The Algonquin Club, on Commonwealth Avenue. (Photo courtesy of Daderot / Public Domain)

Hexagon Properties has completed a $17.5 million acquisition of the Algonquin Club of Boston’s property, after gaining approvals last summer to update the 132-year-old Back Bay social club.

Members in February voted to approve the sale of 217 Commonwealth Ave. to the Brookline development firm led by philanthropist Sandra Edgerly, who offered $25 million at the time, the Boston Globe reported at the time.

The Boston Zoning Board of Appeals in August approved plans to increase the property’s guest rooms from six to 10 and add a roof deck and fitness center.

The updates are designed to increase and diversify the club membership, Brookline-based Hexagon Properties said.