The Avila Adobe was built in 1818 by Francisco Avila and has the distinction of being the oldest standing residence in Los Angeles, California. It is located in the paseo of historical Olvera Street, a part of Los Angeles Plaza Historic District, a California State Historic Park. The building itself is registered as California Historical Landmark #145, while the entire historic district is both listed on the National Register of Historic Places and as a Los Angeles Historic-Cultural Monument.
The Plaza is the third location of the original Spanish settlement El Pueblo de Nuestra Señora la Reina de Los Ángeles sobre el Río Porciúncula, the first two having been washed out by flooding from the swollen Río Porciúncula (Los Angeles River). The Avila Adobe was one of the settlement's first houses to share street frontage in the Pueblo de Los Angeles of Spanish colonial Alta California.
The walls of the Avila Adobe are 2.5–3 feet (0.76–0.91 m) thick and are built from sun-baked adobe bricks. The original ceilings were 15 feet (4.6 m) high and supported by beams of cottonwood, which was available along the banks of the Los Angeles River. Though the roof appears slanted today, the original roof was flat. Tar (Spanish: brea) was brought up from the La Brea Tar Pits, located near the north boundary line of Avila's Rancho Las Cienegas. The tar was mixed with rocks and horsehair, a common binder in exterior building material, and applied to beams of the roof as a sealant from inclement weather.
The original floor of the Avila adobe was hard-as-concrete compacted earth. which was swept several times a day to keep the surface smooth and free from loose soil. (Dirt floors were common among most early adobes.) In later years, varnished wood planks were used as flooring.
The original structure was nearly twice as long as it now appears and was "L"-shaped with a wing that extended nearly to the center of Olvera Street. The rear of the house had a long porch facing the patio. Francisco tended a garden and a vineyard in the rear courtyard. The nearby Zanja Madre (literally "Mother Ditch") was a main water aqueduct and irrigation ditch that brought water down to the Pueblo from the Los Angeles River and was close enough to the adobe for Francisco Avila to avail himself. Avila eventually added a wooden veranda and steps to the front of the adobe.(Wikipedia)