Page 107 - Masonry and Concrete

Understanding Masonry
106 CHAPTER FOUR

cut into small squares or rectangles and has
sawn or dressed faces, but the face may also
be left slightly rough. The free-form look of
a rubble stone wall is quite different from
the more formal pattern of an ashlar stone
wall (Figure 4-18). Rubble and ashlar cut
stone can be used together where their dis-
tinctly different appearance creates con-
trasting elements in a wall (Figure 4-19).
Flagstone may be a quarried material
that has been cut into flat slabs for use as
paving, a field stone that is naturally flat
enough for paving, or a stone that natu-
rally splits into thin layers. Flagstone
1
ranges from 2 in. to 2 in. thick and may
be shaped in either rough mosaic form or
geometric patterns (Figure 4-20).

4.5.2 Common Types of Natural
Stone
Although there are many different types of
FIGURE 4-15B
natural stone, only a few are suitable for
Cast rubble stone. building. A good building stone must have
strength, hardness, and durability, but also
be workable. The degree of hardness of a stone dictates its relative
workability as well as its ultimate form and cost, and determines its
durability and weathering characteristics. A soft stone is easily work-
able with hand tools and therefore less expensive than a hard stone,
which requires machine cutting. Soft stones are also more porous and
have less resistance to damage from weathering. The most common
stones that satisfy the requirements of building construction are gran-
ite, limestone, sandstone, and slate. While many others, such as
quartzite, bluestone, brownstone, and serpentine, are available in
some parts of the country, they are used less frequently.
Granite is an extremely hard, strong stone noted for its long term
durability and resistance to weathering. Its color may be red, pink,
brown, buff, green, gray, or black, depending on where it was quarried.
Because it is so hard, granite must be cut and dressed at the quarry or

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