A new contemporary addition, which features cast-in-place reinforced concrete walls, was recently completed at the historic Mercer Museum in Doylestown, Pa. Philadelphia-based Voith & Mactavish Architects (VMA) designed the 13,000-sq.-ft. addition that provides flexible venues for traveling exhibitions, interactive programs for children, and educational spaces.

Mercer Castle was built by Henry Mercer in 1916 to showcase his collection of early American artifacts. Many of the artifacts are made of wood, so the historic castle was made of concrete to protect the collection in the event of a fire. VMA chose to use cast-in-place reinforced concrete as the new addition’s primary building material to match the existing structure. VMA worked with Bazella Group, Allentown, Pa., to replicate the cast-in-place reinforced concrete wall technique using modern technology, including formliners made from rubber imported from Europe and rough sawn lumber from Amish country. Delaware Valley Concrete Co. Inc., Hatboro, Pa., supplied the 4000-psi air-entrained special cement blend. The concrete was made using a cutom tint of Lehigh cement and pozzolan at a 0.45 w/c ratio. The walls required 625 total cubic yards of concrete, 461 cubic yards for the exterior walls, and 164 cubic yards for the retaining walls.

The Bucks County Historical Society commissioned the design and construction of the addition to expand the exhibition and programming capabilities. The new addition reorients the main building entry and parking lot, serves as an event venue and orientation space, and takes advantage of the gradually sloping grade to create an inviting entry plaza leading to the new main entrance.

Built partially underground, 16 feet below the original museum’s ground floor, the addition connects the two buildings with a grand staircase that doubles as a waiting area. Windows and glass skylights in the grand entry hall soften the castle’s heavy appearance by framing views of the historical structure.

Extensive sitework was required for new pedestrian and vehicular access, drop off, service, and expanded parking facilities. The site’s steep slope challenges were solved with a series of retaining walls, steps, and gently sloping grade changes.

Various sustainable features were incorporated into the design as part of the comprehensive stormwater management plan. These include a green roof, pervious paving, a rain garden, and native plantings throughout. The green roof is an important feature of the building as it is the primary view of the new addition from the existing building and the northernmost corner of the site. Use of the existing rooms on the ground floor helped to reduce the new construction footprint, allowing the museum to capture a dramatic outdoor courtyard surrounded by a panoramic view of the original concrete structure and the new addition.

The Mercer Museum addition provides a flexible framework for traveling exhibits and the opportunity to present the museum’s existing collections in a new light.

Daniela Holt Voith, AIA, LEED AP, IIDA, is Partner in Charge for Voith & Mactavish Architects.