Page 171 - Masonry and Concrete

Masonry Construction Techniques
170 CHAPTER FIVE

both types of stonework, though, it will often be necessary to cut and
shape individual stones to make them fit better.
Granite is the most difficult stone to cut, but limestone, sandstone,
and slate are relatively easy to work with. To cut rubble, it is first laid
on solid ground for firm, even support. Cutting should not be done on
concrete surfaces because the hard concrete and uneven support may
cause the stone to break in the wrong place. The cut is marked with
chalk, crayon, or pencil, and scored with a chisel. Often, the stone will
break along the line before it is scored all the way around. Small lumps
or protrusions are removed with the pointing chisel. Flagstones can be
cut by laying them over a small pipe and striking with the chisel. Small
pieces can also be trimmed off of flagstone with a mason’s hammer.

5.5.2 Mortar for Stone Masonry

The same types of mortar used for brick and block construction are suit-
able for stone masonry work as well. Sometimes the proportion of lime
is reduced, and one popular mix uses 1 part lime, 2 parts portland
cement, and 9 parts sand or 1 part masonry cement to 3 parts sand.
Because stone is so heavy, the mortar should be mixed to a slightly stiffer
consistency than that used with unit masonry, even though a stiffer mix
is a little more difficult to work with. For light-colored stone, a light-col-
ored mortar can be made using white portland cement instead of ordi-
nary gray cement, or pigments can be added to create other colors.

5.5.3 Setting Stone

Ashlar stone that is laid in straight horizontal courses can be installed
using string lines and line blocks just like unit masonry. For rubble stone
that is less precise, pattern bonds are more like putting together a puzzle
in which no two pieces are the same size or shape. There is an art to cre-
ating uniformity in pattern so that the front of the house looks the same
as the sides and back. Colors must be blended and some regularity of
coursing and placement is required. The necessary skills can be acquired
only with hands-on experience and a good eye for the esthetics.

5.5.4 Flashing and Weep Holes
Even though stone is not as absorptive as brick or block, stone masonry
walls still require flashing and weeps to drain moisture from the wall.
Water entry in stone walls, like in brick and block walls, is most often

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