Flooring is an important part of every house or a room, so, it is an important part of a green shack as well. Basically, you can use only cheap and easy to install floorings. As you may assume, laminate flooring isn’t an option. It cannot sustain moisture and water. If it is exposed to water too much it will start cracking, the best alternative you can choose is simple hardwood flooring. Just remember to raise it from the ground. A few inches are enough. You are doing this in order to reduce the contact with moisture and water. The good side is that you can do it yourself. There is no need for professional. After you install it, paint it. A paint for wood will protect it and save it from the water and damages.
If you want to use rugs or carpets, forget it. They also must avoid contact with water. When exposed, they will start to smell. That smell is so strong and repelling that you cannot stay in the green Shack. The same situation is with rugs. But you can throw them out easier than a big carpet.
Concrete is an interesting option. You can use it, but you cannot remove it. I mean you can, but it will require a lot of work and you will have to break it into small pieces in order to remove it. Some people don’t pay attention to the flooring in their green Shack. The thing is, you can also do the same. There is no some real need for it, but it will be much more pleasant if you have some adequate flooring.