Ten fire engines and around 70 firefighters tackled a fire on Hawthorne Avenue in Kenton.
A disused church hall and car wash, two semi-detached houses and nine vehicles were destroyed by the blaze. Another three properties were damaged. One man was taken to hospital by London Ambulance Service crews.
Firefighters cooled and removed a 25kg propane cylinder as some cylinders can explode when exposed to heat.
Station Commander Paul Osborne, who was at the scene, said: "Around 100 people were evacuated from nearby blocks of flats, which firefighters protected with jets to try and stop the fire spreading.
"Crews worked extremely hard in hot, challenging, arduous conditions to protect local buildings and environment."
The Brigade's 999 Control Officers took 106 calls to the blaze.
The Brigade was called at 1618 and the fire was under control by 2142. Fire crews from Paddington, Heathrow, Ruislip, Harrow and surrounding fire stations were at the scene.
The cause of the fire is under investigation.