Figure 4-27.Coursed rubble masonry
approximately continuous horizontal bed joints, as
shown in figure 4-27.
The stone used in stone masonry should be strong
and durable. Durability and strength depend upon the
chemical composition and physical structure of the
stone. Some of the more commonly found stones that
are suitable are limestone, sandstone, granite, and
slate. Unsquared stones obtained from nearby ledges
or quarries or even fieldstones may be used. The size
of the stone should be such that two people can easily
handle it. A variety of sizes are necessary to avoid
using large quantities of mortar.
The mortar used in stone masonry may be
composed of portland cement and sand in the
proportions of 1 part cement to 3 parts sand by volume.
Such mortar shrinks excessively and does not work
well with the trowel. A better mortar to use is portland
cement-lime mortar. Mortar made with ordinary
portland cement will stain most types of stone. If
staining must be prevented, nonstaining white
portland cement should be used in making the mortar.
Lime does not usually stain the stone.