Bastides began to appear in numbers under the terms of the Treaty of Paris (1229), which permitted Raymond VII of Toulouse to build new towns in his shattered domains, though not to fortify them. When the Capetian Alphonse of Poitiers inherited, under a marriage stipulated by the treaty, this "bastide founder of unparalleled energy" consolidated his regional control in part through the founding of bastides. The bastides were also an attempt by landowners to generate revenues from taxes on trade rather than tithes (taxes on production). Farmers who elected to move their families to bastides were no longer vassals of the local lord — they became free men; thus the creation of bastides was a force in the waning of feudalism. The new inhabitants were encouraged to work the land around the bastide, which in turn attracted trade in the form of merchants and markets. The lord taxed dwellings in the bastides and all trade in the market. The legal footing on which the bastides were set was that of paréage with the local ruling power, based on a formal written contractual agreement between the landholder and a count of Toulouse a king of France or a king of England. The landholder might be a cartel of local lords and the abbot of a local monastery.

Responsibilities and benefits were carefully framed in a charter that delineated the franchises ("liberties") and coutumes ("customs") of the bastide. Feudal rights were invested in the sovereign, with the local lord retaining some duties as enforcer of local justice and intermediary between the new inhabitants— required to build houses within a specified time, often a year— and the representatives of the sovereign. Residents were granted a houselot, a kitchen garden lot (casale) and a cultivable lot (arpent) on the periphery of the bastide's lands. First constructions of the hall and the church were often of carpentry: stone constructions came after the successful founding of the bastide.