A Concrete Solution
- By Carl Clary, Joe Golden
- 06/01/08
Large-scale school design and construction has its own set of needs that point to precast as the medium of choice. The need for design flexibility and aesthetic character sees schools being configured with large common areas, expansive freespans, adaptable floor plans, and high headroom. The need to increase the size of schools means future expansions should be designed and erected quickly, optimizing the school district’s resources for the current community size. The need to ensure school safety and quality marks the meeting of local structure requirements, including fire separation between areas and adjacent structures, blast-resistant exteriors, and where necessary, the capability to withstand seismic events.
Precast has emerged as the effective and economical method to fulfilling the architectural needs and construction challenges of schools. From compressed construction schedules to reduced construction and operating costs to “green,” healthy, and quiet interiors — precast offers many advantages that enhance the educational mission of schools. It is clear why precast is becoming the favorite medium of a growing number of project teams involved with school construction.
Distinctive Architectural Styling
Whether schools are located in urban, historic, or high-tech suburban environments, precast handles such design and architectural constraints with an ease that results in individual character. Precast can be applied quickly and economically to virtually any project concept, conserving more resources for distinctive touches.
Replicate an existing appearance or establish a fresh look with precast. The rich palette of exterior architectural finishes and embellishments allows for shaping and sculpting distinctive designs. Shapes can be incorporated in a structure by means of acute corners, porticoes, entries, reveals, and returns. Precast also interfaces smoothly with glass and virtually all other modern building materials.
Surfaces can be freely designed with colored pigments, aggregates, inset brick, sandblasting, notches, and setbacks. Form liners can also be used to impart exterior surface texture. For example, a school can be designed with cast-in embellishments, such as names, emblems, images, or highlighting lines. A variety of surface treatments can be combined within a single element.
Meeting Structural Challenges
Precast manufacturers regularly employ highly-skilled engineers, making possible even the most aggressive of architectural designs. Precasters are experienced at developing creative structural solutions for unusual wear conditions, heavy loadings, and restricted land sites. Plus, new techniques are always being developed to accommodate ever-longer spans and special loadings required for schools. For example, spans up to 80 ft. provide gyms and auditoriums with the necessary high headroom and long-span open areas, and exterior shear walls, coupled with load bearing interior walls, open up floor plan options.
Precast can be designed to meet seismic, blast, and fire standards encountered for most school structures. Precast has high seismic withstanding capability under IBC standards. Precast also meets the most recent guidelines for blast resistance. Additionally, precast structures inherently provide an effective fire separation from adjacent areas and neighboring structures, which reduces insurance rates and accommodates contemporary security concerns.
Shortened Construction Schedule
With precast, the time to occupancy is often 30 percent less, which minimizes interim financing costs. These benefits are possible due to the shortened construction time of precast — by as much as four to 10 months.
Many reasons factor into the compressed schedule, including reduced detail design time and less masonry material, scaffolding, labor, insurance, and jobsite waste. Other factors include coincidental manufacturing of the precast framing system and foundation work, as well as less jobsite congestion, because the product can remain offsite until the foundation cures. Once it arrives at the jobsite, the product is quickly erected because precast wall panels, double tees, and flat slabs are designed for simple connection. Concentrated responsibility also benefits the schedule because, with precast, multiple building components come from a single source of supply.
Precast fits well into a design-build construction plan, allowing design and construction to proceed in “leap-frogging” phases. Precast employs fewer onsite trades throughout the project, due to simpler exterior and interior finish requirements and cast-in electrical and mechanical components, chases and passthroughs, as may be applicable. Interior trades are also able to get to work sooner without interference due to a fast construction schedule and the fact that shoring of the structure is not required. Plus, construction sequences are less hindered by weather conditions, lessening the impact of weather delays on the construction schedule.
For school expansions, the ability to fabricate the walls, floors, and roof while the foundations are being poured can make it possible to perform high-quality school expansions during the summer months, reducing risks to students and meeting the needs of growing populations.
