Crews responded to the outbuilding on the 13000 block of N. Fellows Avenue around 10:45 a.m., according to the Los Angeles Fire Department.
Sustained winds amid a red flag warning throughout the region created a challenge for firefighters but the flames were extinguished within an hour.
About a dozen horses at an adjacent property had been under consideration to be evacuated, but crews were able to protect the animals.
The LAFD said there were "reports of a patient" but firefighters did not find anybody at the scene that required medical attention.
The cause of the fire is under investigation.