A family whose home was torched by an arsonist as they slept say it could take them a year to return home.

After losing "everything from the toe-nail clippers to the potato masher", the Christchurch family of four are staying with friends as contractors gut their fire-ravaged home.

Single mother Andrea Phillips and her three children were sleeping in their Cottonwood St, Parklands home when someone entered their unlocked rumpus room and set it alight about 2.30am on March 22.

DEAN KOZANIC Single mother Andrea Phillips is rebuilding her family's life after an arsonist set their home alight as they slept on March 22.

The "crackling" blaze woke Phillips, who slept in a separate room to her daughter, Jessica, 11, upstairs. They ran downstairs through smoke, bursting into Phillips' sons' bedrooms to wake them.

Phillips, her daughter and sons Matt, 15, and Jacob, 17, made it out. Philips returned inside to grab a cellphone and keys to their cars.

"Then we moved our cars and literally stood there. All we had were the pyjamas that we were wearing and we just watched the house burn. There was nothing we could do."

CHRIS BOON The room where Andrea Phillips' son Matt, 15, was asleep. The rumpus room backs on to his bedroom.

It is hard for Phillips to revisit "the devastation" that was once their sanctuary. The fire trashed their bedrooms. Heatpumps have melted off the walls. A thick layer of soot has blackened the interior.

That someone lit the fire when it was obvious people were inside was harder to grasp, Phillips said.

It was the second deliberately-lit fire in the street that night. Down the road, someone set to a curtain through a window while a couple and their 2-year-old son slept inside. It did not take hold. Police suspect the incidents were linked.

CHRIS BOON Remains of the rumpus room at the rear of the house where the fire is believed to have started.

"The fact is that night they decided they were going to light a fire and didn't worry about the consequences," Phillips said.

"I know I had two minutes, two minutes more and the whole story would have been different.

"Four lives could have been lost that day, and it certainly hit me later that night that my kids could have gone. It's pretty devastating. I hope [the police] get them soon, because I don't want it to happen to anyone else, somebody else might not be as lucky as we were."

Detective Andrew Henderson said the police investigation was ongoing.

The children's schools had helped with new books and uniforms. Contents insurance would replace the rest.

"It's the whole house, everything is gone; toe-nail clippers right through to the potato masher, and everything in between beds, duchesses, clothes, everything."

The family sought refuge with friends and are on the look-out for rental home.

"[The insurance company] said eight months until it's finished, but realistically we are probably talking 10 and 11 months."