Bartlit Residence
Castle Pines, Colorado
8,000 Sq. Ft.
1997

Architect:  Lake|Flato

It is a rarity to have architects, engineers, fabricators, and contractors working together as harmoniously as we did with this project, and the cooperation is evident in the successful integration of architecture and engineering in this Colorado home.

This success was honored with a Texas Society of Architects Design Award in 2000. The design prompted juror Michael McKinnel, an architect from Boston, to state, “It was drawing on and extending a tradition of the modern in terms of Frank Lloyd Wright and Bruce Goff, which I think deserves to be nurtured.

The east side of the house is tucked into the side of a hill while the west side opens up to a spectacular view of the Rock Mountain State’s front range.

With the exception of the north-south spine and a few miscellaneous areas, all the roofs of the house are constructed of various exposed structural elements.

The two guest rooms east of the north-south spine are tucked into the hillside with a roof topped with sod. To support the sod on the roof structurally and to resist the earth pressures on the walls, a cast-in-place concrete structure was selected. Because headroom was tight, we used a 10-inch, flat plate concrete slab for the roof. To reduce the spans of the relatively thin slab (considering the load of the sod) and to eliminate turned-down concrete beams, we buried steel pipe columns in the interior walls.

Since the cast-in-place, standard gray concrete became the final exposed wall and ceiling finish, we paid special attention to the aesthetics of the joints in the forming, and we suspended the reinforcing steel in the roof slab to eliminate the need for chairs against the wood forms. The exposed concrete is a natural structural expression of a building partially built into a hill.

On the west side of the gallery, the family room, living room, and fitness room are situated to maximize the view of the mountains. Heavy timber is a natural structural choice for a residence, but the large spans and the snow loading made timber or laminated wood beams and columns unusually heavy in appearance to the architect. Together, Lake/Flato Architects and Datum Engineers decided that steel would be more appropriate for everyone's concerns.

The structural system selected for these "pods" is composed of perimeter four-inch diameter steel columns supporting eight-inch deep perimeter steel wide flanges that slope with the roof and support the wood deck.

The structure is kept relatively light and elegant by utilizing bracing rods concealed in strategically-located stone dad stud walls to stabilize the structure.

A horizontal, four-inch wide flange beam continues around the perimeter of each pod at door height to brace the glass wall laterally.

The roof deck is composed of layers of structural elements. The first layer is exposed, four-inch steel wide flanges at approximately three foot on center. The second layer, on top of the four-inch steel beams, is exposed 2x4s turned on their sides and spaced at approximately three foot on center. The 2x4s support an exposed 1x6 wood deck that is spaced with a _ inch gap with an acoustical fabric above. This assembly is the exposed ceiling. Above the 1x6 deck is a typical roof framing system composed of 2x8s at two foot on center, batt insulation, and plywood deck.

Figure 3 shows how the layers of the roof were assembled. The 2x8 joist at two foot on center provided a traditional location to install batt insulation. But, as seen in Figure 1, it also provided a space to install four-inch, steel wide flange cantilever outriggers to support the wood deck overhangs.

All of the structural steel connections to the pipe columns are welded for visual appeal, but the connections also provide continuity that minimizes the wind loading deflection about the weak axis of the wide flanges. This allows the steel shapes to be smaller.

This connection detail allows for essentially zero construction tolerances. Dimensioning and fabrication of the structure's steel elements were two of the most challenging tasks of the project, considering the irregular shape of the floor plan and the sloping roofs. But at the end, one of the most pleasant surprises was the lack of difficulty with the fabrication and erection of the structural steel.

The most significant contribution was the method of dimensioning the plans developed by Robert Trinidad of LakelFlato Architects.

Instead of the traditional dimensioning system used in the architectural profession, Trinidad created a two-dimensional grid for the site. The x, y, and z coordinates for each column was then shown on the documents at each column location. The z coordinate height was at the workpoint of each column, as shown on the sections.

This approach allowed the surveyor for Beck and Associates to locate the centerline of every column on the project accurately and for the fabricator to know the exact length.

The steel fabricator used the electronic files created by Lake/Flato to create the shop drawings. Knowing the x, y, and z coordinates of each column, the computer could accurately calculate the length, slope, and angle of every member in the structure.

The accuracy of the architectural drawings, the surveyor's layout, and the fabricator's shop drawings created a successfully-erected steel structure. There may have been minor erection or fabrication problems, but none were brought to my attention.

The ease with which this complex structure was erected is a testament to the entire team's cooperation in this part of the project. The architect's dimensioning system helped the surveyor and the fabricator do their jobs more effectively.

Lake|Flato's design approach and internal relationships brought out the best of the entire team. We were encouraged to suggest and propose concepts and ideas beyond the traditional role of the structural engineer.

The architect's sense of cooperation and teamwork is shown in the design of the outdoor arbor that shades the patio on the west side of the gallery. This space is a favorite area of the home. Utilizing 12-inch steel channel shapes and four-inch steel wide flanges found elsewhere in the house, we proposed a cable-supported steel structure cantilevering out over the patio to create the arbor.

The steel channels and cables were organized in a diagonal manner compatible with the angles created by the walls of the house adjacent to the patio. The completed arbor includes a glass roof with a perforated copper shade. Jakob cables with stainless steel connections add to the clean lines of the structure.