By Steven Brahney | February 27, 2024



The Importance of Subgrade Inspection Before Asphalt Paving: Avoiding Costly Mistakes


IMG_2050As an asphalt paving expert dedicated to delivering quality services to commercial property owners and property managers, I understand the critical role that subgrade inspection plays in the success of any paving project. In this blog post, I aim to shed light on why it is crucial to inspect the subgrade under an asphalt parking lot before milling and paving to avoid costly change orders and ensure long-lasting results.

Picture this scenario: A property owner is approached by a paving contractor promising quick and affordable paving services for their parking lot. Eager to enhance the property's aesthetics and functionality, the owner agrees without fully understanding the importance of a thorough subgrade inspection. The contractor, focused on quick completion and profitability, skips the crucial step of assessing the subgrade and addressing underlying issues.

Paving over a non-load-bearing subgrade or neglecting underground water issues can lead to a host of problems that compromise the integrity of the parking lot. One of the major issues that arise from insufficient subgrade inspection is the risk of structural failure. Without a strong and stable subgrade to support the asphalt surface, the parking lot is prone to cracking, rutting, and premature deterioration.


Furthermore, paving over non-load-bearing subgrade can result in uneven surfaces, poor drainage, and increased maintenance costs in the long run. Water pooling and drainage problems become common, leading to safety hazards and liability concerns for property owners. Inadequate subgrade preparation also undermines the durability and lifespan of the asphalt pavement, requiring frequent repairs and replacements.












Watch the video above to see how a property owner spent over $500,000.00 on a paving project without the paving contractor inspecting the subgrade and the issues it left behind.  


IMG_0364Now, let's delve into the story of another property owner who fell victim to a hasty paving decision without proper subgrade inspection. A paving contractor convinced the owner to proceed with the project quickly, assuring them that all necessary steps would be taken to ensure a smooth paving process. However, due to the lack of subgrade inspection and corrective measures, the newly paved parking lot started showing signs of distress within months.

Cracks began to form, water accumulated in puddles after rain, and the surface became uneven and unsafe for vehicles and pedestrians. The property owner, initially impressed by the speedy completion, now faced the consequences of a poorly executed paving job. The contractor, eager to move on to the next project, was nowhere to be found when the property owner sought assistance to rectify the subpar work.

In conclusion, the lesson to be learned from this cautionary tale is clear: rushing into paving projects without proper subgrade inspection is a recipe for disaster. Commercial property owners and managers must prioritize thorough subgrade evaluation to identify and address potential issues before milling and paving. By investing time and resources in subgrade inspection, property owners can avoid costly change orders, ensure the longevity of their parking lot, and maintain a professional and safe environment for tenants and visitors.

Remember, a solid foundation is the key to a successful paving project. Don't let the allure of quick fixes and shortcuts lead to a paving nightmare. Take the time to inspect the subgrade, address underlying issues, and partner with reputable paving experts who prioritize quality and sustainability in every project. Your parking lot and your investment deserve nothing less.

















Selecting a Paving Contractor Who Prioritizes Sub-Grade and Drainage Inspection


Choosing the right paving contractor is a critical decision that directly impacts the longevity and effectiveness of your asphalt paving project. A reputable contractor understands the importance of thoroughly inspecting the subgrade and drainage systems before submitting a proposal. This step is essential for identifying any underlying issues that could compromise the integrity of the new pavement. A contractor who takes the time to evaluate the sub-grade condition and assess drainage needs demonstrates a commitment to quality and durability. This approach ensures that any potential problems are addressed before paving begins, paving the way for a smoother, more durable asphalt surface that stands the test of time. When selecting a paving contractor, prioritize those who emphasize the importance of pre-paving inspections and who are willing to discuss their findings and recommendations openly, ensuring your project is built on a solid foundation from the ground up.


When a commercial paving contractor undertakes the task of inspecting the subgrade and checking for underground water issues before paving a parking lot, several essential steps are involved to ensure a thorough assessment and proper preparation. Here is an overview of the typical process that a reputable contractor would follow:

1. Site Visit and Evaluation:

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   - The contractor starts by visiting the commercial property to assess the existing condition of the parking lot and surrounding areas.
   - They evaluate the surface of the parking lot for any visible signs of distress such as cracks, potholes, rutting, or uneven areas that may indicate underlying subgrade issues.

2. Subgrade Inspection:

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   - The contractor conducts a detailed inspection of the subgrade beneath the existing asphalt surface.

   - This involves testing the soil quality, compaction, and stability of the subgrade to determine its load-bearing capacity and suitability for paving.  -

*** Does the contractor understand the geology of the area the parking lot is constructed upon?

3. Asphalt & Sub-Grade Coring:

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   - In some cases, the contractor may perform coring equipment specialized equipment to assess the soil composition, asphalt thickness, sub-base thickness, and identify any potential weak spots or areas of concern.
   - This testing helps in determining the depth and condition of the subgrade and detecting any underground water issues that could impact the paving process.

