Construction work on the protected building started last year.
Now a metal frame has been installed at the top on the property.
Due to the original building being surrounded by defensive ditches, little of the structure can be seen from public land.
Planning permission was granted in 2019 to convert the derelict building into a single six-bedroom dwelling.
It includes extensions and alterations, such as second floor accommodation at roof level and a pedestrian access bridge crossing the moat to meet the east elevation.
In August last year Building Control noted that this work, which had been applied for by Bambridge Limited, had
started, but was not yet complete.
The States of Guernsey sold the site near Perelle for £1m. last June.
The Victorian barracks is the only one its kind that has survived in Guernsey. It was built in 1855 when there were
concerns about French invasion.
After its military life ended, it was used by the Guernsey Surf Club and a Christian youth group as a headquarters. However in recent years the building has been empty and in need of work.
The States put it on the market in 2015 for more than £2m. But it took nearly four years to be sold, and then for only half its original asking price.
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