Although many Spanish missions had comparable elements, such as white plaster buildings, red clay roof tiles, tiny windows, and exposed beams, the founding priest picked the aesthetic and decorative accents. Many traditional architectural characteristics have been kept in Spanish mission architecture over the years. The most important element to understanding the culture of the time is that these churches were designed by Catholic priests who followed the rules set out by their church in Rome. They were built according to a strict plan with precise measurements, using only native materials. The buildings were usually one story high with an open interior space divided into a number of smaller rooms. Small windows let in some light but provided protection from the elements. Walls were made of adobe or masonry. The roofs were made of wood or metal. There were no electricity supplies at Spanish missions until 1882 when the first electric lights were installed at San Diego de Alcalá. Each mission was unique although they had several common features. They all began with a square ground floor area enclosed by a wall. The church was located in the center and the living quarters were on either side. A patio (a covered porch) separated the two sections of the house. A narrow alley called the calle (lane) led from the street to the front door of the house.