Gravel grid installation can be time-consuming and labor-intensive, so it’s important to purchase a product that can withstand the test of time. So how do you determine which product to use? We offer guidance in this article.
This is the third article in a three-part series about gravel grids:
- “What are Gravel Grids?”
- “What are the Pros and Cons of Gravel Grids?”
- “How Do I Pick a Gravel Grid Product?” (this article)
Choose a Product Style that Meets Your Needs
As discussed in our previous article, gravel grids come in three distinct styles:
- Paver tiles
- Rolled mats
- Collapsible panels
Check out “What are Gravel Grids?” for pictures of gravel grid styles.
Paver tiles and collapsible mats are laid out and snapped, stapled, or clipped together. Collapsible panels must be expanded and staked in place.
Some paver-style and rolled mat-style gravel grids can be driven on while empty, which could make filling the cells easier. Collapsible panels aren’t fully supported until filled with gravel.
Make Sure the Specifications Meet Your Project Needs
To make sure your gravel grid system performs as promised, check the specifications or data sheet for the product. Make sure the data supports how you will use the product. For example, if you plan to drive on the gravel grids, make sure the load-bearing capacity (the compressive strength when filled) is up to par. Products that are pushed beyond their limits can buckle, warp, blister, break, and/or pull up.
Manufacturers should be transparent about their data and share it on their website. Take special note of brands that took the extra step of being independently tested based on AASHTO and ASTM standards (important standards followed throughout the U.S.).
Below we discuss common specifications and qualities to look for.
This refers to the compressive strength of the gravel grid when it’s empty. It measures the amount of force it takes to break the product. This measurement is typically in pounds per square inch (psi), tons per square meter (t/m²), or pounds per square foot (lbs/ft²).
None of the collapsible panel-style gravel grids we researched listed this rating. A rep for one of these brands said crush resistance and load-bearing capacity aren’t relevant to this style of product because it relies on the base gravel and infill gravel for support. Other measurements like seam strength and tensile strength are more important to determine the quality of a collapsible panel-style gravel grid.
This refers to the compressive strength of the gravel grid when it’s filled with gravel. It measures the amount of force it takes to break the gravel grid when it’s filled with gravel. This measurement is typically in pounds per square inch (PSI), tons per square meter (t/m²), or pounds per square foot (lbs/ft²). High compressive ratings are most important for heavy-duty applications like driveways and parking lots.
Some product literature will say “exceeds HL-93,” “exceeds H-20,” or “exceeds HS-20.” This refers to design-load ratings, or the maximum amount of weight that the wheels or axles of a truck can safely support. HL-93 is equivalent to H-20 and HS-20 standards. An H-20 and HS-20 load rating means that a product can handle heavy-duty traffic, or up to 16,000 pounds per wheel load or 32,000 pounds per truck axle.
The chart below compares compressive strength ratings across brands.
Some dealers argued that compressive strength isn’t the most important factor in determining the quality of a product. In fact, GeoPave’s marketing materials urge customers to “avoid specifications that state material compressive strength only. Material compressive strength, with applied factors of safety must be sufficient to resist compressive and lateral loads. In addition, ultra-high compressive strength adds little value to a porous pavement system [emphases added].”
In other words, heavy-duty paved surfaces should be able to accommodate many types of stress, such as vehicles turning, vehicles braking, snowplowing, etc. Customers looking for a high-quality, heavy-duty gravel grid product can refer to other measurements, like tensile strength.
This refers to a material’s ability to withstand the effects of ultraviolet light, which degrades and weakens plastics over time. Note whether a product is made with a UV stabilizer or light absorber.
Chemical Resistance (Solubility)
This refers to the plastic’s resistance to chemicals. Look for gravel grid products that are resistant to deterioration via water, acids, alkalis, alcohols, petroleum products (oil, diesel, gasoline), salt, ammonia, etc.
This refers to a product’s resistance to heat and cold. Gravel grid products should resist cracking or deforming due to temperature changes. Some gravel grids will list a temperature range that their product can withstand. You can also look for terms like “frostproof” and “weatherproof” and references to freeze-thaw cycles.
Some manufacturers may refer to a product’s dimensional stability. According to the Ensinger Plastics company, dimensional stability refers to “the ability of polymers to maintain their size, even under varying environmental conditions. As a result, a dimensionally stable plastic shows low water absorption with low thermal expansion.”
Many gravel grid products are made from recycled or recyclable plastics. If environmental factors are important to you, look for terms like “inert,” “ground water neutral,” etc.
Some brands also claim their systems can filter pollutants from water, which may be a quality of interest.
If permeability is important to you, look for information about water infiltration rate and void ratio. The water infiltration rate refers to how quickly water passes through the gravel. The void ratio refers to how much space exists around the gravel in which to store water.
Permeability is just as much about the gravel you use as it is about the design of the gravel grid. So make sure you follow the manufacturer’s instructions if permeability is the goal.
Note Special Certifications or Qualifications
Some gravel grids take the extra step of meeting special requirements. Here are a few qualifications to note:
- ADA compliant: meets standards for accessibility set by the Americans with Disabilities Act (ADA)
- SUDS-compliant: meets a UK permeability standard for Sustainable Urban Drainage Systems (SUDS)
- LEED-certified: meets a sustainability design standard; the LEED certification point system ranges from Certified at the lowest end to Platinum at the highest end
Check the Installation Guide to Determine Additional Costs and Requirements
Look at the manufacturer’s installation guide to calculate the true cost of the product, including gravel, geotextiles, equipment, and accessories like stakes and clips. Refer to our previous article for a spreadsheet comparing material requirements across brands.
Here are some considerations to watch out for in the instructions:
- Is a geotextile recommended between the subgrade and base layer of gravel (or between the base layer and the gravel grid)?
- How high does the base layer of gravel have to be? See our guide for instructions on how to calculate the volume of gravel you will need.
- How tall are the walls of the gravel grid (i.e., how much gravel infill is needed)?
- What kinds of gravel are required for the base layer and infill layer for the system to be permeable?
- Do separate panels or paver tiles need to be attached together with clips or staples?
- Does the product need to be staked in place on level and/or sloped areas?
- Does the manufacturer require clips, stakes, etc. that are a special design only offered by the manufacturer?
- Is special equipment required, like plate compactors?
- Are transportation and tax included in the cost of the gravel grid?
Determine if Hiring a Contractor is Necessary
Residential customers may be able to handle smaller projects, like pathways or patios, on their own. An EcoPave dealer recommended contracting out large projects like driveways. A contractor can deal with the more complicated details of a project, like permitting issues, subgrade issues, excavation, and gravel specifications.
Consider Added Value, Like Customer Support and Design Assistance
An EcoPave dealer told us that many manufacturers will make big claims, “but if you ask questions or need design assistance, they’re just absent in that conversation.”
EcoPave offers design assistance and customer support through dealers. Dealers for products like TrueGrid, EcoRaster, and GeoPave welcomed questions and offered extensive informational materials. If customer assistance is important to you, use the contact information on the brand’s website to reach out and ask questions.
Compare Dealer Prices to Big Box Stores and Online Retailers
We found in one case that buying through a dealer was actually cheaper than buying through Amazon because the dealer orders large quantities of material for commercial clients. It may be worth your time to get estimates from more than one company. Don’t forget to compare transportation costs.
This article does not represent an endorsement of any brand and is meant for educational purposes only. There is a possibility of errors in the data. If you notice any errors, please send us a note through our contact form.
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