Crumbling Huddersfield Royal Infirmary has “concrete cancer”, is in danger of collapse without repairs, and would have to be demolished in 10 years, engineers have said.

Technical details of the problems with the 52-year-old infirmary have emerged in the Full Business Case (FBC) for the controversial hospital shake-up, which was published on Friday.

Hospital chiefs are hoping to tear the 1960s built Lindley site down and move most care to Halifax.

They say a £95m backlog in maintenance is required to keep it operational over the next 10 years.

But it has emerged that property management firm Lendlease, which operates the Calderdale Royal Hospital site, has advised that HRI is “time expired” and would have to be knocked down anyway, whether the shake-up plan is given the green light or not.

They have said even if the £95m was spent, the building would not meet NHS standards in 10 years’ time.

Structural engineers have warned it is at risk of collapse if any more holes are drilled in the floors.

Replacing HRI is estimated to cost £380m – £83m more than the proposed plan to extend CRH and Acre Mills.

The FBC says “there is a high risk of failure of critical services such as power supply, heating, hot and cold water services and medical gas services.”

But the ban on drilling holes means no pipes can be upgraded.

Structural engineers also say water seeping in behind stone facades has caused “concrete cancer”, causing it to crumble away.

Issues with asbestos, which the trust has already spent tens of thousands on, are still present, and nearly all the windows need replacing.

Leaking roofs, inadequate power supplies and sub-substandard fire safety systems also add to the estates headache.

If given the go-ahead, a timeline for the project shows construction to extend CRH could start as soon as the spring of 2019 with the whole scheme completed by the spring of 2022.

The FBC also reveals the new PFI deal would not be as bad value for money or as restrictive as the one used to build CRH – said to be costing taxpayers £22m a year in mortgage payments, more than £770m by 2058.

It says rules over contracts to run facilities management have been relaxed and shortened, allowing more competitive deals for areas such as cleaning, laundry and catering.

Meanwhile, the FBC has also revealed that parents would be discouraged from attending the proposed Urgent Care Centre at Acre Mills for injuries or emergencies for children under five-years-old.

Babies, tots and toddlers that do arrive at the Huddersfield site would be assessed, stabilised and then transported to the specialist children’s emergency department at Calderdale Royal.

In a third development, the FBC reveals that midwife led maternity services would be retained in Huddersfield at the Acre Mills site.