A fire that started in a dustbin spread along a fence to a pair of semi-detached homes in Cranesgate South, Whaplode St Catherine, in the early hours of today (Monday).
Five metres of fence, a gate, a UPVC side door and the hallway were severely damaged by fire at one home and there was severe heat and smoke damage to the rest of the house.
The neighbouring home had severe fire damage to its loft and barge board.
Residents - four adults and a child - escaped to back gardens and there were no reports of injuries.
Fire crews from Spalding, Holbeach and Long Sutton were called to the blaze shortly before 3.15am.
Lincolnshire Fire and Rescue say the fire was caused by carelessly discarded smoking materials.
A spokesman said both homes had smoke detectors but neither activated, presumably because the fire started externally, in or near a dustbin.
Fire severely damaged a living room and loft at a bungalow in Kingsgate, Gedney Dyke, on Saturday lunchtime.
The occupants - two adults and a child - were waiting outside as fire crews arrived.
Lincolnshire Fire and Rescue said the blaze was started by a spark from an open fireplace in the living room.