A city of Janesville official says chemical maker Abitec’s plan to rebuild its south-side factory with a new shell built around the current factory is unusual — if not a first in the city.

Abitec wants to erect a second skin — an outer shell — around their existing factory building, which is on South Jackson Street just south of the former General Motors site.

Abitec would then have a slightly bigger factory space, which it plans to modernize with new manufacturing equipment. City planner Trae Meyer says he’s never seen an industrial revamp where a new, outer wall is built over an existing factory.

Meyer says the unique building method is for a simple reason: Abitec wants to continue manufacturing operations during construction.

Ohio-based Abitec produces lipid-based surfactants for food, pharmaceutical and other uses at its Janesville plant.