Grading in Construction: Different Types of Land Grading and Steps to Create a Grading Plan

Grading in construction reshapes land to match a design plan. It involves the modification of land surfaces according to the desired design. This is achieved through the removal of excess material, excavation of high spots, and filling of low spots. The end result is an area of land leveled to have specific grades and slopes.

Grading is crucial for every construction activity. A proper foundation is made possible by proper grading. It is essential to note that the construction subgrade should be stable. Besides, water needs to drain away from any structure. Failure to do this results in accumulation of water and consequent erosion of the building’s foundation and weakening of the building’s structural integrity.

Grading in construction helps prepare the land to be used according to the specified purpose. Grading is essential in landscaping where there is a need to place topsoil and make appropriate slopes. In case of commercial property, grading creates parking lots and loading zones. Different land uses dictate different slope requirements. Civil engineers usually prepare the grading plans.

Practically, there are two types of elevations: existing and proposed. Construction teams use these to guide their work. This article discusses the different kinds of grading, the procedure of developing a grading plan, and the safety guidelines in length.

Types of Land Grading in Construction

There are many types of land grading. But each of them serves a different phase of the project. Rough grading is the first one, and final grading is the last one.

The primary purpose of rough grading is establishing the approximate slope and grade of the construction site. In reality, the task is performed by bulldozers, excavators, and motor graders. But instead of a finished grade, it provides a working platform. According to Vista Projects, the tolerance for rough grading is approximately ±0.25 ft from design grade.

The purpose of finish grading is establishing the final elevation and slope. Generally, it is done after subgrade preparation, utility installations, and compaction tests. Additionally, finish tolerances are stricter; they can be ±0.04 ft. Consequently, paving, foundations, and planting depend on them.

Final grading lays down the topsoil layer. Usually, teams lay topsoil during this phase. Hence, the topsoil layer ensures proper vegetation, seeding, and sodding.

Types of Site Grading by Project

The site grading requirements largely depend on the type of construction. The housing, commercial, and landscaping projects each have their own criteria for the maximum and minimum slope. However, the local specification determines the exact figures that should be used. Therefore, it is important to consult the specification before completing the design.

In housing developments, crews grade the individual lots so water flows to streets or storm systems. In other words, for instance, a lawn requires a minimum slope so that it can shed water. According to the Aurora city specifications, there should be a minimum slope of 2.0% for any lawn.
Commercial properties include grading of the parking lots, loading docks, and access roads. Specifically, there must be an adequate slope to drain without ponding. Moreover, Aurora requires that the parking lot has a slope of 0.50% to 3.0%. Besides, there must be stormwater management and proper overland flow.

Landscaping projects entail the plant beds, lawns, and swales. Therefore, the final grades must also facilitate planting and irrigation. For instance, a lawn swale must have enough fall to accommodate runoff.

However, city rules differ from national codes. Before the grading is done, it needs to be confirmed which rules apply to the site.

Steps to Create a Grading Plan

The grading process adheres to an ordered procedure whereby each step leads to the subsequent one. Otherwise, missing out on one step typically results in the need for redesign in most cases.

1. Conduct a topographic survey. Note that Aurora requires a signed and sealed topographic survey by a licensed surveyor or engineer. In addition, the survey should include 100 feet beyond the site.
2. Document existing conditions. These include utilities, fences, retaining walls, easements, streams, and wetlands. Additionally, Redmond requires utilities to be at least 5 feet from the retaining wall geogrid.
3. Indicate protected zones. Indicate retained tree driplines with a 5-foot setback. This ensures that grading stays out of this zone.
4. Set design elevations. These include building pads, road grades, and drainage outlets. Aurora requires that building floors be at least 1 foot above the 100-year base flood elevation or 2 feet where the tributary area is greater than 20 acres.
5. Contour lines. Existing contours are drawn as dashed lines while proposed contours are drawn as solid lines.
6. Spot elevations and slope arrows. Then place proposed spot elevations every 50 feet. Add downslope arrows depicting the calculated slopes.
7. Overland flow paths and storm structures. In addition, draw the flow paths with large arrows and rim elevations for every storm structure.
8. Cut and Fill Volumes. Present volumes in cubic yards. Plus, indicate cut and fill over eight feet, since they usually need a deviation.
9. Indicate retaining walls and steep slopes. Include the wall type, its top and bottom elevations, and the underdrain outlets. Next, indicate steep slopes with a 40% grade or higher and the necessary setback for them.
10. Draw legend, north point, scale, and professional stamp. For instance, Redmond applies the scale of 1″=20′. Finally, an authorized professional should prepare and certify the drawings.
11. Then submit the plan for review. Update the drawings according to the review and resubmit them.

