When planning your DIY project and need information about gravel, here is a simple breakdown of gravel types and uses. The information offered is for product we crushed and screened in the Magic Valley located in southern Idaho. Aggregate differs from region to region, so this information is a guide and not absolute.
Driveway gravel is produced in different types and looks. Choose crushed gravel (a minimum of 80% fracture on two faces, and a maximum of 8% -#200 or fines) as it will lock together, reducing the amount of movement. Ask your supplier for the spec sheet (sieve analysis) on the gravel you selected. If building a driveway from scratch, elevation plays a role in what to do. The water will shed at minimum 2% slope so crown your driveway and slope the parking areas for water to drain. Standing water will soak in and saturate your gravel and base, losing stability.
Depending on your project, the size of gravel will vary. To build a base for a new driveway, you will need to determine what type of traffic and loads will be using your driveway. For heavy semi truck use, a base layer of 6” of 1” to 1 ½” fractured rock (no fines in this product) was a common practice with a 4” cap of 1 ½”- (with fines). The base layer of rock will need to be compacted before the cap of gravel is placed. The cap needs to be compacted also. This may seem extreme for most homeowners, but not properly building a driveway in the beginning will only cost more later on. The gravel will disappear, going down to seek bearing if it is not properly built and sloped. A skim coat of gravel will not hold up even light vehicles. Most people will not have the necessary equipment to build a driveway, so this is to inform a homeowner what they should look for when receiving bids to do this type of work.
Another option is excavating out some of the topsoil to enable construction of projects and driveways. Topsoil is expensive and most homeowners keep it on site to complete landscaping projects and garden areas. Topsoil has less stability than subsoil so excavating the topsoil to have better stability and achieve desired elevations is common.
For small jobs such as a concrete pad, generally a minimum of 4” of gravel is good in most cases. Types of gravel used can be a ¾“minus, compactible fines, or any clean compactable product. The gravel provides some drainage under the slab. Your concrete requires slope also for water to drain.
To lay pavers for a driveway use the same cross section as normal driveway requirements. To build a paver patio or sidewalk, a minimum of 2-3 inches of a compactable product would probably suffice.
All the information stated here if not a guarantee but a guideline for projects. Soils and aggregates vary; climate differences and other factors may require different methods than what has worked for us in our location. It is best to consult a reputable construction company and secure written bids for your area. If you are a diehard DIY, go to your local gravel producer and have them show you what is available.
Being in the gravel business for a lifetime, we have seen a person hire someone who has no idea what is required and when foul weather arrives they are in our office spending additional money to correct improper construction of their driveway. Their cars get stuck and they cannot get to their homes. If built correctly the first time, it is money well spent.