Airy Addition: A New Poolhouse

Project: Poolhouse complex, Washington, DC

Architect: Outerbridge Horsey Associates, PLLC, Washington, DC; Outerbridge Horsey, AIA, principal

General Contractor: BOWA Builders Inc., McLean, VA

To enhance an existing pool at a residence in Washington, DC, Outerbridge Horsey Associates, PLLC, was hired to build an 850 sq. ft.  poolhouse complex that provides tranquility and preserves the view from the house across the pool.

The structure, sited in the corner of the rear yard of the house, is on axis with the existing swimming pool. The ground level is an open garage/storage room, and the upper level contains the poolhouse complex, which is comprised of three separate structures – two pedimented brick pavilions that flank an open-air pergola. The pavilion on the south side encloses a changing room, while the one to the north has a bathroom. “The poolhouse serves various functions,” says Outerbridge Horsey, principal of the Washington, DC-based architecture firm. “It provides a sitting area near the pool for family and group activity and serves as a gathering and entertainment area, featuring a cooking area with the grill built into the terrace’s west wall.”

The pavilions are constructed of concrete-block-backed brick painted white. A wood frame and the pedimented roofs are covered with naturally finished Buckingham shingles. Horsey was careful to relate the pavilions to the house, simultaneously giving them their own character. “The pediment roofs complement the flat roof and the balustrade on the house, while giving the pavilions their own identity,” he says. The pergola features Tuscan-order fiberglass columns – similar to the porch columns on the house – with natural-finish white cedar joists and purlins.

Due to the 8-ft. grade change from the terrace level to the driveway at the storage-room level, railings at the west and south sides of the terrace were required. A decorative wrought-iron railing with an overlapped circular motif was installed at the south and a wrought-iron rectangular grid basket weave was used on the full-height fence railing.

The poolhouse interior features pitched beadboard ceilings and has a stucco finish to prevent moisture damage. “The stucco is applied over a galvanized metal lath, which is attached to the interior face of the concrete block,” explains Horsey. The bathroom includes a frameless shower partition, a porcelain sink, handmade ceramic tile and Pennsylvania bluestone flooring – which is also in the shower in smaller pieces. The flooring in the changing room is also bluestone.

The storage room is made of poured-in-place concrete walls with precast-concrete planks supporting the pavilions above. “Precast-concrete plank is unusual in residential design,” says Horsey, “but was used on this project in lieu of a cast-in-place slab due to the limited headroom in the ground floor. In addition to being thinner than a cast-in-place slab, it is also more economical and faster to erect.” The planks are covered with sheet membrane waterproofing. To match the existing paving around the pool, the architects used Pennsylvania bluestone for the terrace in a bordered diagonal pattern. The south wall has a steel beam spanning the two door openings so that the combined opening can be converted into a garage door at a later date.

The main challenge of the project was to maintain views and airflow. “There was a desire to preserve a sense of openness,” says Horsey. “The two-pavilion scheme with the pergola in the center was designed for that reason. The layout preserves the airflow and the views through the center of the space and reduces the impact of the mass of the combined bathroom and changing room areas.”

In addition, “maintaining adequate headroom in the garage/storage room below [slightly above 7 ft.] while providing an adequate structural support over a reasonably long span [18 ft.],” says Horsey, proved challenging as well.

Horsey overcame these challenges and the poolhouse complex was completed in July 2005. It not only complements the existing house but is elegant on its own.