I'm a little late with my response, but to answer your question, it depends on local building codes where you live, as well as your ability to look at the "Big Picture" and not miss some important details. I worked in various capacities and trades in the residential and commercial building world for 20+ years and felt competent enough to double the size of our recently acquired home. The most important thing is to build it safe and structurally sound. The only things needed to build in our small town were a permit for septic, a rough electrical inspection before the power company would connect a new service, and a rough frame inspection. Otherwise, because our town population was under 2000 people, we didn't have to meet state code. The state code would have required architectural drawing, a site survey, separate plumbing framing and electrical permits. Each would need both rough and finish inspections. I might add that when we has questions, I called the towns Code Enforcement officer. He was happy to see that I was willing to seek his advice, and follow it too! He even addressed a couple of items that I hadn't thought about, and weren't required, but made my project that much better. It's been 20 years since we finished it, and it's still standing straight and true, and we're still loving it all. Good luck with your project, it is worth it to be a part of it!