on foot of revised data from BCMS due to retrospective submission Louth data Mar 2016; Adjusted upwards from 10 due to revised data Monaghan data Aug 2015; Data adjusted in Feb 2015 from 7 to 6 on foot of revised data from BCMS Monaghan data Mar 2016; Adjusted downwards from 13 due to revised data Roscommon data Feb 2016; Adjusted upwards from 2 due to revised data Tipperary data Sept 2015; Data adjusted in Dec 2015 from 7 to 8 on foot of revised data from BCMS due to retrospective submission Tipperary data Oct 2015; Data adjusted in Dec 2015 from 10 to 11 on foot of revised data from BCMS due to retrospective submission Westmeath data Sept 2015; Data adjusted in Dec 2015 from 6 to 7 on foot of revised data from BCMS due to retrospective submission Wicklow data Sept 2015; Data adjusted in Dec 2015 from 11 to 12 on foot of revised data from BCMS due to retrospective submission