In one of the first large-scale, load-bearing wall projects of the 21st century, the Wylie, TX, Municipal Complex is defined by a 770-foot-long limestone wall that unites the project’s various components

For the architects at Holzman Moss Bottino Architecture, the task of building a 770-foot, load-bearing limestone wall for the Wylie, TX, Municipal Complex was a matter of following the fundamentals of traditional stone masonry. Now complete, the Texas limestone wall stands as a unique architectural achievement in 21st century architecture.

Located in the booming region of North Dallas, the Wylie Municipal Complex has three distinct components: City Hall — combining all City offices, a municipal recreation center, and the public library.

In conceiving a design for the project, Holzman Moss Bottino had three goals. They wanted an iconic structure to last over 100 years, to express fundamental principles of sustainability and to connect users to the natural landscape of the former ranch site.

Ultimately, a 770-foot, load-bearing wall of Permian Sea Coral limestone — quarried and processed by TexaStone Quarries of Garden City, TX — met all of these design goals while also connecting the complex’s three separate elements.

Designed to LEED Silver Certification, the project’s use of Texas limestone gained the project points for using a material sourced within 500 miles of the site. Additionally, the architectural firm has developed a collaborative relationship with TexaStone Quarries over the years “We have worked With them a number of times before, and we have a very good history,” explained Malcolm Holzman, FAIA, Partner at Holzman Moss Bottino. “They are willing to try and work with stone in new ways with us.”

The wall utilizes split-face pieces of limestone in a doublewythe assembly, and the load-bearing stone is used to support roof and floor loads — serving as both a structural element and the facing of the wall on the exterior and the interior of the building.

In selecting the material, representatives from the architecture firm made a visit to TexaStone Quarries to examine the material and its production.

The Permian Sea Coral limestone was used to create three different elements, according to Nestor Bottino, AIA, Partner at Holzman Moss Bottino. There are split-face ashlar pieces That make up the wall facing, headers in a smooth finish — some with the Texas star carved into the surface — and larger blocks that serve as supports for the lintels at the two entry portals. “We went through sample panels at the quarry, and then there were mock-ups and revised mockups,” Bottino said. “We had to make sure that the split pieces projected out. At first, the masons had work that was fairly flush, and of course we wanted the opposite of that. We also had some discussions on how to rake the joints in order to get the shadowing we were looking for.”

BUILDING A LOAD-BEARING WALL

Despite the mass of the load-bearing wall and the rarity of its use for a modernday building project, its construction was relatively straightforward. “There were some skeptics, but all you need is labor and intelligence,” Holzman explained. “And by doing this sort of application, you don’t need nearly as much steel. We had good structural engineers [Architectural Engineers Collaborative of Austin, TX] who were good about responding to current code and structural concerns.”

The wall varies in height as it runs the length of the complex. “It is 45 feet high at its highest point and around 11 feet at its lowest,” Bottino said, adding that the ashlar limestone pieces were as large as 12 inches tall and 36 inches long.

The mason for the project was DMG Masonry of Arlington, TX. During the process, crews from DMG would complete a 4-foot- High section of the exterior and interior wythes, and they would then spray waterproofing on the back of the exterior wythe.

A system of wire ties was used to hold the two wythes together. “There’s nothing wildly sophisticated about what we were doing,” Holzman said. “It was just important that it was done correctly.”

To maximize the stability of the loadbearing wall, rebar reinforcement was set every 10 feet. “Every 10 feet, there is vertical reinforcement,” Bottino explained. “Nothing is separate from the wall. The wall serves as the framework for the integral grouted pilasters.”

To support the elements that would be connected to the load-bearing wall, steel receiving plates were laid directly into the wall. In order to ensure that the masons could work independently of the steel contractors, DMG Masonry set bracing in place To support the wall until the steel was erected, and the bracing was ultimately removed as construction on the project progressed.

As the wall moves across the complex, thoughtful architectural detailing serves both practical and aesthetic goals. “Every 30 feet, there is a step in the wall,” Bottino explained. “There is a 4-inch step where a change in direction occurs and it also provides a shadow line. It also allowed us to have control joints without a large seam. The horizontal string courses step every 30 feet as well.”

At the end of the walls, the returns are comprised of full-width Permian Sea Coral limestone with a sawn finish.

STONE ELEMENTS THROUGHOUT

In addition to the windows, the 770-footlong wall is broken by two portals, which lead to outdoor entry courtyards that provide pedestrian access. One of the portals Is for the recreation center and library, and a second, larger one is for City Hall.

“The larger portal is 18 feet wide, while the smaller one is around 14 feet,” Bottino said. “We wanted the portals to be all stone, but the blocks had to be 4 feet tall and 6 feet thick, and transportation costs were an issue. We ended up using stone blocks [vertically], and the lintels are cast-in-place concrete. They actually work very well together.”

Natural stone also carries through to the interior elements at the Wylie Municipal Complex, including one wall surface in each of the following spaces: the City Hall Lobby, Council Chambers and Library interior. Reflecting the stone palette and texture of the main wall, these areas were clad with the same Permian Sea Coral limestone in a split-face finish. The interior face of the double-wythe split-face Permian Sea Coral limestone wall is visible in these area.

Each of the buildings in the complex features distinct shapes, creating unique rooms for the various functions taking place — from reading areas in the library to assembly rooms in City Hall. The overall goal was to create intimate areas for the community within the overall expansive facility.

For both interior and exterior spaces, the limestone is contrasted by iridescent metal tiles, which act as “luminous counterpoints to the syncopated rhythm of the stone wall,” according to the architects.

In addition to using local limestone, Holzman Moss Bottino specified a range of eco-friendly products for the Wylie Municipal Complex. Interior floor surfaces are covered in stained concrete, rubber made of recycled car tires and carpet tile of 100% post-production yarn.

Moreover, the overall site strategy and architecture were designed for energy savings. Given the complex’s linear layout, its east-west orientation locates it optimally in relation to the sun by reducing the amount of wall surface exposed to low eastern and western sun angles. By implementing a continuous north-facing clerestory to drive diffused natural light deep into the building, overall dependence on electric light is reduced.

Meanwhile the south side of the building features an overhang that approaches 40 feet in some places, with the depth calculated to block the intense summer sunlight while also allowing penetration of winter sun — thus reducing heating and cooling loads.

Speaking on the successful installation Of the load-bearing wall, the architects pointed to the collaboration with the stonemasons as critical in achieving the project goals. “Nothing fazed them,” Holzman said of DMG Masonry.