SOMERVILLE — Scott and Missy Peasley lost everything on a Sunday morning in February when a fire destroyed their home, their barn and killed several of their animals.

And the day before, the Peasleys found out they were expecting their second child.

“It was a lot to take in,” Missy Peasley said recently in their under-construction new house. “It seemed like a nightmare.”

Their new house is being built on the footprint of their old home at 85 Route 105, also known as Patricktown Road. The fire broke out while nobody was home and destroyed the structures in about an hour. Investigators were not able to determine the cause because there was nothing left to examine.

Peasley, 34, said the hardest thing for her and her husband, Scott, 39, in the aftermath of the fire was explaining everything to their son, Hunter, now 5.

“It was difficult hearing my son ask where his dogs were or where his cats were,” she said. “He saw the fire, so every once in a while he’d ask why our house burned. He’ll ask about the two dogs. He’ll ask questions we just can’t answer. He’ll say that he can’t remember Jenny and Squirty (the dogs), and that’s really difficult.”

But the parents told their son a few weeks after the fire that he would be a big brother, and having a new family member has helped.

“The distraction of his sister has helped a lot,” she said. “We told Hunter that it was his job to protect (his new sibling). He took on the role of big brother and made sure everything was OK.”

Peasley said the family is now concentrating on completing their new home and having life return to normal.

“It was stressful, because we lost our house, and now we’re having a baby” she said. “We were living in my parents’ basement and have to build a house quickly so we can get into the house and start our life again.”

The fast-moving morning fire leveled the main house and a barn quickly in part because of a strong wind. By the time firefighters arrived, the fire had engulfed the structures. The family lost several animals, including dogs, cats and pigs.

Homeowners insurance has paid for a majority of the rebuild, and friends and family are helping with construction. Peasley said they are still waiting for a check from their insurer for the estimated value of the contents of their house, close to $100,000.

Peasley hopes the new three-bedroom, three-bath house and barn will be completed by March.