Firefighters had to remove parts of the roof to extinguish what remained of the fire, and a thermal imaging camera had been used to check the house for hotspots.
The homeowners had been at work at the time of the fire and it was lucky the neighbours had raised the alarm, Mr McKenna said.
Neighbour Anne Miles said she had first noticed the smoke coming from the chimney.
"I thought why would they be having a fire on a beautiful day like today?
"And I went out a couple of times because my husband was doing the lawns and when I came out the third time I saw smoke coming out from under the eaves and above the guttering."
She and her husband Ian contacted the fire brigade and a neighbour to the rear of the house rushed on to the property to check there was no one at home.
"It was nice to be able to help, although we'd rather not have had to make that call but that's unfortunately the way it goes," Mr Miles said.
"Prompt action saved it from being a damn sight worse -- it could have been gutted."
The cause of the fire was still unknown and was being investigated.