Grading Process, Software, and Data Inputs

The grading procedure starts with digital design and culminates in validated field results. Teams finish each stage before they start the next. The first task is clearing of the site and removal of topsoil, then cutting and filling for rough grading. After that, crews install utilities and compact the subgrade. Finish grading follows, and crews perform the survey after the grading work is complete.

Design programs generate the grading model. Civil 3D program uses grading footprints, grading targets and grading groups. After that, the program transforms these groups into surfaces in order to compute volumes. Furthermore, field crews may use GPS grade control from machine-mounted systems to hit those surfaces.

As a result, efficient grading requires accurate input data. The table below describes the key inputs and their purposes.

Site Grading Safety and PPE

Grading exposes crews to heavy equipment and shifting soil. Therefore, safety begins with training. Train operators before they run bulldozers, excavators, or motor graders.

PPE protects workers against risks not controlled by other measures. The PPE standard as per OSHA regulation, 29 CFR 1926.95, states that PPE must be “provided, used, and maintained in a sanitary and reliable condition where necessary to protect workers.” Employers also must provide such equipment free of charge.

The hazard assessment process precisely determines the type of PPE needed for a site. Examples of such equipment include hard hats, high-visibility vests, eye protection gear, hearing protection near heavy equipment, gloves, and steel-toe boots. Workers should inspect PPE equipment daily and replace broken equipment.

Site habits also ensure compliance with safety regulations. Mark utility lines prior to making any cuts. Keep operators out of swing and travel paths. Finally, always have a signal person present during operations involving heavy equipment near crews. These precautions are essential for protecting your crew on any grading job.

Case Study: A Worked Grading Example

This is just an illustrative example of worked grading. It applies the Aurora slope limits to an imaginary commercial site. Thus, each of the numbers arises from the slope and the distance.

The parking bay at 150 feet must have enough fall in order to drain properly. The following table illustrates this:

Finally, the project requires fill under a 100-foot by 50-foot building pad. In this case, an elevation of 1 foot under such a pad will require 185 cubic yards of fill. Dividing 5,000 cubic feet by 27 gives this figure.

After that, the next step involves raising the pad 1 foot higher than the 100-year base flood elevation. At this point, the lowest elevation and the grass swales allow water to drain from the pad.

Conclusion

Good grading protects every construction project from water damage, weak foundations, and costly rework. Start early, survey the site, and develop a grading strategy before any equipment moves. Follow the plan’s steps and check each phase against design tolerances. Regular review keeps the schedule on track and the structure sound.

FAQs

How does rough grading differ from finish grading?

Rough grading establishes the overall elevation and slope in the preliminary phase of the construction process. On the other hand, finish grading attains the desired elevations for paving, foundations or plantings. Moreover, typical tolerances for finish grading are stricter compared to rough grading.

Why is final grading important for plant growth?

Final grading places topsoil that supports plant growth, seeding, and sodding. Otherwise, inadequate drainage may ruin landscaping.

What is the minimum slope for lawn?

According to Aurora, the minimum requirement for a lawn is 2.0%. Besides, according to Vista Projects, the minimum slope should be 2% away from the building foundation.

Who prepares the grading plan?

A civil engineer prepares the grading plan. Some areas require a licensed professional to seal it. For example, in Redmond, a Washington-licensed professional is required.

What is the importance of site grading?

Site grading creates a foundation, directs water runoff, and protects structural integrity. A sound construction grading strategy prevents flooding, settlement, and costly rework on every major project, large or small.

How are the cut and fill volumes computed?

Software compares existing and proposed surface profiles. The difference between them gives cut and fill volumes. Designers verify these totals before construction starts.

Why is site grading safety training important?

Site grading safety training teaches crews to run equipment safely. Personal protective equipment worn every shift keeps each crew safe with site work.

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