Waltham-based Vantage Builders Inc. has completed a 23,000-square-foot renovation Casa Systems Inc.’s headquarters in Andover.

Vantage renovated the second and third floors of the building at 100 Old River Road to allow Casa Systems to expand its footprint from the first floor. Casa purchased the three-story, Class A office building earlier this year.

The expanded space features 22 offices and room for 97 workstations, four conference rooms and a 16-person board room. It also includes a new presentation room that accommodates 60 people serves as a lunch room.

Vantage completely gutted the two floors to create an open area to build on plans from project architects, the McGuinness Group, and built a striking glass staircase between the second and third floors. The office features high-end millwork and attractive translucent partitions from 3form provide an intriguing design element while also boosting the interior’s natural light.

Vantage performed significant electrical and mechanical work including reconfiguring the office mechanical systems and installing a pre-action fire sprinkler system in the server room.  The server room was also outfitted with a separate cooling system.

Union Office Interiors furnished the location, choosing Allsteel products, including seating, conference room furniture, workstations and the reception station.

Casa Systems provides DOCSIS 3.0 CMTS products as well as universal EdgeQAM and intelligent video processing solutions for broadcast and unicast services.

“We are fortunate to work for some of the most interesting technology companies in the region, such as Casa Systems,” Ed Silva, principal of Vantage Builders, said in a statement.  “Their new headquarters space not only supports its tremendous growth, it also reflects the energy of the company.”