Two men have been called "very fortunate" to have escaped without serious injury after a Balcony collapsed at a construction site in Sydney's west.

Fire and Rescue Nsw crews helped two men aged in their 30s who suffered lacerations after the balcony on the second storey of a home collapsed on Perry Street, Kings Langley, just after 9am today.

The balcony had been braced from below but still collapsed.

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The two men reportedly managed to crawl out after the collapse.

Firefighters also put up an exclusion zone around the construction site.

Paramedics treated the two men at the scene for minor injuries; one man had a sore arm and the other a sore lower back.

Both men were taken to Westmead Hospital in a stable condition.

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NSW Ambulance Chief Inspector Brian Parsell said the men were "very lucky" to have escaped without serious injury.

"Both gentlemen were actually on the second story," he said.

"Unfortunately the footings of that wall gave way and the men ended up under the actual wall itself."

Chief Inspector Parsell said the wall the men were working on weighed about a tonne and a half.

"So they were very, very fortunate the injuries weren't more serious," he said.

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"This is a timely reminder that calling Triple Zero (000) for an emergency can be the difference between life and death," Fire and Rescue NSW Acting Superintendent Tim Hassiotis said.

Safe Work Australia will now investigate the incident.