The Power House

Building Program – After standing vacant for nearly 30 years, the St. Louis Municipal Power House building in downtown St. Louis, opened as the new regional offices of the internationally-ranked architectural firm, Cannon Design, in September 2008. In 2007, the firm purchased the 19,000 sf building and provided all design, development, and construction management services for its restoration, renovation and adaptive reusean investment that represents the firms confidence in the future of the city of St. Louis.

Constructed in 1928, the Power House was an original part of the Municipal Service Building complex that still occupies an entire block of downtown St. Louisproviding parking space for city vehicles, a fire department and an electric substation. The Power House component of the complex, designated as a landmark by the National Historic Register, provided coal-fired steam heat to a dozen downtown buildings but was decommissioned by the City in 1980.

Design Concept – The buildings revival style exterior, featuring tall, arched windows on three street facades and fine terra cotta detailing, has been fully restored. New floors added within the buildings massive volume accommodate continuing growth, with mezzanines preserving the arched windows on the north and east elevations and providing gallery and exhibit space for use by the firm and the larger community.

Although the buildings exterior shell and original structural steel were fundamentally sound, reuse for a large, thriving design-focused architecture and engineering practice required a creative spatial solution that exploited the buildings massive volume in spite of its relatively small footprint. It also offered the opportunity to rethink the implications of the physical office environment on the practice at a time of significant change in the profession at large and for the regional office specificallyprojects of ever-increasing scale, new models of project delivery, and new technologies.

One of the major challenges was to design a space that would meet the firms desire for a new way of working: one that was intuitive, flexible and open. Another challenge involved remediating the siteremoving piles of toxic pigeon droppings and the lead paint covering the load-bearing steel trusswork, as well as removing contaminants that were found in the soil near one of the foundations.

Design Solution – On July 14, 2009, The Power House was awarded LEED Gold status by the U.S. Green Building Council USGBC. In pursuit of this significant achievement, the design team applied an integrated, holistic approach at every stage of the restoration/ rehabilitation process, with every component of the buildings interior new and designed to current life-safety codes and LEED standards.

The final design floats two separate floor plates above the ground floor inside the tall volume, thereby creating two extra floors and ample collaborative meeting space and workspaces for approximately 120 employees. In addition, an elevator shaft, kitchenettes on each floor, and two staircases located against the back wall in the northwest and southwest cornerswere all achieved within the historical building envelope. Within that original framework, a model shop and materials library plus a boardroom are carved out of the basement. On the roof, an oblong structure originally used to store coal conveyor equipment now houses another boardroom and staff lunchroom.

The revamped Power House features a three-story gallery formed by constructing two partial levels that, combined with the existing two floors and rooftop penthouse, create a total of 32,000 sf of office and conference space designed to facilitate the firms highly collaborative, team-oriented work approach. The new floors are set back from the buildings spectacular windows to maintain the buildings sense of transparency and volume and to create gallery space for the community as well as for corporate functions.

Materials and System Selection – The final design retains the original steel structure: a set of eight columns and trusswork. A new steel system supports the second and third floors, which cantilever out into the ground-floor gallery. These are faced in drywall and painted white. The interior, essentially an empty shell, was completely rehabilitated, with installation of HVAC, plumbing, and electrical infrastructure. External modifications include historically accurate replacement of windows in their original masonry openings and creation of a 3,500 sf urban garden.

With regards to green materials and system selection initiatives: storm water is collected in an on-site underground cistern for irrigation; light-colored roof materials reduce a heat-island effect; use of high-efficiency plumbing fixtures resulted in 33 reduction in water usage; application of insulated, low-E coated glass reduces energy consumption; 98.6 of existing walls, floors and roof structure have been reused; gypsum board waste was reused on site as backfill for the sideyard, to name a few.


Project Type


1100 Clark Avenue, St Louis, 63102,


  • Cannon Design