By Paul Bianchina
For driveways, paths, parking areas, utility areas, weed and fire control and a variety of other uses, crushed rock can be an ideal solution. It's durable, virtually maintenance free, reasonably priced, and available in a variety of colors and sizes for different applications.
While just about any crushed rock can be used for just about any application, some rocks are better choices then others for certain uses. For example, some rock packs down better than others, making it a better choice for roads. Others are smooth and rounded, and while they don't pack as well, they're softer underfoot and may be a better choice for some walkways and dog runs. You'll also find some regional differences as well - some areas may carry more river rock than others, or more lava rock or different grades and sizes of crushed rock.
Some of the more common rocks and their applications include:
River Rock
River rocks are rounded and smooth in appearance, with no sharp or pointed edges. Their rounded shape causes them to roll slightly underfoot and they don't pack down hard against one another, but they drain water very well and are more attractive than some other types of crushed rock. Common size ranges, which indicate the average diameter of the rock, include 3/8 inch-1/2 inch, also called pea gravel; 1/2 inch-1 inch; and 1 1/2 inch-2 1/2 inch. Larger sizes are also available.
Common uses include paths, landscaping, and drainage areas. River rock is also sometimes used for animal areas and driveways. Pea gravel is a common additive in decorative exposed aggregate concrete, and the larger river rock is common for use in septic drain fields.
Crushed Gray Rock
This is the generic "gravel" and is more sharp and irregular on the edges. The sharper edges cause the individual pieces to interlock with one another, packing them down more firmly underfoot. The two common sizes include 0-3/4 inch, called "3/4 minus," which has rocks ranging from 3/4 inch down to powder. The powder, called "fines," fills in all the little areas between the larger rocks for good compaction, although it can be dusty to drive on until it gets a sufficient amount of water to settle everything into place. The other size is 1/4 inch-3/4 inch, which packs just about as well without as much dust, although the packing may take a little longer to occur. Common uses for both materials include roads, driveways, base rock for asphalt and concrete slabs and paths and walkways.
Cinder
Volcanic cinder, which may not be available in all areas, is light, porous, and moderately irregular, allowing for fairly good packing and very good drainage. The rocks will crush down further with repeated use, which improves the hardness of the pack but requires additional layers to be added periodically in order to maintain the desired thickness. Common sizes include 0-3/4 inch and 3/4 inch-1 1/4 inch, and both red and black cinders are available. Common uses include driveways, paths and landscaping.
How Rock is Sold
All types of crushed rock is sold by the cubic yard, which is equal to an area 3 feet wide by 3 feet long by 3 feet high. One cubic yard is also equal to 27 cubic feet. As a general rule of thumb for calculating your coverage needs, you can figure that one cubic yard will cover: 160 square feet at 2 inches deep, 108 square feet at 3 inches deep, 80 square feet at 4 inches deep, 54 square feet at 6 inches deep.
You can haul the rock yourself if desired - the dealer will load it for you - or you can have your dealer deliver it for a nominal cost, which is usually waived if you buy a large enough quantity at one time. If your site is accessible, most dealers will also drop the rock off the truck so that it spreads out, rather than just dumping it in a pile - something that can save you a considerable amount of shoveling and spreading by hand.
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