Such is the case for a recent project in Dartmouth, Nova Scotia. Ron LeBlanc, president of Pinchin LeBlanc Environmental Ltd. – a multidisciplinary consulting firm providing services related to environmental assessment, management, and control of hazardous materials – had driven past a Tilt-Up project numerous times and wanted to learn more about the construction method. He contacted the general contractor and engineer for that project, J.W. Lindsay Enterprises Ltd. of Dartmouth, Nova Scotia, to determine if they could construct a building for his company after seeing a 69,000-square-foot office/warehouse building that was constructed by the firm. The firm was quite surprised when he explained that he wanted a 5,000-square-foot building.
Although LeBlanc was originally skeptical that Tilt-Up was the proper construction method for his small building, he soon recognized the long-term benefits associated with the medium. “Beyond price, Tilt-Up was a more durable solution that required less maintenance,” said LeBlanc. “Further, our building location was in an industrial park and Tilt-Up fit the existing look and theme of the complex.”
Viewing this as a tremendous opportunity to dispel one of the largest myths surrounding Tilt-Up construction, J.W. Lindsay got to work developing creative design solutions to meet this project’s unique challenges. The first step in the design process was to conduct an extensive feasibility study, which involved meeting with a variety of staff members. They reviewed a host of intricate details with the team, such as whether or not a window would create a glare on a computer screen, how often the receptionist has to leave the desk to do work, and the importance of adding a training room. After assessing the staff’s needs and space requirements, J.W. Lindsay developed the floor plan and design concept from scratch. A design-build project in the truest sense of the word, the owner gave the firm freedom in the design to develop cost-effective and efficient options to make Tilt-Up an affordable solution.
As in any Tilt-Up project, planning began with the determination of the panel height and availability of cranes, selection of the casting surface, and then design of the panel dimension/height and layout/erection sequence. However, simply applying a scaled down approach from experience on a large Tilt-Up facility won't work. Simplicity is essential and each step, design element and material should be evaluated in terms of its value or cost impact on the project.
Designing for Economy and Efficiency
First and foremost, it is important to review all design features that add to the panel thickness as this not only impacts the budget through the amount of reinforcing steel and concrete, but also the size of the crane. For example, with a small footprint, the building probably does not have to be very tall, so the panels can be thin. Smaller and lighter panels greatly diminish the size of crane needed for lifting, and on a small project, the cost of a large crane can make or break the budget. To determine the necessary crane, determine the weight of the heaviest panel. As a general rule, a crawler crane capacity should be five times the heaviest panel, a conventional crane capacity four times, and a hydraulic crane capacity about 3.5 times the heaviest panel. While large projects typically dictate a crawler crane simply in order to speed erection, on a smaller project, a hydraulic crane may suffice. Although erection may be slower, the extra time associated with the smaller crane will greatly off-set the cost differential from the use of a crawler crane. In this case, small panels that were only 14.5-feet tall were designed. Further, an insulated form system was used for the foundation and frost wall, which allowed for shorter panels since a perimeter closure strip was not necessary. These design decisions decreased the necessary thickness of the panel to six inches, which reduced formwork and material costs. Further, the smaller panels enabled them to use a lower capacity crane. The 70-ton crane used for this project was rented at a significantly more economical rate than the traditional 140- to 300-ton crane that is used on most Tilt-Up projects.
A common mistake made in the design of smaller Tilt-Up facilities is the architectural treatment cast into the exterior of the panel. For example, if a 5.5-inch structural panel is required, opt for the 1/2-inch reveal instead of the 3/4-inch reveal. Chances are the variance in design will not be noticed; however, the decrease in the amount of concrete necessary can make a difference. Also, while 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 to 20 panels. As such, just because a double mat of reinforcement is necessary in one panel, it probably isn't required throughout the entire structure.
Other items to consider are roof drains. On a small structure, it is likely that you can specify only one roof drain, so be sure to locate it in an area that minimizes water travel. Corner detailing also can make a difference as 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.
Yet another example of small Tilt-Up success is the portfolio of C.E. Doyle, LLC, located in Campbellsport, Wis. The design-build firm has employed the Tilt-Up method for a wide range of projects and is responsible for building what many said could not be done.
For example, Tilt-Up was ideal for the needs of the Cadens Kennels & Hunt Club. Located in rural Campbellsport, the gun dog training facility boards up to 30 dogs at one time and is known for training animals from all over the country. The owner realized that an insulated Tilt-Up facility was ideal because the complete concrete envelope provides for easy wash-down and excellent durability. Further, the 1,200-square-foot concrete structure is easily maintained and serves as a very comfortable environment for the animals.
In
order to accommodate the small footprint and minimal casting area, the panels
were designed with efficiency in mind. Two different wall panel layouts and
configurations were utilized so the panels, eight in total, could be easily
stack-cast. Design efficiency also was simplified because no architectural
treatments were used in the panels, which was acceptable for this type of
facility. This project clearly shows that Tilt-Up is an effective solution for
any size project – no matter how small. Typically, the owner of a facility this
small would have to resort to masonry or metal. However, with the proper
planning, the firm was able to create a durable, cost-effective and efficient
structure using Tilt-Up.
Yet
another example is the 7,200-square-foot aircraft hanger boasting a 79-foot
clear span and a 60-foot-by-18-foot overhead hanger door constructed at the West
Bend Airport in West Bend, Wis. for Schmitz Ready Mix. Since the owner is in the
concrete business, they fully appreciated the benefits of a concrete building –
no matter how small. As such, Schmitz Ready Mix chose to utilize the ECO-Block
insulated concrete forms (ICF) system for the foundations and insulated Tilt-Up
walls for the panels. Because the small site was located on airport grounds,
accessibility was a major challenge. 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 due to their close proximity to the building
and crane. The casting area also was a major challenge as all 17 panels were
cast on the floor slab. This project would not have been as successful without
early determination regarding panel size and opening locations to ensure
economical stack-casting of panels. Although small, the structure is attractive.
Architectural banding was utilized with corporate colors to provide visual
relief to the concrete panels and the corporate logo and an airplane silhouette
were cast into the structure.