Then, you will need to install a series of floor joists across the entire length of the support beams; these will need to be the same length as the distance between the two rim joints so that they’ll fit between them. In the example design, the floor joists are all separated by 14.5-inch gaps except for the outermost two, which are 13 3⁄4 inches (34.9 cm) from their immediate neighbors; this is to allow a standard piece of plywood to line up with the outermost edge of the outermost joist but only cover half of an interior joist, allowing its neighbor to cover the other half so that both can be supported properly.[3]
Water is wood's worst enemy. Given the right circumstance and enough time, excessive moisture can rot framing, warp floors and doors, corrode hinges and breed mold and mildew. Fortunately, there's an easy remedy. First, be sure that the lowest wood member--the mudsill--is at least 6 in. above the ground. That's sufficient space to allow fresh air to circulate under the shed.

Working from ladders is more dangerous than working from scaffolding. Plus, having to constantly move ladders around is time consuming. When you get to the roof construction, consider renting a set of scaffolding with wheels. You’ll be amazed at how much easier it is to have a stable platform to work from and to set your tools and materials on. You can rent a 5-ft.-tall section of scaffold with three planks and wheels for about $110 per week.

DIY Shed Plans