The solution for preventing this is to replace the soil with a substance that will not expand or contract. A proper sub-base comprised of either class II road base (also known as crushed miscellaneous base or CMB) or decomposed granite will provide an excellent foundation for your artificial grass and will help ensure you get the most out of your investment.
CMB vs DG
CMB is a blend of recycled concrete and/or recycled asphalt and consists of a sand-gravel mixture of varying-sized particles up to ¾ of an inch in size. Decomposed granite, or DG, is granite rock that has weathered to the point that it readily fractures into smaller pieces of weak rock and/or into mixtures of gravel, sand, and silt-size particles of clay. 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.
Sub-base Compacting
Once you’ve decided on the appropriate sub-base material, it’s time to shake a leg…and everything else too! 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. Oh, and be sure to wet down your sub-base as you’re compacting it to help remove any voids or air spaces.
