Seven years after developer Walnut Capital began the work of converting a former Nabisco plant into the mixed-use office, retail and hotel development known as Bakery Square, it’s about to embark on the expansion.

A host of dignitaries will join Walnut Capital principals Gregg Perelman and Todd Reidbord today in breaking ground on the first office building for Bakery Square 2.0, which sits across Penn Avenue from Bakery Square in Larimer.

The 218,000-square foot, six-story office building is one of two planned at the site, the location of the former Reizenstein Middle School. Together, the two buildings will feature 425,000 square feet of office space in a resurgent corridor that spans Larimer and East Liberty.

At Bakery Square, all 216,080 square feet of office space has been filled with tenants that include the University of Pittsburgh, Carnegie Mellon University, and Google, which has twice expanded at the location since moving in in 2011.

Walnut Capital also has attracted trendy retailers like Free People and Anthropologie. West Elm, an upscale contemporary furniture and housewares retailer, will open in September, leaving only 8,000 square feet of retail available in the complex.

“It proves in Pittsburgh that if you have a good location and a good product, it will work,” Mr. Reidbord said.

Walnut Capital also is off to a fast start at Bakery Square 2.0. Google already has committed to leasing about 70,000 square feet in the new office building. Mr. Reidbord said the developer is “very optimistic” about filling the rest and is talking to a number of potential tenants.

While Bakery Square features a 110-room Marriott SpringHill Suites Hotel, Bakery Square 2.0 will have a residential component — 350 apartments and 52 for-sale townhouses.

The first 175 apartments in a complex dubbed Bakery Living will be ready in June, with rents ranging from $1,150 for a studio to $3,200 for a 1,544-square-foot two-bedroom. One bedrooms and loft units also are available. About 50 units have been leased so far, Mr. Reidbord said.

Construction of the townhouses is expected to start this summer, with another round of apartment building scheduled for the fall.

The first of the two office buildings should be finished by the end of 2015. Construction of the second will start as “interest warrants it,” Mr. Reidbord said.

Just blocks away in East Liberty, Walnut Capital has fully leased all 117 apartments units in Walnut on Highland, the conversion of the historic Highland Building built by Pittsburgh industrialist Henry Clay Frick, and the adjacent Wallace Building.

“It’s been a huge success. It’s leased up faster than we expected. People love the Highland Building,” Mr. Reidbord said. “It’s hard to believe there’s a waiting list for apartments in East Liberty. It shows how things have changed over there.”

Walnut Capital also is in the “very preliminary stages” of a plan to purchase from East Liberty Development Inc. a group of properties adjacent to the Highland Building to convert them to apartments and retail, Mr. Reidbord said.

Mark Belko: mbelko@post-gazette.com or 412-263-1262.

First Published: April 17, 2014, 3:55 a.m.