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So what is the difference between tilt-up and other types of construction?
In traditional forms of wall construction, the walls can be built with CMU blocks or blocks faced with brick. For some types of buildings, the exterior wall is made up of structural steel columns with heavy gauge metal studs covered with gyp sheathing, which is then faced with brick or stucco. Regardless which traditional approach is used, building the exterior walls is a time-consuming, multi-stepped process. A tiltwall building's walls are created horizontally in large slabs of concrete called panels. The panels are then lifted, or tilted up, into position around the building's slab. This means the tilt-up structure's exterior wall is virtually finished when it is tilted into place.
Tilt-up construction (also called tiltwall or tilt wall construction) has a long history, but its widespread use is a relatively new phenomenon. In spite of this, tiltwall construction is fast becoming the method of choice for constructing modern warehouses, call centers, distribution centers, retail stores, office and storage buildings and other types of industrial and commercial facilities.
Tilt-up Construction: An Old Idea With New Innovations
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The 20th century marked the true beginnings of modern tiltwall construction. The development of concrete reinforced with rebar in the early 1900s allows builders to create tilt-up commercial structures as we think of them today: One- to two-story structures built with walls comparable in width to those created with other methods of construction.
Even with this innovation, tilt-up construction did not gain wide acceptance until after World War II, when the mobile crane was first developed. The mobile crane allowed builders far greater ability to lift the massive panels into place, regardless where the job site happened to be. At about this time, ready-mix concrete was introduced to the industry, making tilt-up an even more viable alternative.
These new technologies occurred at precisely the right time. The late 1940s brought about a post-war boom in the construction of manufacturing and industrial facilities across the United States. Innovation, timing, and the need for large, warehouse-styled buildings opened the door for tiltwall construction. The three factors combined to encourage general contractors to embrace tilt-up as an economical means of delivering quality projects that meet even the most demanding specifications and schedules.
Over the years, industry experts have continued to refine and enhance the tiltwall process, allowing general contractors and design-build construction managers to drive greater capabilities and creativity in its use. In 1986 the Tilt-up Concrete Association (TCA) was created to establish processes and standards to ensure continued growth in quality and acceptance for this method of construction.
Tiltwall 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. Builders in Mexico, Canada and Australia are also using tiltwall construction on an increasingly frequent basis.
What is Tilt-up Construction? How Are Tiltwall Buildings Constructed?
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The crew then assembles the panel forms on the slab. Normally, the form is created with wooden pieces that are joined together. The forms act like a mold for the panels. They provide the panels' exact shape and size, doorways and window openings, and ensure the panels meet the design specifications and fit together properly. Next, workers tie in the steel grid of reinforcing bars into the form. They install inserts and embeds for lifting the panels and attaching them to the footing, the roof system, and to each other.
The slab beneath the forms is then cleaned of any debris or standing water, and workers pour concrete into the forms to create the panels.
Now comes the point where tilt-up construction, or tiltwall construction, gets its name.
Once the panels have solidified and the forms have been removed, the crew connects the first panel to a large crane with cables that hook into the inserts. The size of the crane depends on the height and weight of the panels, but it is typically two to three times the size of the largest panel. The crew also attaches braces to the panel. The crane lifts, or "tilts up," the panel from the slab into a vertical position above the footings. Workers help to guide the panel into position and the crane sets it into place. They connect the braces from the tiltwall panel to the slab, attach the panel's embeds to the footing, and disconnect the cables from the crane. The crew then moves to the next panel and repeats this process.
It's easy to be amazed as you watch the mobile crane tilt up a panel from the ground and set it into its place. Massive panels weighing 50,000 to 125,000 pounds or more dangle from the crane's long lines. The crew works as a team, setting the braces and guiding the panel with remarkable precision. The speed of the process is also remarkable; an experienced tiltwall crew can erect as many as 30 panels in a single day.
Once all the panels are erected, the crew apply finishes to the walls with sandblasting or painting. They also caulk joints and patch any imperfections in the walls. From this point the crew moves to the installation of the roof system and the trades begin their work inside the building.
Precast Concrete, Tilt-up Construction and Tiltwall: What's the Difference in These Terms?
As previously stated in this article, tilt-up and tiltwall are two terms used to describe the same process. For a tilt-up concrete building, the walls are created by assembling forms and pouring large slabs of concrete called panels directly at the job site. The panels are then tilted up into position around the building's slab. Because the concrete tiltwall forms are assembled and poured directly at the job site, no transportation of panels is required. One major benefit of this is that the size of the panels is limited only by the needs of the building and the strength of the concrete panels themselves.
Tiltwall panels can sometimes be extremely wide and/or tall. Tilt-up panel have been measured at just over 69 feet across and almost 93 feet from top to bottom. Thus, architects and tilt-up concrete contractors have a great deal of flexibility in planning and creating their buildings.
Because concrete tilt-up walls are poured outdoors, contractors are at the mercy of climatic conditions. When temperatures drop below freezing, curing the concrete panels becomes more difficult and expensive. This is why tilt-up construction is particularly popular in southern parts of the United States, where cold weather occurs less frequently. Certainly, tilt-up concrete buildings are built in northern areas, but the window of time for temperate weather is much smaller and less predictable, which can make construction schedules more difficult to meet.
