Despite the variety, there is common language that can be used to define one of these small structures. Cottages are one-story buildings that often have a hipped roof. In a cottage, overall square footage is limited, as is interior space. The ceiling may be open or might contain a sleeping loft and there could be a small garden or patio just outside the building. There are many definitions for a cottage, but here is a simple one from the travel industry dictionary: "A small, usually rural and rustic dwelling."
The roof of a cottage is usually peaked in the center, but does not have to be hipped. Gable and gambrel roofs are quite common as well. Roof material can also vary. In England or Holland, you might find a thatched roof, while a creole cottage along the Gulf Coast might have corrugated metal on a gabled frame. Asphalt shingles are still used, especially with new construction, but in places such as Denmark, red clay tiles are the most common material found on any roof, whether it is big or small.
With a reduction in building size and height, requirements for the foundation are also diminished. Although not out of the question, the presence of an underground basement decreases, too. Cottages are meant to be small, less-expensive buildings and the construction of a basement will usually work against that goal. Older cottages might be built on a stone foundation or brick piers, while a new "modern-style" cottage could be placed on a cement slab. It is even possible to have a split-level cottage.
Other common features with small cottage construction are open and exposed roof rafters. The smaller perimeter of these buildings make it easier to frame the roof without putting in an attic floor. The high peaked ceiling can also create a feeling of space, something that might be needed in a small bungalow or rustic hut. Of course, if a sleeping loft is desired, the addition of a floor that only covers part of the building is a popular choice that is found in many rural cottages.
Cottages, shacks and bungalows are convenient places to use natural materials. Roof materials and framing timbers have already been discussed, but using natural adobe or lime plaster on the exterior or interior walls is just one way to take advantage of natural materials. Wood shakes go well on either the exterior or interior wall, as does any kind of wood siding. Then there are the interior floors and outdoor walkways. Any one of these areas would look good with flagstone, brick or clay pavers. The best course of action is to search local markets for available materials and don't rule out the possibility of using salvaged materials.