Hi Walter,

I have a 2' tall retaining wall in my garden.
It consists of 6x8 railroad ties, set on edge.

Are we talking three rows 8" high, or four rows 6" high?

The wall would be stronger if the ties were laid flat, but that does mean
an extra row of ties.

The rr-ties are laterally supported by treated 4x4 lumber posts,
imbedded about 1' into concrete supports poured into the soil
on the low side of the wall. there is no concrete
footing for the RRties, they are set on the soil.
All this is now 30 years old. The RR ties are still in good shape but
the treated 4x4 have rotted/broken-off at the base of the wall.
Therefore, the RR ties are slowly being pushed downhill, collapsing
the wall.

Have you dug down on the back side of the wall to see what the back sides
of the ties look like? After 30 years I would question whether they're as
good as they might appear, especially if the treated 4x4's have rotted.

I had some old ties along our driveway that looked fine from the front, but
underneath they were completely rotted away. If your ties are rotted,
you're better off building a new wall.

If I could replace the 4x4 posts in their cast concrete bases, I could
easily re-align the RR ties. How can I replace the 4x4 posts, set in
concrete? Do I need to dig out the concrete base and re-pour new
concrete around a new post? That's hard work for an 85 year old.

Unfortunately, there's no easy way to repair your wall. You'll need to dig
the dirt back from behind the wall to position the wall back where it used
to be. You probably won't be able to just push things back into alignment.
It would probably be easier to take it apart and reassemble in the new
position.

Granted, this won't be easy at 85, or even at my age of 51. Maybe you can
find some young bucks with more brawn than brains?

Two feet is not an overly high retaining wall, but it's usually the water
in the soil that pushes it forward. You can help reduce the problem by
installing drainage pipe, gravel, and landscape fabric behind the wall.
Then route the drain away from the wall.

If you have room, you might be able to save some work by rebuilding the
wall in front of it's original position. That would give you room to
install drainage behind the wall without digging a lot of dirt.

If it comes down to rebuilding the wall, you may want to look at other
options. Precast blocks are popular and widely available, but they can get
expensive for long walls. Or, you can dry stack rocks with a slight
backward slope. You could build forms and pour a concrete retaining wall.
Or, you could do what I did and build a mortared stone retaining wall:

http://www.watsondiy.com/2008wall.htm
http://www.watsondiy.com/2009wall.htm

If you decide to stay with railroad ties, you could probably forego the 4x4
posts. Just overlap the rows of ties, stepping each row back slightly. Then
drill holes down through the ties and anchor them together with sections of
rebar. If the wall is very long, or the soil slopes uphill behind the wall,
you might want to install a "deadman" behind the wall every 8' or so. The
first row of ties should also be buried below ground level to prevent the
bottom from being pushed out (alternatively, you might be able to drill
holes into the old concrete from the 4x4's and anchor to those).

Good luck with your project!

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com