The time it takes to build a porch depends on the weather, availability of labor, and the homeowner’s schedule. Expect a porch-building project to take anywhere from three to 16 weeks to complete.  But keep in mind other factors that contribute to the length of the process, like the time it takes to get permits and the complexity of the porch design. A simple porch on a concrete slab will not take as long as a raised porch with a roof and columns.