I am planning build two successive retaining walls 2' high (4' from
bottom of footer to top of the wall), and approximately 38' long.
The horizontal distance between the two walls will be approximately
three feet, with a step of 2' from the top of the bottom wall to the
top of the top wall, thus forming a small 3' planting terrace in
between. The total drop from top to bottom will be 4'.
I live in Southern California, so there is no frost line or threat of
freezing. The soil at 2' feet below grade is a composite of hard
clay/ virgin rotted sandstone. Both walls will be holding back a flat
grade. The newly formed terrace was previously a rounded/sloped mass
of unsupported earth, which was luckily only 4' high. The area above
the top wall runs flat to the back of the lot. Permitting is only
required for walls that are greater than 4' in height in my area.
My plan was to dig down to 2' below grade for each wall and pour a
concrete footer that is 8" in depth and 2' wide. I was planning on
using standard 8x8x16 cinder blocks for the wall itself. Based on
this, roughly two courses of cinder block would be below ground, while
another three would be above (yielding an exposed height of 2' for
I am going to use rebar to tie the retaining wall to the footer, as
well as to provide lateral support through bond beam block running the
length of the wall. I will also fill and cap all blocks with solid
concrete. Both walls will be water proofed, be back filled with gravel
(covered with filter fabric to prevent clogging) and have a sloped
perforated drainage pipe leading water away from the wall.
The reason I have decided to build in this manner, rather than using a
pre-cast concrete dry stacking system, is that I plan, for aesthetic
reasons, to face the above ground sections of both walls with flagstone
I have a few questions about this setup.
1. Do you think the placement of the top wall in proximity the bottom
wall would present any structural issues? If so, should I reduce the
size and depth of the footer in the top wall, thus reducing overall
2. Do I have to worry about moisture with regard to the underground
courses of cinderblock? If so, should I raise the footer?
3. Given that I am building a French drain, would I even need any weep
holes in the wall?
I am trying to build the most stable structure possible, but am worried
that I might be going into overkill mode. Any suggestions on my
questions above, or better way to build a similar type wall while still
allowing me to face with flagstone veneer would be very much