A national engineering firm has expanded its presence at CenterPoint in Waltham.

Simpson Gumpertz & Heger has added 27,400 square feet at 41 Seyon St., one of two buildings at CenterPoint, bringing its total size in the building to more than 100,000 square feet.

Simpson Gumpertz & Heger designs, investigates, and rehabilitates structures and building enclosures. Their work encompasses building, transportation, water/wastewater, and nuclear/science/defense projects throughout the United States and in more than thirty countries.

Simpson Gumpertz’s expansion is part of an ongoing development program at CenterPoint, which just completed the exterior and lobby renovations at 43 Foundry Avenue, 41 Seyon Street’s sister building.

"We were thrilled to be able to facilitate Simpson Gumpertz’s growth, and retain the organization in a vibrant business-oriented community like Waltham," said Ted Saraceno, president of Saracen Properties, the developer of CenterPoint. "Combined with the completion of the renovations to 43 Foundry Avenue, we are carrying a lot of momentum into 2010."

CenterPoint, a joint venture between Saracen Properties and a Trammell Crow Company-sponsored real estate private equity fund, is a 500,000-square foot master-planned redevelopment and renovation of a former Raytheon research complex into a Class A office and research and development park. The property is located in the heart of Waltham, minutes from the intersection of Interstates 90 and 95 / Route 128.

Saracen Properties, a Waltham-based firm, provides development, construction, property/asset management and investment acquisition services. Saracen has developed and acquired over 4 million square feet of office and technology-related facilities in the Boston market, including One Washington in downtown Boston.