 In the southwest United States and Mexico adobe buildings had massive walls and were rarely more than two stories high. Adobe mission churches were never more than about 35 feet (11 m). Since adobe surfaces are fragile, coatings are used to protect them. These coatings, periodically renewed, have included mud plaster, lime plaster, whitewash or stucco. Adobe walls were historically made by laying the bricks with mud mortar, which swells and shrinks at the same rate as the bricks when wetted or dried, heated or cooled. Modern adobe may be stabilized with cement and bonded with cement mortars, but cement mortars will cause unstabilized adobe bricks to deteriorate due to the different rates of thermal expansion and contraction.
