What is Chat Gravel? Using Decomposed Granite for a Patio

With more time spent outside this summer, you might be looking at your patio space and thinking it’s in need of a tune-up. And there are lots of ways to give your patio or outdoor space a transformation: fresh pavers, a new deck, or even stamped concrete. But many of those options can quickly become expensive, which might require you to skimp on other aspects of your planned makeover (or put it off until a later date).

If you’re itching to do a makeover on the cheap — and without waiting a year or longer — there’s an affordable patio material that should be on your radar: chat. “Chat” is the term for fine fragments of siliceous rock (sedimentary rocks that contain silica). These aren’t the recognizable rocks like granite or limestone — instead, they’re rocks you probably haven’t heard of, like chert and diatomite.

Ready to learn more about this secret ingredient to affordable patio transformations? I spoke with Rituparna Simlai, a landscape architect and founder of Studio Arth, an award-winning landscape architecture firm based in Miami, Florida, to get the details on all things chat — including what it is, where you can find it, and how to install it.

Just like gravel, chat is a natural material, says Simlai. “It is a unique material composed of fragments of sedimentary rock, primarily consisting of silicon dioxide in the form of silica or quartz,” she says. “It is often derived from limestone or dolomite waste that is left over from milling operations.”

During the mining and screening process, fine-washed sand and small coarse-grained gravel is produced. But what sets chat gravel apart, Simlai explains, is its distinctive composition, which includes a higher concentration of rock dust. This results in a variety of colors, with shades of brown being the most common, along with variations of gray and white with a brown tinge.

Chat is an attractive option for any walking paths or patio areas because it will naturally settle — meaning it will provide a more stable and comfortable walking surface, and is less likely to be kicked outside of its borders.

Simlai says that gravel is also known as decomposed granite, rock dust, crusher fines, disintegrated granite, or simply “chat.” These names are often used interchangeably to refer to the same material. 

Pea gravel, on the other hand, is a material very similar to chat, but is a substrate of small rocks that have been formed by natural weathering rather than the “dust” left over from production.

You can find chat at home centers, but if you want to use a lot of it, you might need to locate a supplier. Simlai recommends checking with local landscaping supply stores or construction material yards that offer chat gravel in bulk or by the ton, and be sure to consult with experts at the supplier or seek professional advice from a landscape designer to ensure accurate calculations for your project’s specific requirements.

The amount of gravel required for a patio can be calculated based on the area of use, multiplied by the desired depth. “It is recommended to consider a depth of 2 inches for home gardens, where approximately 90 to 100 square feet of area can be covered with 1 ton of chat gravel,” Simlai says. “Also, calculators are available online that allow you to estimate the amount of gravel required per square foot of land.” 

Chat gravel is inexpensive and easy to maintain with a wide range of usages in various outdoor applications, Simlai explains. “It is an elegant choice for driveways and walkways, providing a softer look without hard edges, allowing infiltration of rainwater, eliminating concerns about cracking in freeze-prone areas, and offering an alternative to traditional lawns that require mowing,” she says. “It is soft enough to place furniture or fire pits, or create a play area.” 

However, you’ll want to avoid using chat gravel close to the entrance of the house to prevent the fine dust from sticking to shoes and getting tracked inside. 

“Creative designs can be achieved by using chat gravel as a complete area coverage or as spacing between concrete pavers, with the gap size ranging from 4 inches to 1 to 2 feet based on functional and aesthetic preferences,” Simlai adds.

One of her favorite applications is designing a mortarless flagstone walkway with chat gravel infill, creating an appealing and low-maintenance outdoor pathway.

“When installing chat gravel, it’s crucial to level the ground and clear away any large rocks or debris, as well as de-weed the area thoroughly,” Simlai advises. “Digging 6 to 8 inches below the desired finished level of gravel is recommended.” 

To define the boundary and keep the gravel in place, she recommends DIYers use a plastic or metal landscape edge. This edge not only provides a clean look, but also helps prevent washouts during rain. 

Additionally, a weed barrier is essential to minimize weed growth. Stretch the barrier and pin it securely to the ground, add heaps of gravel, and then use a rake to level it out. 

Finally, compact the gravel with a hand tamper for a stable surface. For driveways, consider using gravel pavers or gravel grid stabilizers for additional stability. 

“We don’t advocate using binding solutions like cement, as this makes the gravel non-permeable and prevents water infiltration,” Simlai says. “This ultimately interferes with the soil ecosystem, and makes the design unsustainable.”