Limerick City and County Council is upgrading its offices at county hall in Dooradoyle and at Merchant's Quay in Limerick to improve the energy performance and fire protection of both buildings.
But specific works at to take place at the Merchants' Quay building after tests revealed the presence of pyrite.
In a statement the council said: "Specifically in relation to the Merchant's Quay building, Limerick based structural engineers have been monitoring the building facade for some time.
"These reviews have taken cognizance of recent test results of the walls and floors of the building which indicate the presence of pyrite in a few locations.
"The structure is being monitored both internally and externally and to-date has not seen deterioration that would cause concern.
"The external plasterwork has generally been in very good condition which has protected the outer block walls very well over its lifetime.
"To ensure the building continues to be safe to use, the Council have put in place a regime of regular inspections and monitoring procedures, following the expert advice of our engineers, to report any deterioration of concern to ensure repairs or protective measures are arranged promptly."
The works to be undertaken at both buildings include improving the energy performance, providing more bicycles spaces and EV charging points, upgrading the fire protection and ventilation systems, as well as upgrading kitchen and bathroom facilities.
The offices will remain open to the public with as little disruption to the public as possible.