Small Tilt-Up Projects Can Be Profitable and Efficient
By Craig Olson, P.E. and Laurence Smith, P.E.
For years, site-cast, tilt-up concrete construction — a construction method where concrete wall panels are cast on site and lifted, or tilted, into place — was only believed to be a profitable and efficient construction method for building “big box”-type structures of 20,000 square feet or larger. Using this method, general contractors primarily could capitalize on economies of scale to build them quickly and economically.
But as tilt-up has evolved and adapted with new finishes and construction techniques, it also became possible for general contractors to build smaller structures of between 3,000 and 10,000 square feet using tilt-up concrete construction ― and to be profitable doing so.
The key to success clearly lies in pre-planning and addressing the design and construction process with a fresh approach, rather than replicating a scaled-down version of a large tilt-up facility.
A case study of tilt-up success in a smaller job is the construction of the 5,000-square-foot building for Pinchin LeBlanc Environmental Ltd., a Nova Scotia-based multidisciplinary consulting firm providing environmental assessment, management and control of hazardous materials.
Recognizing the Long-Term Benefits
Initially, Ron LeBlanc, president of the consulting firm, was skeptical about using tilt-up construction for his building. But he soon recognized the long-term benefits.
“Beyond price, tilt-up was a more durable solution that required less maintenance,” LeBlanc said. “Further, our building location was in an industrial park and tilt-up fit the existing look and theme of the complex.”
LeBlanc contracted with the general contracting and engineering firm, J.W. Lindsay Enterprises Ltd., which was building a 69,000-square-foot office/warehouse using tilt-up construction not far from his site. J.W. Lindsay was given the freedom to design and develop cost-effective and efficient options to make tilt-up an affordable solution.
The contractor began the design process with a feasibility study assessing staff needs and space requirements. The study included such intricate details as whether or not a window would create a glare on a computer screen and how often the receptionist had to leave her desk to work elsewhere in the building. After the study, J.W. Lindsay developed the floor plan and design concept.
As with any tilt-up project, planning began by determining panel dimensions, the availability of cranes and selecting the casting surface. After the panels were designed, the layout/erection sequence was planned.
Designing for Efficiency
Through the entire process, simplicity is essential, and each step, design element and material should be evaluated in terms of its value or cost impact on the project.
The 5,000-square-foot Pinchin LeBlanc Environmental Ltd. building was designed and built using tilt-up construction methods for efficiency, economy and durability.
It is important to begin the process by reviewing all the design features that add to the panel thickness and weight. These dimensions not only impact the budget because of the amount of reinforcing steel and concrete required, panel thickness and weight also dictate the size ― and cost — of the crane. And on a small project, the size of the crane could make or break the budget.
As a general rule, a crawler crane capacity should be five times heavier than the heaviest panel, a conventional crane capacity should be four times and a hydraulic crane capacity should be about 3.5 times the heaviest panel. To determine the type of crane necessary, first determine the weight of the heaviest panel.
Although large projects typically dictate the use of a crawler crane in order to speed panel erection, on a smaller project such as the Pinchin LeBlanc building, a hydraulic crane may suffice. True, a smaller hydraulic crane may take more time to erect the building, but those time-related costs will more than offset the much higher crawler crane rental cost, even for a shorter time.
With the Pinchin LeBlanc building, the panels were only 14.5-feet tall and an insulated form system was used for the foundation and frost wall. These design decisions meant that the panels would be only 6 inches thick, which reduced formwork and material costs.
The smaller panels also enabled the contractor to use a lower capacity, 70-ton crane, rather than a more traditional 140- to 300-ton crane used on most tilt-up projects.
Designing for Economy
The architectural treatment cast into the exterior of the panel can also lead to more savings if done properly for a smaller structure. For example, if a 5.5-inch structural panel is required, a 1/2-inch reveal, instead of a more expensive 3/4-inch reveal, may be all that’s needed. Chances are that no one will notice the design variance, but the decrease in the amount of concrete needed can make a difference.
