On Thu, 13 Mar 2008 04:09:06 -0700 (PDT),
wrote:

Thanks for your replies!!

My wall is about 3' high & 25' long- hasn't moved a hair in 5 NY
winters. * It is serpentine & I think that adds to both appeal and
strength.

Jim, that's good to know! I like the idea of serpentine walls too. I'm
concerned, though, that building one wall above another will create
additional issues over and above the construction of one wall--what do
you think?

In my part of the world- and in my yard- it wouldn't be a problem. I'd
be more concerned if I lived across the street on a big clay hill- or
in some place that gets a lot more rain than we do.

But that's where your local landscape guy, the building inspector, or
the nursery & county extension folks that Norminn mentioned might be
able to help.

Jim