What is Masonry Analysis Masonry analysis is the study of the materials and techniques used in ancient construction. In Rome and Ostia, walls were faced and edged with combinations of tufa blocks and clay bricks. Masons likely worked in increments of one Roman foot at a time from the ground up, first laying the bricks with mortar and then filling in the wall with pozzolana core (a crude concrete-type substance of mortar and rubble that gave the walls great durability). Buildings were renovated numerous times as a result of the changing dynamics of the towns, imperial building programs, and the changing needs of the occupants. These different construction phases correspond to different patterns of brick and block facing on the walls. A careful examination of the walls, as well as the floors, doorways, and other features of each room, allows us to determine a relative chronology for the building phases. For more indepth information on the construction phases, click on the OSMAP Masonry Legend PDF. How is Masonry Analysis Performed? Masonry analysts investigate three aspects of wall construction: measurements, materials, and method. This information is gathered for the facing of the walls and any quoining or framing. A preliminary component of the masonry analyst's job is to determine if a wall (or part the wall) is original (i.e.entirely ancient), repointed (blocks and bricks are original, but mortar has been reapplied), or reconstructed. For original and repointed walls, the size of the bricks and blocks, the thickness of the mortar, the width, length and height of walls, the courses per meter (the number of bricks and blocks occurring over a span of one meter), as well as the mean, median, and mode of brick size are measured. Once measurements are taken, the qualities of the materials are examined closely. The color of the tufa blocks, bricks, and mortar, as well as the size and color of any inclusions (the bits and pieces of natural rocks, minerals or clay occurring in the tufa, brick, or mortar) are evaluated according to the Munsell chart. Any peculiar features of the wall such as abnormal materials used in place of bricks, or a significant amount of lyme leaching (the bleaching of the bricks or blocks that results from the emergence of lyme to the surface) are also noted. Two walls that yield similar enough information based on masonry analysis can be linked confidently to the same building phase, no matter how far apart they are located. Fig 1: View of a cut piece of marble egg-and-dart molding used in place of a brick. Notice also the substantial quantity and size of inclusions in the mortar. Fig 2: View of the North Wall of Rm. 18 illustrating significant lyme leaching on the bottom and eastern section of the latericium facing. Why is Masonry Analysis Important? One of the primary goals of this type of study involves dating. Masonry analysis can tell us when parts of a building were constructed or adapted in relation to its other parts. By separating out the earliest, intermediate and final building phases, we are able to understand more about how and why the composition of a building (or a complex of buildings) changed over time. Because the functions of buildings could change drastically (e.g. from private to public, or secular to religious) it is important to interpret each phase of building construction within its proper social-historical context. Perhaps there is no better test case for this assertion than the synagogue at Ostia. Scholars are still in disagreement over whether it was built originally as a synagogue or adapted from an already existing structure at a later date. Only further examination of the synagogue's complicated building phases, through masonry analysis and archaeological excavation, can help us answer this question.