Graffiti vandals have attacked Nostell Priory.
The house and parkland estate was targeted on Wednesday, October 15.
Parts of the house, stables, footpaths, trees and children’s adventure play area were all defaced.
National Trust staff said parts of the estate including the trees and play areas could be cleaned quickly.
But damage to the building’s 300-year-old stonework would be expensive to repair.
Nostell Priory and parkland general manager Jenny Layfield said: “We are incredibly disappointed that the beauty of Nostell has been compromised by such mindless behaviour.
“The graffiti mainly comprises swearing and is generally offensive but it will take some time to remove.
“We are working with a specialist to remove the graffiti carefully and sensitively from the historic buildings.
“This will be at considerable cost to the National Trust.”
Staff are currently getting estimates from contractors and predict it could take a couple of days to remove the graffiti once someone is appointed.
Mrs Layfield said the charity relied on support from visitors to help care for the estate.
She added: “This unexpected vandalism means that in the short term, many local people who visit the house, gardens and parkland for relaxing walks and scenery on their doorstep, will sadly have their visit impaired.”
Anyone with any information should contact Police on 101, quoting the reference number 457.
The estate will remain open despite the vandalism.