As you will be aware, Ireland is at level 5 of the Government's Strategy, Resilience and Recovery 2020-2021: Plan for Living with COVID-19 . This 5-level framework sets out what is permitted for social or family gatherings, work and public transport, bars, hotels and restaurants, exercise activities and religious services, at that moment in time.
The various limits at all levels in the Government's Plan and the continuing imposition of public health measures is necessary to reduce transmission of COVID-19 through a reduction in the movement of people, congregation and interactions. The measures in place for each level reflect the prevailing disease situation and recognise that we can and must prioritise some activities over others.
Information in relation to the public health measures for construction at level 5 is available at:-https://www.gov.ie/en/publication/2dc71-level-5/#construction
I would also draw your attention to the Health Act 1947 (Section 31A - Temporary Restrictions) (COVID-19) (NO. 10) Regulations 2020 Regulation (S.I. 701 of 2020), as amended by S.I. No. 4 of 2021, which sets out what are essential construction and developments.
Statutory Instruments related to the Covid-19 pandemic are available here:-https://www.gov.ie/en/collection/1f150-view-statutory-instruments-related-to-the-covid-19-pandemic/
At the start of January, transmission levels were at exceptionally high levels and this required the application of very severe restrictions to reduce opportunities for transmission as much as possible, which included the shutdown of the construction sector.
You may wish to note that my Department does not have responsibility for the construction sector. The shutdown of the construction sector (including the construction and developments permitted to continue), was confirmed by the Minister for Housing, Local Government and Heritage by press release on the 6 January, 2021. Further information on these projects is available here:-https://www.gov.ie/en/press-release/53a69-minister-obrien-confirms-shutdown-in-construction-activity/