You can choose to purchase a discounted ground tarp for only $10. The regular price is $39. It is not absolutely necessary though. It simply makes it easier to keep the bottom of your tent clean if you are camping in a dirty or muddy area you don't have to wipe off the bottom of your tent. Instead, he let the tarp dry out and shake it off. Some customers also use it inside the tent if they are in a sandy area and they don't want to sweep out the tent after they are done. The floor included is already very heavy duty, but the ground tarp provides a little bit off added protection if you know you will be in an exceptionally rocky camp site.