What you are asking is how do I build a shed. Sitting here for an hour is beyond most peoples available "free" time. Go to any timber merchants and garden centres and see how the sheds are constructed. There are hundreds of ways of doing what you want to do so jusy check out your own methods with what has already been done. As it says obove every topic on this forum, check the projects first, all the timber sizes you need are in there under joists.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!