Firefighters were called to a collapse at a building under refurbishment on Arcadia Avenue in Finchley.
Half of the outer brick wall on the ground and first floors of the building collapsed. A 50-metre cordon was in place whilst crews worked to make the scene safe. Two men were taken to hospital by London Ambulance Service crews.
The Brigade was called at 1350 and the incident was over for firefighters by 1458. One fire engine from Hendon Fire Station and two fire rescue units from Battersea and Croydon fire stations attended the scene.