The 10-year pact follows an extensive search in Boston to replace HNTB's operations at 75 State St. in the Financial District. "It's a nice property," GVA Williams principal John Hennessey says of 31 St. James Ave. Hennessey and GVA Williams colleague Peter Bean conducted the search on HNTB's behalf and represented the firm in negotiations with Capital Properties. Tim Lyne and Peter Conlin of CB Richard Ellis/New England acted on behalf of the landlord. The tenant is expected to relocate next month.

HNTB's deal follows a significant sublease earlier this year when Sun Life Retirement Services took 71,000 sf at the 31 St. James Ave. space rented to First Marblehead Corp. Sun Life is also relocating from the Financial District, joining a parade of companies migrating from the traditional CBD to Boston's Back Bay. The list includes several prominent law firms, but companies from other sectors as well. HNTB is an international leader in architecture and transportation infrastructure planning.

The trend westward to the Back Bay has pushed average asking rates ahead of the Financial District, especially for high-end space. According to the GVA Williams overview, class A towers in the Back Bay have an average asking rent of $74.77 per sf versus $68.83 per sf in the Financial District. The average asking rent for Boston overall is $52.16, says GVA Williams, which calls the Back Bay the tightest and most expensive in Boston. The direct vacancy rate is just 8%, according to the GVA Williams review.

Hennessey cites the Back Bay's rich list of amenities such as restaurants and shopping venues among the lures for his client. Constructed in 1922, the Park Square Building is stocked with its own unique retail offerings on the first floor, and was also desirable for being close to public transportation, Hennessey relays. The broker also praises the efforts of Capital Properties official Rob Fink in structuring the lease, calling Fink "a pleasure to do business with" and someone "who knows how to get deals done" amicably. "I think the building is really going to benefit from his involvement," says Hennessey. While Fink is a recent arrival to the building, Capital Properties has owned 31 St. James Ave. since 1997.