The Scottish Parliament could reach the end of its “useful life” by 2060.
Architectural experts warn MSPs will have to approve a massive refit bill or face moving to a new building.
Speaking to a Sunday newspaper, architectural writer David Black said, “It doesn’t compare terribly well with the Scottish Parliament Hall in Edinburgh, which was built in 1639 and is still there.
“The Holyrood building has in-built problems. It is so ridiculously over-engineered.”
Peter Wilson, who was project architect for the Museum of Scotland, said: “The Scottish Parliament should have cost about £150 million if it had been managed properly. But it was totally mismanaged, though an inquiry, which was a whitewash, said no one was to blame.
“But you could say the building has more value than some of the occupants. If you replaced them with wall or loft installation, you wouldn’t know the difference.” A Scottish Parliament spokesman added: “Our annual accounts assume an initial 50-year depreciation period for the building, which is based on standard practice.”