Innovative Foundation Solution Receives Good Marks at Spanish House Immersion School
The new Spanish House Immersion School in Dallas gets an “A” for design and functionality, but the site it’s built on almost received a failing grade before construction began. “It was one of the most complex type of building sites you could have,” says Richard Atchison, whose firm, FORM studios Architecture, completed the new building for the elementary school after utilizing an innovative solution from Tella Firma to build a solid foundation on unsolid ground.
When FORM studios began planning for the new school near White Rock Lake in Dallas, it found the building site less than ideal for a standard foundation on piers. The site was located in a former flood plain, near a park and golf course, and featured the deep clay soil that is typical of neighborhoods in and around East Dallas. To make matters worse, the low lying elevation required 8 feet of land fill to elevate the building pad above flood plain levels before foundation work could begin.
The construction team was worried about potential soil movement that might cause a traditional foundation to become unstable and fail over time. Soil remediation was one option, which would require a 10-12 foot excavation before layering in new soil and non-expansive fill to prevent further expansion, but this method would add $3-5 per square foot and add more than a month to the construction schedule. Water or chemical injection was not an option for this site because of the high water table and environmental concerns.
The potential vertical rise (PVR) of the soil suggested that a suspended foundation and pier solution were required. In addition, the high water table meant the drillers would probably hit water as they installed the piers. Seeking a more affordable solution that wouldn’t require the additional expense of remediation, the team first considered bell piers to avoid the water table, and also considered a slab-on-void box foundation, which would cost between $25-30 per square foot.
Then the team learned about Tella Firma Foundations from TEXCON concrete contractors, which had experience installing more than 100 foundations utilizing the Tella Firma process in residential construction. Tella Firma uses a field-tested, patented process to elevate a slab-on-grade foundation using piers, to create a protective void between the ground and the foundation itself. Tella Firma’s solution for the Spanish House school would include an 8-inch raised foundation that isolates the slab from active soils and guards it from unexpected movement.
The Tella Firma suspended solution works well when high PVR and settlement are present on a site, which was the case for the Spanish House school. The elevator in the building still required a slab-on-void box foundation on four piers to support the additional weight, with an 8-inch void to match the Tella Firma foundation, which was lifted around the elevator pit. The foundation also was designed to support and counterbalance a scissor-lift platform used during construction and the installation of plumbing and other components.
The project was completed on time and on budget during a 7-month construction schedule, ready to open for the new school year in August 2016. Atchison said he was pleasantly surprised with the outcome of the building’s foundation, and noted that FORM studios would have been unable to complete the project on budget otherwise. In total, the Tella Firma solution saved the builder close to $100,000, and the school was able to consider additional design features based on this savings.
FORM studios is now working with Tella Firma on The Kingdom Life Church project in Frisco, Texas, and Atchison says the excellent report card from the Spanish House Immersion School means his firm will definitely work with Tella Firma on other projects.