The Seanad is to move to the National Museum from next September as part of the renovation and structural works, which will continue until the end of 2018.
Leinster House will be covered in scaffolding as the stone facade, windows, and roof are repaired, while much of the inside is also opened up and refurbished.
The Irish Examiner understands the project is likely to cost between €16m and €18m, but the OPW refused to provide even a ballpark figure for the total spend.
Ceann Comhairle Seán Ó Fearghaíl said: “What it is going to cost will depend on what is found.”
John Cahill of the OPW said they had been opening floors since 2007 but have yet to examine the whole building. “The actual repair is something that we don’t have a full figure on or a final figure on,” he said. “In terms of the money that is needed it is mainly skills-based, it is craftsmen, and that’s why the full estimation of the cost is not something we can make up at the moment.”
Asked if there is a total budget, Mr Cahill said: “We have to do the job. We have already said that in going out for tenders, that the construction cost, net of everything else, will be in the order of at least €8m because we have to indicate to Europe the scale of what’s there, but that’s only indicative of the type of figure that you are talking about.
“You are talking about all those skills, all that time for plaster restoration in the interior, all those elements in which we haven’t had a chance to lift the floors and get into, so that will add to the cost.”
The decision to move the Seanad to the National Museum sparked controversy when first announced.
Mr Ó Fearghaíl said: “Staff and board members, I think, would have felt with some justification that this was an attempt by the Oireachtas to smash and grab, that we were intent upon a campaign of getting access to the space which we would hold on to, and which would leave the National Museum severely disadvantaged.”
However, he said a memorandum of understanding has been signed promising that the Seanad move will be a temporary relocation.