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Why Choose Tiltup Construction?
By Jim Yatzeck, PE, CCM, LEED AP and Gene Layne
MBP
Tilt-up concrete construction is no different than the old-fashioned barn raising techniques used to build the walls of a barn. Framers would create a barn structure by first constructing the wood columns and beams for the walls on the ground before raising each wall panel into place.
On projects using more traditional methods for construction, the walls are built with CMU load bearing masonry units and a brick veneer, or heavy gauge metal studs covered with sheathing, and faced with brick or stucco. Either approach is time-consuming, since it is a multistep process which involves different trades. In tilt-up construction, the walls are constructed in a horizontal position in individual panels, and on top of the building’s concrete slab-on-grade (see Photo #1). These panels are then lifted, or tilted, up into position around the building’s slab (see Photo #2). This means the tilt-up structure’s exterior wall is virtually completed when it is tilted into place.
The first step in the process is to construct the slab-on-grade floor of the building. A perimeter strip of the slab, known as the pour-back strip, is left out to allow access for setting and adjusting the wall panels once they are set. Sometimes additional temporary casting beds are needed if the slab-on-grade does not provide adequate space for constructing the panels, or alternately, if the panels can be cast one on top of another.
During the forming stage of each wall, workers form door and window openings prior to the placement of ready-mix concrete. The forms block out areas to exact dimensions for the windows and doors to fit into the building structure. Many miscellaneous items can also be cast-in at that time, including hooks for lifting the panels and openings for electrical outlets and junction boxes.
Once the panels have been poured and time is allowed for curing, each panel is then lifted with a large crane and spreader bar specifically designed for this type of construction. After the walls are in place, braces are strategically placed to hold the walls until the steel framing members are attached, which brings stability to the entire structure. The wall panels are shimmed to their final position and the remaining slab-on-grade, or pour back strip, is poured tight to the walls.
MBP recently completed a project that utilized the tilt-up method for construction. The project was a three-story, 60,000 square foot office building in Suffolk, Virginia. The tilt-up panels were formed and fully poured in just six weeks, and lifted in place in just 48 hours. We estimate that the exterior walls would have taken two to three times longer to build had they been constructed using load bearing masonry and a brick veneer finish. The local neighbors and businesses were astonished to see a building get constructed literally overnight.
The Tilt-Up Concrete Association (TCA) was created in 1986 to establish standards and practices and to ensure continued growth in quality and acceptance of this method of construction. According to the TCA, tilt-up concrete construction has since been used in buildings as large as 1.7 million square feet, with individual panels reaching as high as 91 feet and weighing 150 tons. The TCA reports that 15% of all industrial buildings in the U.S. were created using tilt-up construction. It is growing at an annual rate of almost 20% and is used in over 650 million square feet of new building construction each year. In Texas and other Sunbelt states, tilt-up accounts for as much as 75% of new one-story commercial building construction. General contractors, design-build contractors and builders in Mexico, Canada and Australia are also using tilt-up concrete construction more often.
There are many advantages with the tilt-up method over steel buildings or more traditional construction. A one- to two-story structure larger than 50,000 square feet with less than 50% wall opening space is a good fit for tilt-up concrete construction. Some advantages include:
Reduced Construction Costs
Tilt-up construction offers several construction cost savings. Materials used are normally available locally rather than having to order from a manufacturer and have the material shipped to the project site. For example, structural steel can take several months for the shop drawings process, detailing, fabrication, shipping, and installation. Raw material costs are lower and can be delivered on an as-needed basis. Additionally, the project labor crews are typically smaller than the workforce on traditional construction projects and can be pooled from local labor forces, thus reducing labor costs. Typically, the larger the footprint of the building, the more project costs can be reduced.
Fast Construction Schedule
Tilt-up construction enhances the ability to reduce the project’s time and therefore delivers the building in less time than it takes for traditional construction. Setting tilt-up panels is faster than building walls via traditional construction techniques. Work can also be performed earlier inside the building on a tilt-up project. This allows the different phases of the project to overlap. Since materials are procured locally, material delay is eliminated from the outset.
Safety
Tilt-up concrete is safe if performed properly. Most of the work is done from the ground, reducing the risks caused by falls from scaffolding or ladders.
Aesthetics
Each wall panel is custom designed. Coloring can be added to the concrete, as well as curved walls. Brick embeds can be added prior to casting the panels, so that the exposed, finished product will have the appearance of a brick veneer.
Although this method has a long history, the practice is relatively new in the construction industry. However, it is fast becoming the method of choice for constructing modern warehouses, big box retail centers, office and storage buildings and other types of commercial facilities. Over the years, engineers have continued to refine the tilt-up process, allowing general contractors to offer a broader range of capabilities.
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