This is the astonishing moment a grader nudges a wall of a near-demolished home into the side of the next-door house trapping Kate Paterson, who uses a wheelchair, inside.

The disastrous two seconds comes near the end of the day when the concrete Auckland home is almost levelled, bar a side wall.

Two graders with claw grips had tackled the demolition of the Pt Chevalier home throughout the day, systematically working through the property until an outer shell remained.

But the catastrophic moment comes at 7.45pm when a grader touched the final concrete side - now on a precarious lean - causing it to smash into the neighbouring wooden bungalow and demolishing a wooden fence, which is crushed under the weight.

The near century-old bungalow offers little resistance to the heavy concrete block wall as it smashes into the side of the house, it's chimney puncturing the front bedroom wall.

A bystander can be heard yelling "No" as the wall disintegrates across the driveway blocking any chance of escape for the resident, who uses a wheelchair.

A cloud of dust rises but the digger drivers seem oblivious to the carnage and imminent danger as gas escapes from a ruptured pipe.

"You idiots," yells a woman.

"Hey, it's gas. Turn your machine off, it's gas," says another bystander.

The hiss of the escaping flammable fuel can be heard as people scream at the drivers to stop work and get out of the property as fears of an explosion grow.

Inside the wrecked property Paterson could only urge her children to leave while she waited for emergency services.

Her home was now unlivable after the chimney pierced her bedroom, leaving a deep gash in the home's weatherboards and severing the gas.

Smashed concrete blocks, windows and tin roof sheeting lies piled on the property's driveway, burying the side wooden fence.

Paterson and neighbours who witnessed the collapse said they repeatedly told the owner of the concrete house the demolition was unsafe and needed to stop. Worksafe was also contacted at least five times.

Stan Schwalger said he could see partway through the demolition process the wall on was out of plumb and would fall across the driveway.

"He was yelling at them to stop, not to pull the wall over," said Paterson.

She said the owner had been asked to come on site and witness for himself the demolition operation.

The road was blocked for about two hours as workers fixed the gas leak and dealt with damaged power supplies.