The Historic Preservation Commission will consider approval of improvements on the rear side of the 1820 Collective hair salon Wednesday night.

The owner seeks to replace an enclosed staircase at the 18 W. William St. building with a two-story wood-framed covered one to create an additional spa treatment room on the first floor, and a storage vestibule on the second floor.

Staff support the proposed renovation as planned, according to a report. It said: “The owner has been cooperative and sensitive to the suggestions and guidance as provided by staff and the architectural standards of the historic district.”

The owner purchased the building in 1999 and has invested money to preserve and restore the more than 150-year-old building. The east side brick elevation was exposed to elements after 130 years when the adjacent West End Grill, 14 W. William St., was demolished in 2015.

Last year, the commission approved the owner to repair unintended damages to the exposed east side elevation, according to the report. It included the removal of a failing west rear addition. The owner will carry out that project this summer, but will use the space to create two additional parking spaces for the business.

The commission will meet at City Hall, 1 S. Sandusky St., 7 p.m. in council chambers.