Squared-stone masonry is a rather ambiguous class of masonry. Compared to ashlar, the stones are not as precisely cut. However, some care is still taken in shaping stones, which differentiates it from the lower forms of the so-called rubble masonry. Squared-stone masonry is common, and, particularly where inherently well-shaped stones such as limestone and sandstone are available, this class of masonry is a good, relatively easy choice for structures.
The Traits of Squared-Stone Masonry
The stones in squared-stone masonry should be of good quality. The joints need to be less than one inch wide, but need not be tighter than one half of an inch. This results in more mortar use than in ashlar masonry; broadly, squared-stone masonry will use more than twice the amount of mortar as ashlar. The stones in squared-stone work are always longer than they are thick and also longer than they are wide. The stones themselves may even be left as they came from the quarry with little to no trimming. However, the stones may still be cut to give approximately straight edges, though without the precision required in ashlar.
In the final tally, squared-stone work results in a high-quality structure without the difficulty and expense required to make ashlar work.
Stone Arch Bridges 