No one was injured, but damages from the blaze will be high, Rampton said.
"It's a lot. I hate to even guess right now. It's in the millions (of dollars)," Rampton said.
As the family waited for owner Fred Hale to return from a vacation in Wyoming, Ron Hale said the business will reopen.
"I've already talked to my brother. He said 'It's just a setback, we're planning on rebuilding,'" Ron Hale said. "He's just a determined guy. He brought this thing through the first recession in the '80s -- he hung on through that and he's going to hang on through this."
Two employees inside the store were closing up around 6 p.m. Monday, but were unaware of the fire above them until emergency personnel arrived, Rampton said. The fire was very visible from outside, and Rampton said a passerby alerted the fire department.
Four ladder trucks and eight engines responded from South Davis Metro Fire, Layton, Kaysville, Farmington and Salt Lake City.
With the fire burning in the attic and the risk of structural collapse, firefighters were forced to fight defensively almost as soon as they arrived, Rampton said.
The cause of the fire was unknown Monday night, and crews were expected to continue working through the night to prevent flare-ups.
"We probably won't be able to get the investigators in there until (this) morning," Rampton said.
Fire personnel were immediately assigned to protect the Greenview Townhomes and other adjacent businesses, but they were not threatened by the blaze.
Colonial Building Supply originally began in Bountiful, said Ron Hale, who is now a contractor. Many family members have worked for the company over the years.
Fred Hale started the business in 1982 with his father, Lyle, Ron Hale said. Fred, the company president, bought his father's share two years ago and is in the process of buying the rest of the business from his brother Larry.
"We built this (Centerville building) in 1995," he said. "We're one of the only independent lumber yards left in Davis County. We service all the bigger contractors -- we're a big distributor of drywall."
Written by Standard-Examiner