The front of the mission (what you see from the parking lot) looks quite similar to what you would have seen in 19th century.
Mission Drawings / Layouts / Measurements / Building Materials
When I read your question I thought of the written reports the padres had to submit each year to the authorities in New Spain. The reports listed numbers of livestock, crop production, the number of sacraments administered, etc. And they all contain numbers written by the Franciscans that will satisfy the question. These reports are available at:
Santa Barbara Mission Archive Library.
2201 Laguna Street
Santa Barbara, CA 93105
Telephone: (805) 682-4713
The actual construction of the mission buildings usually began with the construction of temporary structures, with the work done by the founding missionaries and the soldiers and neophytes who were part of the founding party. The mission buildings (the church, padres quarters, quadrangle, neophyte housing, storehouses etc.) evolved over decades and in most missions, construction and repair was continuous. The building was done under the overall supervision of one of the padres but the actual work was performed by the Indian neophytes.
The missions had most of the same tools that you would have found in any civilized country in late 18th century. They brought tools with them and early in the history of each mission high priority was given to creating workshops (carpentry shops, a blacksmith shop etc.).
The initial buildings were made of wood and local materials. Ultimately they built buildings of adobe brick, using the local soil and hay.
Mission San Jose was the 14th mission build in California - 28 years after the mission beginnings in San Diego, so there was more of an infrastructure in place to support its establishment. It was one of four missions established in 1897 under the leadership of Fr. Fermin Lasuen, the second Father President.
The area was identified by a scouting party in 1795. Goods and implements for the new missions were sent from Mexico. Fr. Lausen personally led the founding party which set out from Mission Santa Clara on June 9, 1797. On June 11 they raised a cross at the spot.
San Luis Rey de Francia was secularized in 1834, and the buildings were stripped and abandoned in subsequent years. In 1846 some of the buildings were occupied by the U.S. Army during the Mexican American War. The famous Indian scout, Kit Carson was with the army detachment encamped at the mission. Even though San Luis Rey was returned to the Church in 1865 the mission was essentially abandoned between 1865-1892. During this time the quadrangle collapsed and portions of the church caved in.
When any mission was first "founded" the organizing party of padres, soldiers and neophytes from nearby missions had to erect temporary crude structures out of wood and other local materials. Gradually over the next few years more elaborate buildings were constructed, typically with adobe bricks.
Construction on the present San Jose church started in 1805, about eight years after the mission was founded. The church was destroyed by an earthquake in 1868, partially restored in 1916 and 1950 and extensively reconstructed in 1982-85.
This varies by mission.
There was a drawing of the San Jose Mission layout done in 1854 but it is hard to read. An oversimplified colored version we have used in lectures appears below:
San Buenaventura is a beautiful mission. I assume you are building a model.