The precast concrete building process is similar to tilt-up construction, but it addresses the challenges presented by weather. For precast concrete buildings, work crews do not set up forms at the job site to create the panels. Instead, workers pre cast concrete panels at a large manufacturing facility. Because the precast concrete forms are poured indoors, this activity can take place regardless the weather conditions. After curing, the precast concrete panels are trucked to the job site. From this point, precast concrete buildings are assembled in much the same manner as tiltwall buildings.
The fact that precast concrete walls are formed at a manufacturing facility resolves the weather issue, but presents a different limitation not found in tilt-up construction. Because the panels must be transported - sometimes over long distances - places a substantial limitation on how wide or tall each panel can be. It would be impossible to load precast panels that were 60 feet wide or 90 feet long onto trucks and transport them any distance. For a precast construction project, the panels must be smaller and more manageable to allow trucks to haul them over the road to their final destination. This places greater design restrictions on architects and limits the applications where precast construction can be used.
Clearly, tilt-up or tiltwall construction and precast concrete are similar processes. Because tilt-up affords more flexibility, it is the method of choice in locations where the weather allows it. Precast concrete is a suitable choice in circumstances where environmental factors and the construction schedule preclude tiltwall as a viable option.
Why Do Design/Build Contractors Choose Tilt-up Construction?
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But what are the advantages?
- Savings in Construction Costs - Tiltwall provides numerous construction cost savings. This method of construction uses locally available materials rather than ones that must be manufactured and shipped in. This means that raw material costs are lower, available when needed and less prone to price fluctuations. Tilt-up work crews are typically smaller than the crews used in traditional construction and are normally comprised of local labor. That translates to reduced labor costs. Because of the economies of scale, the larger the footprint for the building, the more these savings improve the project's total cost.
- Fast Construction Schedule - Tiltwall offers several opportunities to "compress" the schedule and deliver the building very quickly. Erecting the walls with tilt-up panels is faster than building walls using traditional construction techniques. The trades can begin work earlier in the process on a tilt-up project, which allows greater overlapping of project phases. Because the building is made of ready-mix concrete from local sources, the project is less likely to be affected by transportation delays as well. All these factors provide for a faster, more predictable schedule with fewer opportunities for delays and associated cost overruns.
- Safety - Tilt-up is a proven, safe method of construction. The vast majority of the project takes place on the ground rather than on scaffolding, reducing many of these risks normally faced by workers.
- Aesthetics - Tiltwall buildings are not prefabricated. Each one is custom-designed for the client's needs and preferences. A full range of building finishes, wall textures and adornments, colors, even curved walls, are available with this method. Tilt-up provides architects and designers with virtually unlimited flexibility in crafting a building that is functional, durable and aesthetically pleasing.
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The benefits of a project built with tiltwall construction continue long after it is completed:
- Durability - Tilt-up buildings are extremely durable. Many structures created in the 1940s are still in operation today, with little apparent wear. A testament to the strength of tilt-up construction, general contractors in earthquake-prone California now use this method for 90% of their one-story industrial building projects.
- Fire Safety - The concrete used in tilt-up panels meets the fire-resistance standards of even the most demanding building codes. For example, a 6.5" concrete wall offers a fire resistance rating of four hours or more. Tilt-up panels are also frequently used in the building's interior as fire walls. Tiltwall buildings offer real protection and safety for their tenants' employees, property and ongoing operations.
- Ease of Maintenance - Tiltwall buildings require little in the way of ongoing maintenance, outside of periodic cleaning and repainting as desired. Concrete is impervious to insect or rodent infestation, so this problem becomes a relative non-issue as well.
- Repairs and Expandability - In the event a wall is damaged by a forklift or truck, damages are typically more localized on a panel than in other types of structures, like steel buildings. Also, the modular design of the panels allows for easier repairs and expansion of the building.
- Security - Facilities that require positive security and management of the interior environment - prisons, classified manufacturing facilities, businesses with clean rooms - will appreciate the strength and control afforded by concrete and tilt-up buildings.
- Reduced Insurance Premiums - Because tiltwall buildings have superior fire resistance ratings and have been proven to withstand severe weather and earthquakes, these buildings typically enjoy better insurance rates than steel buildings or other types of structures.
- Reduced Operating Costs - Concrete provides excellent insulation, reducing the ongoing heating and cooling costs for the tenant. This insulation extends to sound as well as temperature. Workers in a tiltwall office building located in a noisy area will be less affected by the environment. By the same token, a manufacturing business that generates noise will have less effect on its neighbors and will find it easier to comply with local noise ordinances.
With a better understanding of these benefits, it's easy to see why many design / build contractors, construction managers and savvy building owners are opting for tilt-up over steel buildings or traditional construction. Delivering value, speed and responsiveness, quality, durability, reduced construction costs, and ongoing cost savings in operating expenses, tiltwall construction is the best choice for a wide range of commercial construction projects.
About The Author:
Named 2005 QUOIN / AGC General Contractor of the Year, Bob Moore Construction has been one of Texas's most respected commercial construction companies since 1946. Their portfolio includes a wide range of buildings, from warehouses and distribution centers to office buildings and retail stores. Whether they are providing general contractor, design / build or construction management services, their goal remains the same: to deliver quality construction projects on time and in budget
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