Police cordoned off Kwik Fit in Newbury last week after an industrial accident, local media has reported.
Customer, Steve Clarke was waiting outside the workshop at the time of the incident.
He said: “I was just getting my tyres done when I heard a big bang and looked around and saw a car on its roof.
“It looked quite serious.
“The ambulance was here in just a matter of minutes, it was really quick.”
A police spokesperson said: “Thames Valley Police officers were called at 3.03pm [Friday 23rd September) by the ambulance service following reports that a man had been injured in London Road, Newbury.
“The fire and ambulance service also attended the scene.
“A man sustained serious injuries and has been taken to hospital for treatment.”