Make a paper model of your hexagon shed. Draw six pentagons, five hexagons and five squares to create the model. Design it so that all of the sides are the same size so that they fit together flush.
Cut out the shapes, leaving an additional tab of paper on each shape.
Glue the shapes into the form of a shed by gluing down the tabs on each piece. One hexagon will create the very top of the shed, surrounded by five pentagons and then five more hexagons. Leave space for a door and fill in the remaining gaps with squares of paper.
Construct the shed using plywood sheets. Based on your model, draw six pentagons, five hexagons and five squares on the plywood. Saw out the pieces.
Create a frame using either PVC pipe or steel tubing. Connect the tubes by bolting them together, matching them to the sides of the plywood shapes. Using your model as a guide, bolt the plywood shapes to the PVC pipe or steel tubing.
Waterproof the structure with marine shrink-wrap or a waterproofing finish.