A permit is required for any construction or alteration the requires the Building Department to do an inspection using the technical codes (see Ordinance 2005-29).
The Florida Building Code Section 102.2.5 allows the Building Department to exempt owners of a single-family residence from certain permitting requirements.
Structures exempted by this rule:
Detached and attached buildings or structures that are not used for habitable space and are 400 square feet or less in floor area
Additions to living space that are 100 square feet or less in floor area
In both cases, the structure must be built by the owner and must lie outside the Walton County Coastal Building Zone.
Accessory Uses which are not heated or cooled do not require a building permit when constructed by the property owner outside the Coastal Building Zone. They must be free-standing, detached, and less than 400 square feet.