Repair work has begun at Yeovil District Hospital after a rooftop platform holding machinery started to move.

The project – which could last up to nine months – will relocate the steel platform supporting ventilation systems for the hospital’s £3.1 million sterile services unit.

The platform started to shift when a support became dislodged last March.

It is now being moved several metres away from its original location and will sit on top of the accident and emergency department.

Temporary work to stabilise the failing structure resulted in part of the hospital’s day theatre – two storeys below – being closed since last April, but the hospital has stressed that patient care was not affected.

Director of estates and facilities, Robert Steele, said: “We can assure patients and visitors that health and safety is our priority at all times and there has not been, and will not be, any risk to anyone who uses the hospital while the work is carried out.

“The cost of rectifying the issue, which has had no impact on patient care, is being paid for by the contractors and we are satisfied with the way they are dealing with it.”

However, documents submitted to South Somerset District Council’s planning department by the hospital’s construction contractor cfes suggested the disruption had been more significant.

“Due to unforeseen factors, elements of the structure supporting the external plant platform dislodged, causing the platform to shift,” the document said.

Stabilisation work was carried out immediately to prevent further movement, the report added. A prop was installed through the roof of level three as a temporary solution, causing “considerable disruption to the day theatre and related areas.”

It said the measures were needed to “ensure health, safety and welfare of all people associated with the hospital... was not compromised or put at risk.”

The day theatre is used for operations where patients are not required to stay overnight.

A hospital spokeswoman said the operating theatre itself was unaffected, but a rarely-used cubicle where patients wait before surgery was put out of action.

The spokeswoman said: “We have plenty of capacity in day theatre cubicles so it has made no difference to patient care.

“No operations were delayed or postponed as a result.”

A permanent solution to secure the platform in its original position could not be found, the planning document said, as it required a connection to columns which were damaged by the platform’s movement.

“There was concern the performance of the existing structure could be compromised by further physical structural connections. It was stipulated by the (hospital) trust that the columns would be repaired but not used for structural support,” the report added.

Building new columns to support the platform was also rejected because it risked closing down the accident and emergency and related X-ray departments, as well as the day theatre during construction.

Planning permission to move the platform was granted last October and work began last month.

A screen will be built around the new platform which will be about 100 square metres.

Scaffolding has been put up between the accident and emergency department entrance and the main hospital entrance to allow workers to access the roof. Part of the footpath has been be moved to make way for the scaffolding. A crane will be used at several stages of the project.

The work is expected to be finished by August and will involve a partial closure of the sterile services department over the Easter weekend, when no elective operations are carried out at the hospital.

The hospital spokeswoman said patients should not be affected. She said: “We have contingency plans to obtain sterilised equipment from neighbouring hospitals in the event of an emergency or major incident.”

The sterile services unit opened in September 2010.

According to the hospital’s website, it decontaminates medical equipment for hospitals, GPs, dentists and podiatrists across the South West, as well as Yeovil District Hospital. It has automatic washing machines to clean equipment and an autoclave to sterilise instruments.