Page 110 - Masonry and Concrete

Understanding Masonry
109
UNDERSTANDING MASONRY

plants. Although soft when first quar-
ried, limestone becomes harder with age
and exposure to the weather. Because it’s
much more porous than granite, lime-
stone is not as durable in cold and wet
climates where it is exposed to repeated
cycles of freezing and thawing. Lime-
stone is generally cream or buff colored,
but it may also be reddish or yellowish or
have a grey tint.
Limestone is available as fieldstone
and quarried rubble, as saw-cut ashlar,
and sometimes as flagstone. Because it is
softer and more porous than granite, lime-
stone is also easier to work with and to
shape with hand tools and small saws.
Since its softness also makes it less expen-
sive than granite, limestone is frequently
used for both residential and commercial
work.
Sandstone varies in color from buff,
FIGURE 4-19
pink, and crimson to greenish brown,
cream, and blue-gray. Light-colored sand- Rubble stone and ashlar used together.
stone is usually strong and durable. Red-
dish or brown sandstone is typically softer
and more easily cut. Sandstone is available as fieldstone and quarried
rubble, as ashlar, and as flagstone split into thin slabs for paving. Sand-
stone is easier to cut and work than granite, but more difficult than
limestone.
1
Slate is usually split into slabs 4 in. or more in thickness. It’s
used for flagstone, flooring tiles, and roofing. Small quantities of var-
ious mineral ingredients give color to different slates, ranging from
black, blue, and gray, to red, purple, and green. “Select” slate is uni-
form in color and more costly than “ribbon” slate, which contains
stripes of two or more colors. Slate is very durable as a paving mate-
rial because it has low porosity and high resistance to the abrasion of
repeated foot traffic. It is moderately easy to cut and shape, but is
very brittle.

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