Around 6000 homes were swamped by heavy rain during the wettest winter on record, with the average repair bill estimated at £30,000.
But Osbourne and wife Sharon face a payout of ten times that sum – even though they won’t be allowed to start work until the end of the year.
The Black Sabbath frontman tells the Daily Mail: “It’s been completely flooded. The rain has battered down the walls and seeped through everything. There’s water everywhere.
“We’ve been told it’s going to cost £300,000 to repair – but we can’t go about getting it fixed because it’s going to take nine months to dry out.
“The place is ruined.”
The Osbournes have relocated to their LA home until the fix-up job can be completed.