Visitors to San Diego are struck by how narrow it is and by how high and narrow the windows are.

The mission is so narrow because, the Franciscans had no practical way to string longitudinal supports together. The mission could only be as wide as the tallest trees which could be harvested.

The placement of the windows, and their width were also dictated by the crude building techniques employed. The lower the windows were, and the wider they were, the more weight their horizontal sills would have to bear.