Repairs are being carried out to the Grade II-listed former Surrey home of Sir Arthur Conan Doyle under an urgent works notice.
Waverley Borough Council, in Surrey, has sent workmen to Undershaw to put up scaffolding to support a metal roof and board up all accessible windows.
It said the building had deteriorated under the ownership of British Virgin Islands-registered Fossway Ltd.
The repairs have been welcomed by The Victorian Society.
The campaign group is calling for Undershaw to be given Grade I-listed status, and has also fought attempts by Fossway Ltd to convert the building into separate dwellings.
Sir Arthur lived there for almost 10 years at the turn of the 20th Century, during which time he wrote such classics as The Hound of the Baskervilles.
Its last use was as a hotel, but it has suffered water damage because of gaps in the roof, since becoming vacant
Waverley Council said the work would allow the building to dry out over the summer.
It also said that it would attempt to recover the repair costs from Fossway Ltd.
The Victorian Society's Dr Ian Dungavell said: "People around the world will thank Waverley Borough Council for stepping in to save Undershaw."
The society has appealed against a decision by the Department for Culture, Media and Sport not to make Undershaw a Grade I-listed building.