The short answer, just lava rock.
Upon reading our installation guides, you will see sand as an optional medium to use over the top of lava rock in order to create a bed for the glass to sit on. We used to use sand in most installations. We have moved from that position to recommending the use of lava rock (or pea gravel) only. Consider the following:
- For a fire pit, the lava rock can be brought up until it is level with the ring burner. There will be no chance of the gas flow being blocked once the sand gets damp from rain.
- When the lava rock or pea gravel size is around 1/4 inch, the glass will rest on top of it and won’t trickle down and get mixed with the lava rock.
- Not using sand simplifies the installation process by removing one step.
- For fireplaces, you need not worry about finding dry sand to use, as sometimes the sand is damp when you purchase it.
- Natural gas will flow through the crushed lava rock better than it will flow through dry sand. It will have a very hard time flowing through wet sand.
- There is no concern of crushed lava rock settling/sinking in a fire pit as there is with sand.
Hopefully, this clears up some misunderstandings of the use of sand as your base fill in fire pits or fireplaces. Feel free to bring on the questions.