Calculating Cut and Fill Quantities: Modern Techniques and Best Practices

General and site contractors are often searching for the ideal way to calculate cut and fill quantities from grading plans. While there are a variety of approaches, certain methodologies may be better than others, depending on the contractor’s needs. This article will identify these approaches.

Key Points for Consideration

The first question contractors should ask is, “Should the quantity takeoff be automated?”

The answer for site excavation contractors is generally yes. Automation provides increased slotsdad speed, an improved audit trail, and greater accuracy. As a result of takeoff automation, costs are reduced, the number of bids is increased, and the contractor enjoys greater confidence and ease of use. As a rule, the return on investment is extremely high with quantity takeoff software.

Some contractors also find they can provide a higher level of service by documenting elevation adjustments required to arrive at a balanced site. For many general contractors, automating the takeoff process provides an increased ability to define the scope of the excavation subcontractor’s work, while providing the owner with important value engineering services.

Many general contractors also provide their excavation subs with cut and fill quantities, and then call for unit pricing from their subcontractors. An automated takeoff system for the general contractor makes it easy to define the quantities and volumes, empowering the generals to more effectively compare subcontractors’ bids.

The next important consideration is the available options for automating takeoffs, which include the following:

• Paper takeoff with a digitizer tablet. Most site excavation takeoffs have historically been performed using paper grading plans and a large format digitizer tablet. Contour lines, spot elevations, and areas were entered into the computer from the blueprint using the digitizer tablet. Once this information is digitized into the computer, site volumes are calculated along with a 3-D model of the existing and proposed site. The digitizer method is the ideal approach if contractors prefer to work with paper plans. However, many contractors are now receiving electronic files instead of paper plans, and the use of on-screen takeoff tools are gaining in popularity.
• File takeoff on-screen. The advantages of file takeoff onscreen are similar to those from using a digitizing tablet with paper plans, except that the mouse is used to digitize the areas and elevations on-screen. Ideally, on-screen programs should work with all file types, including AutoCAD DWG, PDF, and TIFF. The advantages of digitizing on-screen include reductions in paper cost, enhanced zoom and graphical control features, and the freedom to work any place where one has access to a computer. Many contractors find that the takeoff is quicker and more enjoyable to perform with an on-screen digitizer.
• Direct CAD file import. If contractors have the capability to receive AutoCAD DWG files, certain programs may enable them to perform a direct CAD import without the need to digitize. While this may sound ideal, success is dependent on the quality of the AutoCAD file. Many users find that they require a CAD program to clean and massage these files. Also, the cost of software for these solutions is substantially higher.
• Quantities obtained through Building Information Modeling (BIM). There has been much discussion in the industry about BIM and the ability to obtain quantities directly from the building model. At the present time, this has yet to be implemented for site excavation. Whether BIM will ever be applied to site excavation is an open question. If BIM is ever adopted, it may be many years in the future.

Preparing for Takeoff

The best takeoff method and software products for contractors are determined by their individual needs. Some contractors simply need quantity takeoff tools to estimate the volumes and cost of the project. Other contractors will require advanced, non-takeoff related features, such as global positioning system (GPS) interface, blade control, and site layout and design tools. However, these advanced features increase the complexity and cost of the software substantially.

Given the importance of the takeoff software to a contractor’s business, it is wise to compare the various programs offered by the leading developers of site excavation software. It is critical to evaluate software in comparison with the contractor’s needs. Internet demonstrations are commonly provided by the vendor. It is highly recommend that contractors receive a “satisfaction guarantee” on any software tools that are licensed. The true effectiveness of the software may not be known until used in a contractor’s day-to-day operations.

Some of the key players in this industry include the following:

• Vertigraph
• Agtek
• Trimble
• InSite
• Carlson Software
• Trakware
• ViewPoint
• Roctek

As vendors’ products are evaluated, contractors should think about training requirements, personnel, and total cost of ownership. The vendor’s track record and reputation in the industry should also be considered.

On-screen digitizing and direct file import continues to gain in popularity and market share.

The motivation to improve site excavation remains constant. The rates of return are substantial, often doubling output, for contractors engaged in site excavation takeoff.