A building permit is required for a three-season porch, which is an enclosed structure, either heated or non-heated, requiring an insulated door between the two areas.
Insulation requirements depend on the heating option. Contact a building inspector for specific information. See the single-family lot guidelines for standard setbacks from your property line.
If a contractor is constructing the porch, the city requires the contractor to be licensed with either the state or the City of Maplewood.