What is TiltUp?
“Have you ever driven past a construction site and seen massive cranes lifting huge panels of concrete in the air?
Have you watched with amazement as a new commercial building seems to spring into place, almost overnight?”
What you have witnessed is tilt-up construction, an innovative method for building office buildings, retail centres, warehouses, distribution centres, call centres, manufacturing facilities and other commercial and industrial structures with amazing speed, safety, and cost benefits.
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 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 sheeting. Regardless of which traditional approach is used, building the exterior walls is a time-consuming, multi-stepped process. A tilt-up building’s walls are cast horizontally in large slabs of concrete Tilt-up concrete columns being erected. called panels. The panels are then lifted, or tilted up, into position around the building’s perimeter. 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 South Africa. In spite of this, tiltwall construction is fast becoming the method of choice for constructing modern warehouses, call centres, distribution centres, retail stores, office and storage buildings and other types of industrial and commercial facilities.
AN OLD IDEA WITH NEW INNOVATIONS
The basic principle behind tilt-up construction – constructing walls horizontally, on the ground, and then lifting them into place – is not a new idea.
Evidence exists that some buildings constructed during the Roman Empire and the Middle Ages used this approach. More recently, American settlers in the 1800s gathered for “barn raisings” where they constructed the wooden walls for their buildings and tipped them up into place.
The 20th century marked the true beginnings of modern tiltwall construction. The development of reinforced concrete in the early 1900s allowed builders to create tilt-up commercial structures as we think of them today: One- to three-story structures built with walls comparable in thickness 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 of 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 tilt-up construction. These 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 in the USA 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 160,000 square meters, with individual panels reaching as high as 28 meters 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 6.1 Million square meters of new building construction each year. In Texas and other sunbelt US states, tilt-up accounts for as much as 75% of new one-story commercial building construction. Builders in Mexico, Canada, Australia and South Africa are also using tiltwall construction on an increasingly frequent basis.
HOW ARE TILTWALL BUILDINGS CONSTRUCTED?
The design of a tilt-up building incorporates the detailing of the columns and/or the wall panel elements to provide all the functional and architectural features of the building. Typically this would be door and window openings, special cut-outs and shapes and architectural texturing and mouldings.
Temporary ground slabs are cast with a high quality surface finish onto which the building components are cast. Specialised formwork is produced to precise dimensions as demanded by the detailed design. Purpose-designed lifting inserts and stay anchors are positioned and cast into the elements.
PRECAST CONCRETE, TILT-UP CONSTRUCTION AND TILTWALL: WHAT IS THE DIFFERENCE IN THESE TERMS?
Several terms – tilt-up panel construction, tiltwall construction, precast concrete buildingconstruction, and site-cast construction – are used to reference new or non-traditional concrete building processes. Do they all mean the same thing? If not, what are the differences?
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 formworks and pouring large concrete panels directly at the job site. The panels are then tilted up into position on prepared foundations or the building floor slab. Because the concrete tiltwall formwork is 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 panels have been measured at just over 20 meters across and almost 28 meters from top to bottom. Thus, architects and tilt-up concrete contractors have a great deal of flexibility in planning and creating their buildings.
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 formwork at the job site to create the panels. Instead, workers pre cast concrete panels at a large manufacturing facility. Because the precast concrete panels 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. 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.
The several casting beds required for the project are strategically positioned to align with the overall project plan and to enable efficient use of the crane.
The panel casting sequence forms an integral part of the project schedule and the tilt-up production plan ensures a continuous erection process. With good access and planning, as many as 30 panels a day can be erected thus giving early release of the building to the subsequent trades. This efficiency of construction translates into significant cost and time savings on a project.
The cured elements are lifted or “tilted up” by cranes onto pre-prepared foundations or floor slabs and fixed to structural columns or stayed with temporary, tubular, adjustable braces to concrete ground anchors or to the floor slab. Foundation-mounted panels have starter rebars that are tied in with the foundation reinforcing extensions and the panels are then cast in. This method would apply to pre-cast columns also. There are several variations to this process. After erection, any imperfections are rectified and braces removed after the foundation tie-in concrete has cured. Joints are caulked and finishes applied if required.