Great shed, yes it is pre-fab, it looks like it will stand up to the elements. The assembly took me and my 12 years old son five hours from start to finish, including unpacking and complete breakdown of the waste. 

Follow the instructions closely or you will be going backwards to redo a section or two. We actually wasted 30 minute because we got ahead of ourselves. Your platform has to be at a MINIMUM of 100 inches wide by 72 inches deep. 
The shed fit right up to the edge of our platform that measure exactly to the aforementioned inches.  See the pictures to reinforce my last statement.   

This was well worth the price and the investment.