Chris Sallmann's Ashburton unit was once an award-winning architectural showpiece. Now it looks like a fortress.

The 74-year-old retired contracts estimator has spent about $20,000 modifying his home after a spate of attempted break-ins along his street. High fences with spikes line the front yard. Two bollards block the driveway. The front windows are double-glazed and smash-proof. The large sliding glass door at the side – his most expensive renovation at $7,000 – is a centimetre thick and bulletproof.

"There are things that you could do that will protect you, and make you feel better," Sallmann said.

His garage holds a limited edition Audi and a red sports car he restored over 25 years. Inside, the walls are covered in Australian landscape paintings, including a portrait of his great-great-grandfather painted by five-time Archibald winner John Longstaff. Sallmann takes few holidays – "I don't even know where Bali is" – and poured his savings into making the home his sanctuary. Now he's poured more into making it theft-proof.

Sallmann isn't alone. Security retailers say residential customers are increasingly upgrading home protection systems after car thefts nearly doubled in the past three years. Data published this month shows insurance claims for stolen cars in Melbourne eclipsed all other capital cities combined. Victoria Police are now urging people to buy simple crime-prevention tools for their vehicles.

Over the past five years, Google searches for "steering wheel lock" have increased by more than 5,000 per cent nationwide.

James Strachan, of Melbourne-based Shug Bollards, said more Victorians were now buying bollards for residential use. "The problem with a security camera is they can still steal your car, where with a bollard it's going to take a little bit of effort at least," he said. He estimated about half his customers are now residential property owners.

Sales for bollards at Safety Xpress, a workplace safety retailer with an office in Keysborough, have grown by 23 per cent year-on-year as residential demand grows. Operations and people manager Alisha Dopper said: "We've definitely seen people wanting to invest in physical security as more of a physical deterrent, but also a visual deterrent."

The front door of Sallmann's home is made of steel with tungsten frames and three locks, fitting flush into the doorway to prevent it being levered open with a crowbar. A second heavy wooden door sits snugly in the frame with a solid brass deadlock. He also uses steering wheel and on-board diagnostics port locks, plus a signal-blocking Faraday key pouch to safeguard his cars.

Sallmann experienced a break-in some years ago, and the recent attempted burglaries along his street changed him from a comfortable retiree to "someone that lives on the edge." Even he admits the bulletproof glass may be overkill – but he's not taking chances.