AN appeal has been launched to raise £500,000 towards a £3.5 million project to repair the roof at historic Dyrham Park.

Water is leaking through the lead-covered roof of the National Trust property, putting at risk the house and its important collections.

Their future now depends on vital repairs to replace the 22 tonnes of lead on the roof, along with 8,000 Welsh slates. Repairs are also needed to stonework, while a new heating system will replace an obsolete and inefficient oil boiler.

The National Trust said it had been able to find £3million for the project but has now launched a fund raising appeal to find the balance that will make the scheme possible.

The house contains some of the original Dutch-inspired interiors and a priceless collection of furniture and objects collected by 17th century colonial administrator William Blathwayt, including Dutch art and ceramics of the period.

But less attractive features currently include numerous plastic buckets to catch water as it comes in from the roof. For several years patch repairs on the roof have been carried out but each winter the problem becomes worse.

Cath Pye, the trust's general manager at Dyrham Park, said: "It has reached the point where the house needs a whole new roof.

"We need to take the lead sheets off and recycle them, recasting them on site, and also replace many of the Welsh slates on the edges of the roof.

"There is a lot of damaged stone work to repair and a new heating system will enable us to provide conservation heating, which will better protect the collection. By using a biomass boiler, it will not only be cheaper but a lot greener to run.

“The orangery is one of the earliest of its type and an important part of the house but it too need repairs to prevent damage caused by water from blocked gulleys and downpipes.”

Dyrham's traditional sand-cast lead roof is more than 160 years old and its replacement will be the first major structural restoration since the Victorian era.

Cath said: "This is a major project but it will give us a roof which will last over 100 years and safeguard the contents of a very significant house.”

She said an existing oil-fired boiler was 20 years old and posed a serious fire risk to the house and collection, as well as being inefficient.

Curator Rupert Goulding said the work was crucial to protect important collections which had been in the house for 400 years.

He said: "We are fortunate that inside Dyrham much of the original collection built up by William Blathwayt has survived to show the house in the style he planned."

Every year more than 160,000 visitors go to Dyrham, which will remain open during the building work - due to start in early 2015 if the appeal is successful.