Instructions / Assembly

19
L
andscaping with Timbers
Landscaping
The Safety of Treated Wood
Treated wood is safe in all
applications, from raised-
bed vegetable gardens to
garden benches. Once
the EXTRAGREEN™ is
fixed in the wood cells, it
is highly leach-resistant.
Pressure treated wood is
also durable and economical.
Because wood is a renewable resource, its use
makes good environmental sense.
Getting Down To It
Wooden Retaining Walls
A simple, low, wooden retaining wall on a
gentle slope with stable soil can be easily
built. Common wooden retaining walls are
constructed in two ways: timbers set into the
ground as posts to support planks, or stacked
timbers set directly on the ground.
Timber and Plank
For a timber and plank wall, digging the
holes for your posts is easily accomplished in
most soil with a two-handled clam shell
digger. Rocky soil may also require the use of
a digging bar to loosen the soil for the clam
shell digger. Power augers are great labor
saving tools if you have many post holes to
dig.
Set the posts 24 to 36 inches deep for a three-
foot high wall, deeper for a deep frost line (if
in doubt, consult your McFarland Cascade
®
dealer). The hole should be about 10-inches in
diameter for a 4”x6” timber. Place a base stone
or treated wood block in the bottom of the
hole as a post foundation.
Fill the timber holes with concrete. One and
one-half bags of ready-mix should be enough
for each timber (more for deeper post holes).
The fill should come 1 to 2 inches above
ground level and slope away from the post to
divert water. Allow the timbers to set for two
days before proceeding with retaining planks
and backfill (for plank material options, refer
to the McFarland Cascade
®
Treated Framing
Lumber chart on page 2. One-inch weep holes
drilled every four feet along the bottom plank
will improve drainage.
Stacked Timber
A stacked-timber retaining wall is a straight-
forward project. The bottom timber should be
set in a compacted trench below ground and
carefully leveled. Place a second timber on top
and bore a hole through both timbers with a
heavy duty drill and extension bit.
Drive a 3/4 inch pipe or rebar rod through
both timbers and well into the ground. Stag-
ger the joints as you add timbers and spike
them together on each side of every joint.
For drainage, occasionally leave a 1/4" to 1/2"
space at the joint
between timbers.
Retaining walls built
on very unstable soil
may require the
addition of a tie back
with a stationary
stabilization member
Wall
Timbers
Rebar
Fill
Original
Slope
Excavation
Line
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