The Role of Layout in Delivering Efficient, Successful Building Projects By Bryan Williams
Sitting somewhere between the point where structures are conceptu- alized and designed and when they’re physically erected, lies a vital phase of project success – construction layout. It’s where architect, engineer, and detailer ideas get translated to the real world. Reference and alignment from detailed drawings are transferred to the job site to facilitate construction and without them, work can’t start, much less succeed. The Critical Role of Layout Professionals When starting at bare dirt, surveyors or experienced general contractors will have established control points, usually beginning with a known point, such as a property corner. These indicators of key structural ge- ometry placement are based on detailed architectural design models. They are established based on measurement and calculation of precise distances and elevations relative to the initial reference points. These control points are then used to transfer reference points to the actual structure that are used by the many contracted trades. These measurements must be carefully documented and checked against contract documents to ensure easements, setbacks, and prop- erty boundaries are within specification. To be effective, these markers must be durable and appropriate for the length of the project, easy for contractors to understand, and most importantly, accurate. Potential Problems with Inaccurate Layout Inaccurate layout points can lead to a wide range of problems. Just as a structure built on a weak or damaged foundation is bound to crumble, installation of a wall, pillar, or beam based on inaccurate layout points is likely to suffer one critical error after another. In most cases, these errors are discovered when contractors attempt to install building components. In this case, the result is a Request for Information (RFI) or change order that typically requires input from a detailer, or even the architect. Depending on its severity, the error could be a quick fix or create delays that eat away at the project budget and a contractor’s profit margin. When materials have been prefabricated based on erroneous measurements or calculations, the delay and cost of rework can escalate even further. In some cases, layout errors might not be discovered during a project’s initial erection phases and instead can impact the mechanical, electri- cals and plumbing (MEP) work, steel erection, or later phases of con- struction. In this case, rework is often more costly and time consum- ing as stakeholders scramble to make adjustments that accommodate
structural components already in place. In a worst-case scenario, layout errors that are not identified or properly prioritized during construction weaken or otherwise compromise the finished structure, creating a seri- ous safety hazard for occupants. It’s easy to see why accuracy is critically important. To do the job right, layout professionals must anticipate errors, rigorously check their work, understand design intent, communicate effectively with all stakeholders, and visualize the finished project. Modernizing Layout Traditionally, layout was a completely manual process that required at least two or more people, depending on a project’s size, and a host of tools including string, tape measures, levels, theodolite and leveling rods, plumb bobs, combination squares, and measuring wheels. Advances in technology such as pocket calculators, laser levels and distance meters, and electronic theodolites enhanced the process to some degree, but there was still a high potential for human error. With the introduction of the first electronic total stations in the early ‘70s and advances in CAD for generating, verifying, and placing points, the industry took another step in the right direction, but there were more improvements on the horizon. Today, steel and concrete layout professionals have an incredible array of tools and techniques at their disposal that professionals from the past would envy. These tools bring an unprecedented level of speed, efficiency, and accuracy to layout. In recent years, Robotic Total Stations (RTS) have dramatically im- proved construction layout. Taking a natural step beyond the capabili- ties of the electronic total stations of previous decades, an RTS reduces the opportunity for human error and frees up layout professionals for other, high priority work. An RTS can be controlled remotely using a tablet or controller, so one person can handle even the most complex layout tasks. In a head-to-head competition, one person using an RTS laid out 200 points in four hours, while two people working manually only laid out Robotic total stations have dramatically improved construction layout.
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february 2020
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