Yes, porches require foundations. The type of foundation required, however, is determined by the type and use of the porch. For example, a screened-in porch won’t require a new cement foundation. However, if you turn your porch into a sunroom or plan on making it a living space, then chances are you need a foundation that’s more permanent than piers and posts. 

A Florida room is a home addition that has finished walls with windows lining the perimeter, while a screened-in porch, also known as an Arizona room, lacks windows and instead has screens to maintain constant ventilation. Florida rooms provide longer enjoyment throughout the year because they’re closed off and will naturally get heated from the sun, while a screened-in porch will just be the same temperature as the ambient air.

A screened-in porch can add value to your home, but it won’t count toward the total square footage at an appraisal or when it comes time to sell. A screened-in porch is not fully enclosed, usable year-round, insulated, or heated or cooled, so it doesn’t meet the requirements of livable square footage in most locations.

An Arizona room may or may not count toward your home’s square footage, depending on local regulations and the specifics of the room, but generally does not get included in the total square footage. In many locations, a room needs to be built to the same quality as the rest of the home, have an integrated heating/cooling system, and be habitable year-round to count toward square footage.