Six fire engines and around 40 firefighters were called to a fire at some outbuildings on Lakenheath in Southgate.
Two garden outbuildings were destroyed by fire and half of the rear of a neighbouring house was also damaged in the blaze.
The fire is believed to have been caused by sunlight reflecting off curved glass onto unknown combustible items.
A London Fire Brigade spokesperson said: “Fires caused by refracted sunlight can happen all year round and can be common.
"Our advice is to make sure that you keep mirrors, crystals, glass ornaments and other reflective items out of direct sunlight at all times.”
The Brigade’s top three sunlight safety tips:
The Brigade's 999 Control Officers received their first call about the fire at 1523. They deployed crews from Barnet, Edmonton, Tottenham, Hornsey, Southgate and Finchley fire stations. The incident was over by 1808.