Although there are great economies of scale realized when the panels are the same on a large structure, such repetition may equate to excess reinforcing steel or unnecessary concrete in a small structure containing only 10 or 20 panels. Just because a double mat of reinforcement is necessary in one panel doesn’t mean it’s required throughout the entire structure.
Corner detailing also can make a difference since the cost and formwork necessary for a smooth edge miter, sharp edge miter or modified butt joint can be drastically more expensive than a simple butt joint.
A Size and Accessibility Challenge Overcome
Another example where tilt-up construction was used successfully in a smaller structure is the 7,200-square-foot aircraft hangar at the West Bend Airport in West Bend, Wis. The hangar boasts a 79-foot clear span and a 60-foot-by-18-foot overhead hangar door. ECO-Block insulated concrete forms (ICF) were used for the foundation and insulated tilt-up walls for the panels.
The C.E. Doyle-built hangar at the West Bend Airport in Wisconsin. The hangar has a 79-foot clear span, and all the panels were cast on its floor slab.
Because the site was small and located on airport grounds, accessibility was a major challenge. Design and construction required 17 panels, but all the panels had to be cast on the hangar’s floor slab so as not to interfere with airport operations.
In addition, permission was required from the adjacent property owner to utilize space for staging, and coordination with the utility company was required during panel erection because power lines needed to be taken down because of their close proximity to the building and crane.
This project would not have been as successful without solid pre-planning and design, including panel size and opening locations, to ensure economical stack-casting. All this was accomplished.
Not only that, the design incorporated architectural banding using corporate colors to provide visual relief, the corporate logo and an airplane silhouette — all of which was cast into the structure ― so the small tilt-up hangar was not only cost-effective, it was attractive.
The Need for Speed
Beyond durability, speed is another major reason to select tilt-up construction for even the smallest structures.
In Theresa, Wis., town leaders wanted to build a 10,000-square-foot town hall in as short a time as possible. The building committee chose to use tilt-up construction for the facility, which included offices, meeting spaces and a garage, and construction was begun and completed in the heart of Wisconsin winter.
The building was completed in just three months, meeting the town’s requirements. In addition, banding was chosen to provide architectural relief in the panels to make the town hall attractive. And radiant heat was used in the garage area to complement the inherent thermal mass properties of the concrete panels.
The Pinchin LeBlanc building was also finished quickly. The walls for that building were cast in one week and erected in a mere four hours and 15 minutes, and LeBlanc had complete occupancy of the facility one month ahead of schedule.
When Thinking Small Tilt-Up, Think Simple
Tilt-up construction combines the advantages of reasonable cost with low maintenance, durability, speed of construction and minimal capital investment.
There are many creative design solutions that can be employed with tilt-up construction to make it an affordable option for smaller scale projects. When thinking small, keep the design options simple and many cost-effective options will be realized.
For more information about tilt-up construction, visit Tilt-Up Concrete Association (TCA) Web site at www.tilt-up.org, or call 319-895-6911.
Craig Olson, P.E. is senior project engineer for C.E. Doyle, LLC of Campbellsport, Wis. and a member of the Tilt-Up Concrete Association Technical Committee. For more information, e-mail Olson, or visit his company's Web site at www.cedoyle.com.
Laurence Smith, P.E. is project manager at J.W. Lindsay Enterprises Ltd. of Dartmouth, Nova Scotia and president-elect of TCA. For more information, e-mail Contact Smith, or visit his company's Web site at www.jwlindsay.ca.
Tilt-Up Tips for Small Structures
- Keep it simple: Avoid complex details or architectural elements. Simple buildings can be beautiful in their own way.
- Communicate: Keep the owner involved as much as possible so he or she will have a realistic expectation of the final product.
- Plan Early and Often: The only opportunity for saving money in a construction project is during the planning phase. Beyond that point, money can only be spent.