The £5m restoration work on Kilmarnock’s historic Dean Castle has stalled after the main contractor went out of business.
CBC Stone went into administration during lockdown, according to an East Ayrshire Council report.
Now council bosses will seek to hire a new firm to take on the mammoth project.
Officials are not yet sure when work will restart.
East Ayrshire Council leader Douglas Reid said: “We are trying our best to get another contractor to step in. It is a big attraction to the area and brings footfall to the visitor centre.
“We are anxious that the work is done as soon as possible and done right.”
Water getting in to the keep was one of the problems which sparked the ongoing refurbishment project.
The 14th century landmark’s precious museum collections had to be moved to the Dick Institute to keep them safe before the makeover began.
Plans include a recreated medieval kitchen in the cellar and a raised floor to make it accessible to all visitors.
Finance for the project came from the Heritage Lottery Fund, Historic Environment Scotland and East Ayrshire Council.
By Local Democracy Reporter Sarah Hilley