In 1804 a row of buildings was constructed, measuring 232 feet in length and 19 feet in both height and width. This wing contained the temporary church (about 86 feet long), a sacristy (14 feet long), the padres' quarters (approximately 29 feet long), and the granary (103 feet long). With the aid of an initial group of Chumash neophytes from Missions Santa Barbara and La Purisima Concepción, this portion was constructed six months prior to the formal founding of Mission Santa Inés.
The 30-inch thick walls were made of adobe (regional soil that contained much clay). The roof consisted of poles over which sticks were laid side by side, and then covered with a layer of adobe soil that hardened, thus sealing out the weather. On September 17, 1804, Father Tápis officially dedicated the Mission to Saint Agnes.
The temporary brushwood shelter was constructed at which 200 Indians attended solemn High Mass. Twenty-seven children were baptized and 15 men enlisted for instruction in the Catholic religion. Fathers José Romualdo Gutierrez and José Antonio Calzada were selected as the first resident priests.
By the end of 1804 the Baptismal register already contained the names of 112 Chumash converts of all ages.