Mr Kamara was taken to the Royal London Hospital, but died soon after.
At the time of the accident, work at the Scottish Amicable development was behind schedule.
HBG Construction Southern pleaded guilty to a contravention of Section 3(1) of the Health and Safety at Work Act 1974, in that they failed to ensure that persons not in their employment were not exposed to risks to their safety.
Health and Safety Executive inspector Neil Stephens said: "This sad incident is an example of what can go wrong when planning and supervision is poor."
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