Some cases could be held at alternative sites for essential repairs to be carried out at a Caernarfon’s court building.
The upgrade taking place this summer will see improvements to the roof and air system at the Caernarfon Justice Centre.
The centre on Llanberis Road will remain open throughout the work, but three courtrooms will close temporarily.
A Ministry of Justice statement said the refurbishment will replace the building’s air handling unit which feeds two Crown courts and to improve long-standing heating and cooling issues.
The scope of the project was also extended to replace an area of the roof because of water ingress in the Crown courts.
The project started on Friday, 12 July, and is expected to last for nine weeks.
Any disruptive work has been scheduled to take place on weekends or outside of core court hours.
Cases, where necessary, will be moved to different locations until the project is completed.
A spokesperson for His Majesty’s Court and Tribunal Services said: “Caernarfon Justice Centre will undergo essential works this summer including upgrading the court’s air system and repairs to its roof.
“We’ve put plans in place to minimise the disruption this may cause and impacted cases will be heard at neighbouring sites.”