A number of emergency services were sent to Mount Pleasant Road just after 11am.
The blaze took hold off the back of a house and a number of people were evacuated.
There are no reports of injuries at this time.
Six fire engines and around 40 firefighters tackled the blaze.
The conservatory of a semi-detached house was destroyed, and part of the ground floor, first floor and the roof were damaged by fire.
Two men were treated on scene by London Ambulance Service crews for smoke inhalation.
Firefighters removed and cooled an air cylinder to an ambient temperature as a precaution, as some cylinders can explode when exposed to heat.
The fire is believed to have been accidental, but the exact cause has been recorded as undetermined.
