The earliest structures had roofs of thatch or earth supported by flat poles. "Tejas" (roof tiles) were utilized in later construction (beginning around 1790) to replace the flammable thatch. The semicircular tiles consisted of clay molded over a section of a log was which well-sanded to prevent the clay from sticking. According to the accounts of Father Estévan Tapís of Mission Santa Barbara, some thirty-two Native American males were required to make 500 tiles each day, while the women carried sand and straw to the pits. The mixture was first worked in pits under the hoofs of animals, then placed on a flat board and fashioned to the correct thickness. Sheets of clay were then placed over the logs and cut the desired to size: they ranged in length from , and tapered from in width. After trimming, the tiles were dried in the sun, then placed in ovens and burned until they took on a reddish-brown coloring. The quality of the tiles varied greatly among the missions due to differences in soil types from one site to another. Legend has it that the first tiles were made at Mission San Luis Obispo, but Father Maynard Geiger (the Franciscan historian and biographer of Junípero Serra) claims that Mission San Antonio de Padua was actually the first to use them. Aside from their obvious advantage over straw roofs in terms of fire retardance, the impermeable surface also protected the adobe walls below from the damaging effects of rain. The original tiles were secured with a dab of adobe and were held in place because of their shape, being tapered at the upper end so they could not slide off one another.