Fine Grading: What Is It and Why Is It Important

Fine grading, sometimes referred to as “finish” or “final” grading, is an essential step toward high-quality, long-lasting construction projects.

Fine grading is the process of shaping and leveling the gravel base material to ensure it meets the required slopes and elevations, prior to the asphalt paving itself.  This is a pivotal step which ensures that final asphalt surface drains properly.  When asphalt paving drains adequately, the durability and longevity of its life cycle increases significantly.

In a new construction scenario, the fine grading is completed after rough grading; the first shaping of the site. In a asphalt removal and replacement scenario, the fine grading takes place after the existing surface asphalt has been removed and discarded from site.  

What are the goals of well executed fine grading?

The primary goal of fine grading is to produce strong, level, template for the asphalt paving equipment to pave in a way that will provide effective site drainage. Fine grading and base prep is an incredibly important step of the paving process for the following reasons:

Drainage: Well executed fine grading ensures water flows to drainage swales and/or catch basins and prevents pooling in undesirable areas. Poor drainage can cause several hazards, from slip and falls in winter months to water damages such as erosion, which in time causes cracking, undesired settlement leading to pot holes, etc.

Smooth Asphalt Surface: Once the fine grading process is complete, the asphalt paving equipment runs directly on the graded gravel surface. It is very important that the gravel base is not only strong, but also smooth to allow for uniform asphalt depth and smooth surface finish. Uneven or soft base granular often lead to issues such as pot holes, cracks, or even structural failure.

Surface Stability: Fine grading ensures that the gravel base is strong, level, and consistent. This provides a stable foundation for the asphalt paving and/or concrete to be installed. 

Fine Grading Best Practices

As we now know, fine grading is a pivotal process of asphalt paving. To ensure the fine grading is completed correctly, here are several considerations and recommendations we recommend during this process:

Use Proper Equipment: Fine grading requires specialized equipment. Skid steers, graders, hand tools and vibratory compactors are the most common pieces of equipment for the fine grading process. In areas of very low slope, sub 1% grade for instance, gps or laser guided grading box attachments with mount to skid steers can be incredibly useful to achieve precise grading requirements.

Pre-Grading Site Review: Before starting fine grading for remove and replace paving projects, we recommend reviewing the existing site to analyze if there are any existing ponding or grading issues prior to asphalt removals. This step will allow us to plan ahead, and potentially revise the existing grades to achieve better overall drainage post construction. 

Controlling Moisture Content of the Gravel: Moisture content of the base material is critical during the fine grading process. If the base gravel is too wet, it becomes unstable, and can lead to ruts and mud while attempting to grade. If the base is too dry, and the gravel may not compact properly. It is very important to maintain proper moisture levels to optimize compaction and stability during fine grading. 

Give it Time: If the gravel base is very soft due to ground water levels, giving the base time to dry out naturally can do wonders for firmness and stability of your property. We use this ‘trick’ often on projects where budgets do not allow for urgent removal and replacement of soft granular. Excavating to remove soft base material can be incredibly expensive, and in certain cases can be avoided by leaving the base exposed to summer heat and sunshine. 

Utilizing Water/Rain: Utilizing water sprinklers or rain can help compact the gravel and create an incredible strong, stable base. Of course, as noted above, its important to not over do it herem as adding or exposing too much water can also be counterintuitive. 

Layered Gravel Install: Its important to not install new gravel layer too deep. Rule of thumb is to install gravel in lifts of 6″ at a time to allow for adequate compaction of each layer. Many granular specifications call for larger stone in the deeper sub-base, finished with a finer gravel top to allow for more precise fine grades.