Reduced Project Costs
Precast framing combines architectural and structural components into united pieces. The modular nature of precast makes it easy to design from standard pieces, allowing fast replication of classroom units, floors, and wings. This frees up funds normally spent on structural components in traditional construction, so schools can afford extra interior and exterior embellishments.
To further cut costs, essential utilities like electrical and plumbing, as well as external finishes, may be cast into the wall assembly. This maximizes interior floor space and provides inherent seismic and fire resistance. Precast also eliminates six or seven trades from the site throughout the project due to simpler finish requirements and the arrival of erection-ready wall panels. In addition to reduction of masonry material, scaffolding, labor, insurance, and jobsite waste, precast requires less equipment, minimizing equipment costs, site congestion, and site noise. This is especially beneficial when construction takes place near existing buildings or on an occupied campus.
Single Source of Supply Concentrates Responsibility
Precast’s single source of supply ensures that the precast project manager has the control necessary to bring the project in on track, to exacting quality standards and on budget. The project manager shepherds the project from the contract stage through completion, navigating through a wide variety of requirements, from building codes to government standards to tight construction schedules. And since precast components are fabricated under a plant-controlled manufacturing environment, the precast project manager is able to ensure that every component reflects the best practices, resulting in unmatched quality of manufacturing and erection.
A “Green,” Healthy Interior
Precast technology supports healthy interiors — a benefit to schools, which are expected to reflect a greater respect for the environment. Precast construction can assist schools in attaining high Leadership in Energy & Environmental Design (LEED) certification — up to 23 total points in five of the six LEED sections. The high-density precast wall panels are impermeable to moisture and have no dead spaces or cavities. This design is an effective guard against mold growth and unhealthy indoor air quality, as well as interior stains and interior damage. Precast also prevents outgassing from sealants, lubricants, foam, additives, synthetics, and adhesives widely used in conventional construction. The healthier products and high performance standards benefit both the community and building users.
Additionally, precast technology promotes quiet interiors with outstanding sound absorption (both floor-to-floor and outside-to-inside), a natural dampening effect on lateral vibrations and vibration isolation from rooftop mechanical systems. Precast framing systems also exhibit much lower vibration transmissions than steel framing, while cast-in wall panel insulation offers additional sound absorption capability.
Durability, Low Maintenance, and Reduced Operating Costs
The durability of precast provides schools with reduced costs after construction is complete. Precast framing and shear walls have a high structural integrity, aided by components such as galvanized and stainless steel embedded materials, so there is minimal wear over time and little maintenance required. Exterior walls are also low maintenance and abuse resistant, normally requiring only occasional cleaning and routine wall and joint maintenance every 15 to 20 years. Plus, the high-strength concrete in brick joints will not fail and will never require periodic repointing or resealing because the concrete’s bond strength is 5,000 psi.
Schools can further reduce energy costs when insulation is cast within precast wall panels. This is due to the high thermal mass of concrete, which minimizes the energy used to heat and cool. Plus, precast’s ability to design in future expansions allows schools to build structures for the current population, knowing that expansions are quick, high quality, and affordable. This will save money on paying for heating and cooling spaces that are under-utilized for several years as the community grows.
Concept Assistance
Precast engineers and project managers work with schools to develop a winning strategy that incorporates education mission essentials at an attractive project cost. They can help at the feasibility phase of a new school project, gaining buy-in by the entire project team and helping every member of the planning group catch the vision. They can also help catalog all the significant savings during construction and life-cycle operation, showing schools how to devote less to operating the school and more on actual instruction in the years to come. The result is getting more of what schools want — and sooner.
Making a Mark With Precast
Precast offers many compelling advantages for successful school projects, from cost efficiency to aesthetics to the “greenness” of the buildings. From every angle, precast meets the goals of any school: efficient facilities, motivating atmospheres, and healthy environments for both staff and students.
Carl Clary is a technical sales representative for Tindall Corporation’s South Carolina Division and is active in South Carolina’s chapter of Council of Educational Facility Planners, Intl. Joe Golden is a sales engineer for Tindall's Georgia Division and an associate member of AIA in Georgia, as well as a member of CEFPI, ASCE and ACI.