The cost of repairing “one of the most important buildings in Surrey” has ballooned to nearly £2 million after further setbacks were discovered – with Waverley Borough Council now on the hook for about three quarters of a million pounds.

The Grade 1 listed Farnham Museum has been protected due to the exceptional interest in its rare design. Its listing places it alongside some of the nation’s most famous landmarks including Buckingham Palace, Hampton Court and the Cenotaph.

In March 2023, funding for the project was secured after the Arts Council gave Waverley Borough Council a grant of £734,335 for essential repairs to its Wilmer House, Georgian home, in West Street.

The council-owned building had fallen into disrepair with the cash used to address decaying brickwork, its collapsing second floor window arches, and deeply eroded mortar joints.

Further exploratory work uncovered a wrath on additional problems with the budget growing ever since. Senior councillors has described the work as vital to protecting the “extremely valuable building” and that describing its worth in monetary terms “felt a little grubby”.

Following the Tuesday, June 3, meeting of Waverley Borough Council, which agreed to set aside an additional £243,000 for the project, the total cost is expected to be £1,720,000 – of which £735,000 will be funded by the council.

Councillor Kika Mirylees, portfolio holder for community services and leisure said: “Wilmer House is a grade one listed building and is extremely rare being one of fewer than 20 buildings of its type.

“As a Grade-1 listed building it sits alongside other somewhat more famous buildings such as Buckingham Palace, Hampton Court, the Tower of London and the Cenotaph. However, as we know, the challenges that come with a Grade 1 listed building are not easy.”

She added: “The first phase was always going to be one of uncertainty, we knew that, until the scaffolding came down and we saw what was lying behind it. The extra funding we need will be for the parapet wall and the two chimneys, which will make up the majority of the extra funding because we can not leave them as they are.

“Their deterioration is much greater than expected and they were not part of the tendered contract. “Like it or not Waverley has a statutory obligation to carry out the repair work in a timely manner due to planning law and health and safety concerns – and the funding given to us by the Arts Council.”

It is expected that the work will take about 18 weeks to complete and will be finished by mid October, the meeting heard. Any delay would have a knock on effect and push the project into the next year, resulting in a third consecutive winter shut down and costing a further £69,000.

Cllr Mark Merryweather, portfolio holder for finance, assets and property added: “When you go up there and have an expert explain to you the history of the building, the skill that went into the original works there, it almost feels slightly grubby to start monetising it, because it is an extremely valuable building.

“But having said that we have to, we are a council, we have a responsibility – not only to our taxpayers, but to Farnham and the borough, and to the nation because this is a nationally important building.

“In our stewardship and custody I am confidant its going to be looked after the way it should. Its disappointing we’ve found more work that needs to be doing but no one can say we weren’t fully aware of the risk.”