Building a shed floor is the first step if you want to make a shed by yourself, but it has an essential role for the durability of your project. therefore, we recommend you to work with attention and to adjust the size of floor to your needs.. Level the ground (if necessary) and install deck piers along a grid to support the shed. the piers will allow you to string support beams beneath the floor of the shed. in the example design, the piers are spaced 6 feet (1.8 m) apart in one direction and 4 feet (1.2 m) apart in the other for a total grid area of 12 x 8 feet.. Even in ideal conditions on the perfect site, a shed floor will be exposed to some moisture, and in time, untreated lumber will rot. for the shed's floor deck, use