DENVER (CBS4) – An investigation is underway at a home in Denver’s Park Hill neighborhood after its roof collapsed Sunday night.

Shortly before 9 p.m., a woman inside the home wasn’t aware the roof was collapsing. A neighbor said he heard the roof crumbling and went over and helped the woman and her pet safely out of the home on East Colfax Avenue and Hudson Street before the roof began to give way.

Officials with the Denver Fire Department say work was being done on the house at the time, and some of the new roofing materials had been delivered to the top of the roof before it gave way.

On Monday morning the roof could be seen pulling away from the upper portion of the home, and part of the roof ended up on the vehicle in the driveway.

A structural engineer determined the home isn’t safe.

(credit: CBS)

(credit: CBS)

The Denver Fire Department believes new shingles and associated materials were too concentrated in one area of the roof.

“It appears the bulk of the load was on top of the weight bearing portion of the roof,” Denver Fire spokeswoman Melissa Taylor said. “It just seems to have collapsed into the attic.”

The owner wasn’t home when the roof collapsed, but her mother was staying there. A fence was put around the house, signifying that it is unsafe to occupy.

When doing roof work on a house built before 1955 the homeowner should insist that the roofer inspects the attic to make sure it can handle the weight of new shingles piled on the roof.

(credit: CBS)

(credit: CBS)

Bunching new shingles in one area before they’re nailed to the roof is a mistake, according to All Around Roofing of Arvada.

“I have rarely heard of that happening. It’s very unacceptable, obviously,” said All Around Roofing owner Stephen Simpkin. “They should disperse them across the roof line, usually in stacks of three across the ridges about four feet down from the ridge line, and they use tow boards to keep them from sliding down.

Simpkin said if a homeowner notices shingles stacked improperly to contact the roofing company.

“The homeowner should call their project manager immediately, call the company that they’re working with and let them know so they can contact the supplier to remove those shingles immediately,” he said.

The roofer, Dan Anthone of Infinity Roofing, told CSB4 it’s out of his realm to comment on whether the shingles were stacked properly. He says he’s working with the homeowner.