HEAT radiating from a chimney caused a wooden beam to catch fire at a home in Haconby.
Firefighters were called to the property in Hall Road at about 2.30am on Saturday.
The blaze caused severe damage to a beam in a wall cavity.
A spokesman for Lincolnshire Fire and Rescue said it was extinguished using a hose reel and by removing a wall.
Two people had been in the property at the time but are not believed to have been injured.