The overnight blaze, in Craigshill, in the Ballycraigy Estate, began on Monday at 1.45am.
It spread to a second boat destroying them both. Two front windows of the property were also damaged by the heat of the flames.
Two adults and their two young children were in the house at the time.
A police spokesperson said that they were not harmed.
The fire service was called to the house after a neighbour alerted them. It took firefighters around half an hour to bring the blaze under control.
Police believe the fire may have been started deliberately and are appealing for witnesses to contact them.