The fire was reported just after 4 a.m. in the 200 block of South Naches Avenue.
Firefighters say the fire was intentionally set in an exterior wall before spreading quickly into living space and the attic. YFD was able to contain the fire 20 minutes after arriving, but the building was heavily damaged. Code enforcement officials will decide Friday whether it should be immediately torn down due to safety issues.
No one was living in the duplex at the time of the fire. The building was being renovated after an arsonist set fire to an exterior wall in October. Two families were living in the duplex at that time and were forced to move.
YFD is investigating both fires and is still looking the suspect or suspects responsible for them.