Page 364 - Masonry and Concrete

Retaining Walls
RETAINING WALLS
363

Lay the first course of units, butting
each one snugly against the next and fol-
lowing the string line for alignment and
elevation. Complete the entire first course
GRAVEL BACKFILL
before starting the second, leveling each
unit on its own (back to front and side to
side) and to adjacent units. Offset the sec-
ond course of units one-half the length of
the units in the course below to form a run-
ning bond. After the first two courses of
units are laid, begin adding the gravel and 2" SAND LEVELING BED
soil backfill behind the wall (Figure 10-19).
FIGURE 10-19
To give the wall a finished look, some sys-
Adding backfill.
tems include special solid cap units. With
other systems, cap units can be made from
regular units.

10.4 Dry-Stack Stone Gravity Retaining Walls

A dry-laid stone retaining wall may require considerable cutting and
shaping with the chisel to make a good interlocking fit. Easily work-
able stones like bluestone, sandstone, or limestone will usually be
the best. Dry-stack stone retaining walls do not require a concrete
footing. They may be laid directly onto the soil in an excavated
trench. In order to achieve stability, the wall must lean against the
embankment slightly, being tilted or battered toward the soil 2 in. for
every ft. of wall height (Figure 10-20). Dry-stack walls without a con-
crete footing are limited to a height of about 3 ft. At the base, a 3-ft.
wall should be 18 in. thick. The wall should sit in a 6-in. to 12-in.
deep trenched excavation. If necessary, 2 in. of sand can be placed in
the bottom of the trench to improve drainage. Dry-stack stone retain-
ing walls allow soil moisture to drain naturally through the open
joints so they do not require weep holes.
In soils or areas that drain well, excavate a trench along the length
of the wall 6 in. to 12-in. deep and 18–24 in. wide. Remove all grass,
sod, roots, and large rocks, and place a 2-in. bed of sand in the trench
for leveling the units. In dense or clayey soils, or in areas that do not
drain well, excavate 4–6 in. deeper and add a gravel or crushed stone

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