We have been using our 15' x 8' (Side Entry) Outdoor storage shed for several years and are very pleased with it.  It is spaceous and the double doors make for easy access.  It is weather-tight --- have not noticed any moisture (leaks) and very little dust accumulation. 
    Follow the suggestions in the manual regarding pouring/constructing the shed platform.  I elected to construct a ridgid "floor" from treated lumber set on a prepared surface.  One of the uses for our shed is to safely store our treasured Christmas and other holiday decorations.