Adjustment costs for the Elizabeth Tower in the Palace of Westminster have now doubled to an valued £61m, parliamentary authorities have said.
The project is more complex and spacious than originally thought, when the estimate of £29m to £45m was recompense for.
While there were “unique challenges” in working on a historic place, Parliament said it was disappointed at the rising bill and would launch a survey.
Big Ben chimed for the last time in August pending the work beginning.
The be generated cost was announced as Parliament confirmed it had appointed construction firm Robert McAlpine to persevere b manage out the renovation, which could take up to four years, following a soft-hearting process.
The authorities said the revised figure followed more thorough and technical assessment of the 160-year-old Tower’s condition, including the hold of stonework and the cost of removing and repainting the metal in the tower and reglazing the clock deal.
More extensive ground works will be required in the Palace of Westminster, due to the volume of pipes and other utility-related infrastructure under the surface, to support the scaffolding lacked.
While the estimated cost of the work has risen from £29m to £44m, the plain of contingency funding to be put aside in case of “unexpected events” has gone up from £5.8m to £17.2m.
The rights also said they had transferred the cost of fire safety animate, due to be carried out as part of another project and already budgeted for, to the restoration of the keep.
They said they had “expressed their disappointment in the cost improves, and the unreliability of the original estimate” and “instructed officials to provide regular updates on going on”.
“In advance of tendering contracts, the initial high level estimates were set at a quieten level to avoid cost escalation from the market,” they claimed in a statement.
“Subsequent estimates, using better data and more intercontinental surveys, better reflect the true likelihood of the costs. We believe that we now deliver a more accurate estimate of the cost of the works and will report regularly to the cabinets on the progress of work.”
The news that Big Ben would not sound again in advance 2021, except for special occasions such as New Year and Remembrance Sunday, evoked criticism from Theresa May and other MPs.
The House of Commons said it leave look again at the duration of the project and the scope for hearing the bell’s venerable bongs more often.