A power tool battery charger is believed to have caused a fire at the Ruataniwha Rowing Complex near Twizel.
Two fire crews were called to the blaze at 8.20pm on Tuesday, after the complex manager and caretaker, who live on the property, returned home to find smoke coming out of the shed.
Complex manager and caretaker Trevor Wilson said he didn't hesitate to ring the fire service.
There was moderate damage to the steel-framed building itself, but the inside was gutted and machinery destroyed.
"It wasn't too bad, we got away pretty lightly," Wilson said.
Wilson said the iron cladding would have to be replaced and the rest of the interior would have to be waterblasted.
He said it was hoped to get the complex back to normal as soon as possible, before the rowing season kicks off in a couple of months.
- The Timaru Herald