Your basic options are to design and build one from scratch; order a set of plans online and gather the materials yourself; or buy a kit with all the materials cut to size that you assemble. Whatever route you take, elevate it off the ground on footings, blocks, or patio stones to protect the base from rot.
In most Canadian jurisdictions, as long as the footprint of the structure is under 10 square metres, you won’t need a building permit, but you should check with the local building department to make sure. You’ll also want to make sure that you’re not too close to property lines or your shoreline.
Wood is the classic choice, but you’ll need to paint or stain it to protect the lumber. Some ready-made kits are constructed with durable metal or PVC walls. If you plan on storing larger items inside, you might want to use barn-style doors and a window or two will bring in natural light. Up top, you could finish the roof with shingles or cedar shakes, but a steel roof will last forever and is available in a variety of colours and finishes.
To maximize your storage space, build in some shelves and mount some hooks so you can hang things on the walls or from the ceiling. If your roof design has rafters, you can also store items up there.
Need an extra room in the cottage? Consider building a double-duty structure that you can use as a storage area and bunkie. A bunk bed in the bunkie makes for a fun kids’ getaway. Or forget the kids, and build it for yourself!