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Many project designs use a 3-D modeling program for planning, estimating, procurement, clash detection and other important tasks. Designing to this level of detail helps the project run more efficiently and stay on budget.

According to a 2012 McGraw-Hill Construction SmartMarket Report, nearly 90 percent of large and medium-to-large organizations use BIM—with BIM designers typically including architects and engineers and BIM users typically including contractors and owners. Nearly 73 percent of users that are fully engaged with BIM use this digital information for jobsite layout.

The main reason contractors use BIM for layout is because of the significant design detail needed in today’s complex buildings, such as curved walls that require exact positioning of drywall track and placing light fixtures in the designed location. In turn, this usually demands tighter locations for pipe and HVAC runs that need to be precisely in place before the finished wall is completed. Combine these complex design features with the driving force to reduce overall jobsite costs and the first place to look for profit improvement is with layout. Precise layout can cut costs by decreasing the amount of rework time on the jobsite.

Traditional Layout Conventional Total Station Robotic Total Station
# of Workers on a Layout Crew 221
# of Layout Crews/Project 111
Hours Worked/Week 404040
Hourly Cost/Person $75$75$75
# of Layout Points/Day 75150300
Total Cost Per Point $16$8$2

Cost Using Traditional Layout Methods

Before deciding whether BIM layout is right for a business, it is important to determine the costs involved. Assuming traditional methods are being used to lay out the jobsite (not advanced methods such as a robotic total station), add up the total number of rotating, point and line lasers required to do the work. For example, one rotating laser at $1,000, one point laser at $150 and one line laser at $250 adds up to a total tool investment of $1,400. The next piece of data that must be calculated is the labor cost of layout for a single point on the jobsite. Figure one crew with two workers logging 40 hours per week can achieve 75 points per day using traditional layout methods. Assuming an hourly cost per person of $75 (including benefits), the total cost per point is $16. Estimating the total number of points on the project is jobsite specific; for example, assume there are 2,000 points per floor for a standard six-story building. This includes anchor points, through penetrations, location of drywall track, and door and window openings for a total of 12,000 points for the project. Multiply the total number of points (12,000) by the cost per point ($16) and the layout costs $192,000 with an upfront tool investment of $1,400. Tech-Landing

Cost Using Total Station Methods

The average cost of a conventional total station can range from $6,000 to $12,000, and a robotic total station can range from $25,000 to $40,000 depending on packages, accessories and training. In most cases, a conventional (two-person) total station can be twice as productive as traditional methods, so substitute 150 for the number of layout points per day (as opposed to 75). The total cost per point using a mechanical total station is $8. Because robotic total stations use a single person for layout and can be used more efficiently, substitute 300 for the number of layout points and one for the number of workers on a layout crew to calculate a total cost per point of $2. For the same project size, the labor-related layout costs are $96,000 and $24,000, respectively, for using a conventional versus robotic total station. The benefit of using a total station is the significant reduction of layout time and cost. Return on investment calculators are available from different manufacturers of total stations to determine the total estimated layout costs for a specific project.

BIM Integration with Robotic Total Station for Layout

Most BIM design programs such as AutoCAD and REVIT can export layout data directly to the total station software. In some cases, total station manufacturers provide a software plug-in so the data can be extracted easily and seamlessly for jobsite layout. Usually, only the point X, Y, Z location is transferred to the total station for layout. To use the full functionality of the model for layout, attribute data for the BIM objects also should be transferred to the field. Using a robotic total station and associated software for jobsite layout can help ensure the point is in the correct position as accurately as possible in the least amount of time.

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