Now that you’ve decided to install a crushed stone driveway, it’s time to do some research and pick the best material for your project. There are many types of crushed stone, making the decision making process that much more difficult. With the proper research, you’ll be able to get familiar with the pros and cons of each type.
The Layers of a Crushed Stone Driveway
Before looking at the different types and sizes of crushed stone, it is important to understand what a driveway made of this material consists of:
- A driveway bed of 6 to 12 inches deep, the base of which has been compacted.
- Three layers of crushed stone, each about 4 inches thick.
- The first and bottom layer will consist of the biggest size stone, the next will be smaller, and the last will be a combination of stone and coarse dust.
Types of Crushed Stone
Crushed stone is typically produced from traprock, sandstone, limestone, or granite. Large pieces of rock are run through a crusher, one or more times, and graded by mesh screens into different sizes. Fine stone, fines or screenings, which are the consistency of coarse powder, are also yielded during this process.
Crushed stone comes in a large variety of colors, as it depends where your supplier is sourcing the stone from and what type of rock it is. A reputable crushed stone producer will be aware of the environmental impact of quarrying stone, and will be dedicated to making sure that the land is later reclaimed for alternative uses.
When the stone is crushed, it has rough edges and surfaces that create friction when a vehicle is driven over it, making it one of the ideal materials for driveways. In addition, crushed stone driveways are natural and rustic in appearance, and come at a reasonable cost.
Sizes of Crushed Stone
There are many sizes of crushed stone available, usually from 1/4 inch up to 2 1/2 inch. In between, you get 3/8 inch, 5/8 inch, 3/4 inch; these sizes are all suitable for driveway construction.
You may also see a minus size listed, for example, 1/4 inch minus. This means that you will be buying stones up to a quarter of an inch in diameter that are mixed together with fines and stones up to that size. Stone that falls into a minus specification is best for the top layer of a crushed stone driveway as it creates a stable layer that does not easily shift about.
The American Society for Testing and Materials (ASTM) has a numbering system that classifies crushed stone according to its size. The most common sizes used in driveway construction are #2 and #57. The #2 is about 2 1/2 inches in diameter, and the #57 is about 3/4 inch to 1 inch.
Any of these sizes of crushed stone may come as clear, clean or washed stone. This just means that there is no fine stone mixed in with it. This type of stone is ideal for lower levels of driveways as it lets the rainwater run freely through it and it creates a firm base.
Also used for driveways is Dense Graded Aggregate (DGA), also known as crush and run or crusher run. This is a mixture of small crushed stone and stone powder.
There are fairly firm guidelines for the best sized stone to use for a crushed stone driveway. However, the colors and landscape design you choose are a matter of personal taste, so you can make your crushed stone driveway fit in well with the style of your house and garden. Consult with your stone producer company to get the best materials for your driveway.