We had a handyman put our shed together...the box of pieces was rather overwhelming.  We installed ours on existing concrete, since it does NOT come with a floor.  It's been up for almost 6 months (through an Oregon winter) and has kept all of our lawn and garden equipment dry and protected.  I'm only giving it 4 stars, though, because the siding material is rather weak and bends easily if bumped from the inside.