4. Water Drainage Assessment:

   - The contractor evaluates the water drainage system in and around the parking lot to ensure proper water runoff and prevent water accumulation on the surface.
   - They check for signs of standing water, ponding, or water seepage that could indicate underground water issues affecting the subgrade.

5. Underground Water Detection:

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   - Using visual inspection, the contractor may detect underground water sources or pathways that could lead to water surfacing through the subgrade.
   - This step is crucial in identifying potential water infiltration points that need to be addressed before paving to prevent future drainage problems and pavement failure.

6. Analysis and Recommendations:
   - Based on the findings from the subgrade inspection and water assessment, the contractor analyzes the data to determine the necessary corrective actions and recommendations.
   - They provide detailed feedback to the commercial property owner or manager, outlining the issues identified, proposed solutions, and the importance of addressing them before proceeding with the paving project.


The Essential Investment: Costs of Drainage and Sub-Grade Inspection for Asphalt Parking Lots.  What Is The Average Cost?

Before embarking on an asphalt paving project for your parking lot, understanding the foundational steps—and their costs—is crucial for ensuring long-term durability and functionality. Among these preliminary steps, drainage and sub-grade inspections stand out as critical components that can significantly influence the success of the project. This blog article delves into the importance of these inspections and provides insights into the associated costs, offering property owners a comprehensive overview to aid in budgeting and contractor selection.

The Importance of Drainage and Sub-Grade Inspections

A parking lot’s longevity and performance are deeply rooted in its foundation. The subgrade—the soil layer beneath the pavement—must be properly prepared to support the asphalt above. Similarly, an efficient drainage system is paramount to prevent water accumulation that could lead to asphalt deterioration over time. These inspections not only identify potential issues that could undermine the pavement's integrity but also guide the necessary preparatory work to mitigate such risks.


Understanding the Costs


Drainage Inspection

The cost of a drainage inspection can vary based on the parking lot's size, the complexity of the existing drainage system, and the geographic location. On average, property owners can expect to pay between $500 to $2,500 for a comprehensive drainage evaluation. This inspection might include assessing catch basins, pipes, and surface grading to ensure water is effectively directed away from the pavement area.  Most asphalt paving contractors will agree to credit this fee back to a project if they are awarded the contract to perform the work.

Sub-Grade Inspection

Sub-grade inspection costs are influenced by the lot's size, the terrain's complexity, and the depth of the inspection required. Prices can range from $500 to $3,500. This process may involve soil testing to determine the soil type, compaction levels, and the presence of any materials that could impede proper drainage or lead to uneven settling.  Most asphalt paving contractors will agree to credit this fee back to a project if they are awarded the contract to perform the work.

Bundle and Save

Some contractors may offer bundled inspection packages that include both drainage and sub-grade assessments. Opting for a combined service can often result in cost savings, with packages potentially ranging from $700 to $3,500, depending on the scope and depth of the inspections needed.  As stated previously, most paving contractors will credit this fee back.  

The Return on Investment

While the initial outlay for these inspections might seem substantial, the return on investment cannot be overstated. Identifying and rectifying subgrade and drainage issues before paving can save property owners significant expenses in repairs and premature pavement failures. Moreover, a well-prepared foundation and efficient drainage system extend the asphalt's lifespan, enhance safety, and improve the property's overall value.

Selecting the Right Contractor

Choosing a contractor who understands the importance of thorough pre-paving inspections is crucial. A reputable contractor will not only offer these services but will also provide detailed explanations of the findings and recommend the best course of action. When selecting a contractor, inquire about their experience with drainage and sub-grade inspections and ask for references from previous projects.


Investing in drainage and sub-grade inspections before beginning asphalt paving work on your parking lot is a wise decision. These preliminary steps are essential for identifying and addressing potential issues that could affect the pavement's integrity and lifespan. By understanding the associated costs and the value they bring, property owners can better budget for their paving projects and choose contractors who prioritize the long-term success of their investment.

By following these systematic steps and conducting a comprehensive inspection of the subgrade and underground water conditions, a professional paving contractor ensures that the paving process is built on a strong foundation. Prioritizing subgrade evaluation and addressing water issues proactively not only prevents costly change orders during paving but also enhances the longevity and performance of the parking lot.

If you are considering a paving project for your commercial property, make sure to partner with a contractor who values thorough subgrade inspection and prioritizes quality craftsmanship. By investing in a meticulous assessment of the subgrade and addressing underground water concerns upfront, you can avoid potential paving pitfalls and enjoy a durable and well-maintained parking lot for years to come.

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