Sub-base is the term used to describe the material that lies directly underneath the artificial grass surface. There are a couple of sub-base varieties used in artificial grass installations. Each has its own strength and specialty.
Crushed Miscellaneous Base
This sub-base typically comes from recycled concrete or recycled asphalt. It consists of a sand-gravel mixture of varying-sized particles up to ¾ of an inch in size.
CMB compacts better and is less expensive than decomposed granite, which is why it is the more common choice for landscaping applications.
Often referred to as DG, this sub-base is granite rock that has weathered to the point that it readily fractures into smaller particles of gravel, sand, and clay.
DG is more permeable and can be used to achieve a smoother finish than CMB, but it is substantially more expensive. DG is more suited for putting green applications.
So which is best?
Both are great materials for your sub-base. CMB is more easily compacted than DG but doesn’t drain quite as well. DG, meanwhile, yields a smoother finish than CMB but it is quite a bit more expensive. Generally, CMB is the best choice for artificial grass in landscaping while DG is the best choice if you’re installing a putting green.
After you’ve spread the sub-base material over your installation site, your best option for a proper installation is to use a vibratory-plate compactor. You may also opt to use a roller and a hand tamper to get those hard-to-reach areas and tight corners. And be sure to wet down your sub-base as you’re compacting it to help remove any voids or air spaces.