What Is Chat Gravel and Should You Use It?
Explore chat gravel, a low-cost aggregate known for its excellent compaction. Understand its full profile to determine if it's a suitable choice for your project.
Chat gravel is a surfacing material known by several names, including chert gravel, decomposed granite, or crusher fines. It is popular for functional and decorative projects, such as building driveways and garden pathways. The material is valued for its unique properties and relatively low cost, offering an alternative to more common options like asphalt or pea gravel.
Understanding Chat Gravel
Chat is a type of gravel defined by its geological origin and physical properties. It is primarily composed of chert, a hard, fine-grained sedimentary rock made of microcrystalline quartz that gives the material its durability. The rock is often sourced as a byproduct of mining operations, particularly from lead and zinc mines.
Chat gravel consists of small, angular particles, with individual pieces around 1/4 inch to 3/8 inch in diameter, though sizes can vary. This angularity allows the particles to interlock and compact tightly, creating a firm and stable surface. The color of chat gravel varies depending on its mineral content and source, but it commonly appears in shades of gray, brown, and tan.
Common Applications
For driveways, chat forms a durable surface that resists rutting and displacement from vehicle traffic. For walkways, garden paths, and patios, it compacts to create a firm surface that is more solid underfoot than rounded pea gravel. Its fine texture provides a relatively smooth walking area.
It can also be used as an infill material between pavers or flagstones, creating a low-maintenance and visually appealing design. Chat also serves as an effective base material, providing a stable and well-draining foundation for concrete slabs or pavers.
Advantages and Disadvantages
One of the most significant advantages of chat gravel is its cost-effectiveness, often being considerably cheaper than decorative gravels, concrete, or asphalt. Its excellent compaction creates a stable surface that is less prone to scattering, making it suitable for sloped areas where erosion control is a concern. The material’s permeability is another benefit, as it allows for natural water drainage.
However, the sharp, angular texture of chat is not comfortable for bare feet and can be harsh on the paws of pets. Its plain, functional appearance may not suit all aesthetic preferences, as it lacks the decorative quality of other stones. When dry, chat can also produce fine dust that may be tracked indoors.
Health and Environmental Considerations
A primary concern with chat gravel is its potential to contain heavy metals, a legacy of its origin as a mining byproduct. Chat sourced from historic lead and zinc mining regions can contain traces of lead and cadmium. Exposure to these metals can pose health risks, so it is advisable to inquire about the source of the material before purchasing.
Another health consideration is the risk of silicosis, a lung disease caused by inhaling fine crystalline silica dust. This dust can become airborne during installation, especially when the material is dry or in windy conditions. Wearing a dust mask during installation can significantly reduce the inhalation of these fine particles.
To mitigate these risks, sourcing “washed chat” is a good practice, as the washing process removes much of the fine dust and potential surface contaminants. Wetting the material down before spreading it can also help control dust.
Installation Guide
The first step is site preparation, which involves clearing all vegetation, rocks, and debris from the designated area. The site should then be excavated to the desired depth, between 4 and 8 inches, and graded with a slight slope of 1-2% to ensure proper water drainage.
Before laying the gravel, you must calculate the required volume by multiplying the area’s length, width, and depth. After excavation, laying down a high-quality, water-permeable landscape fabric is recommended. This barrier prevents weeds from growing through the gravel while still allowing water to drain into the soil below.
With the barrier in place, spread the chat evenly with a rake to a depth of 3 to 4 inches. For the final step, compact the gravel with a plate compactor or a heavy roller. This process locks the angular stones together, creating a solid and stable surface.
Cost and Sourcing
Chat gravel is sold by the ton or the cubic yard, with bulk purchases being more economical. On average, you can expect prices to range from $15 to $75 per ton, depending on the region and specific type of chat.
The final cost will also be influenced by delivery fees, which depend on the distance from the supplier to your location. Another factor is whether the chat is “washed” or “unwashed.” Washed chat, which has had fine dust and silt removed, costs more but is often preferred for reducing dust and potential contaminants.
You can find chat gravel at landscape supply yards, quarries, and sand and gravel companies. A reputable supplier should be able to provide information on the source and composition of their product.