Fire crews were called to a house fire at Mill Green in Market Drayton, soon before 8pm on December 25.
The blaze, believed to have been caused by an electrical fault, damaged a building under construction attached to an existing house.
Firefighters sent from Market Drayton and Hodnet had to break into the plasterboard walls to find the source of the fire.
A statement from the Market Drayton crew said: "On arrival at the scene smoke was issuing from the roof and walls of a single storey sandstone construction building, which was attached to the main house.
"The incident commander was informed that there was no-one inside the building and that nobody had been injured.
"Following a dynamic risk assessment, the decision was made to commit four firefighters wearing breathing apparatus into the building, to begin rapid and assertive firefighting with a high pressure hose reel jet to prevent the fire spreading any further.
"Whilst the breathing apparatus crews were being committed, other firefighters working on the exterior of the building were pitching a ladder to gain access to the roof, laying out a hand-held main jet, positioning lighting and establishing a safety cordon.
"The breathing apparatus crews had to break into the ceiling and walls using ceiling hooks, to remove plasterboard to locate the extent of the fire spread and to extinguish it.
"Through great teamwork, physical effort and determination the crews managed to locate the furthest points that the fire had spread to in the roof and walls and stop its progress.
"Both crews were detained at the incident for approximately two and a half hours, whilst cutting away burnt timber work and damping down.
"Approximately 15 per cent of the building has been damaged by fire, with the remainder being damaged by heat and smoke.
"A specialist fire investigation officer attend the incident to help in establishing the origin of the fire. We can confirm that the fire is being treated as accidental with the cause being an electrical fault."