I can't speak to whether or not it's a good idea, but I can tell you that the previous owner of my house did this in the front yard. They actually put a railroad tie retaining wall in front of an old concrete one and filled in between with gravel. I just took the railroad tie one down (and was surprised to find there was another wall in there!) but the railroad tie wall had been there for at least 15-20 years. The concrete one was probably closer to 30 years old--the age of the house. As long as you fill with gravel for excellent drainage and build a good foundation, it seems like your wall should last.

My hesitation would be the chemicals in the wood. Railroad ties are treated with nasty chemicals that you might not want leeching into your ground. If you're not growing food, it probably doesn't matter.

I think your basic plan is reasonably sound. But the fact that there's already a wall there does not give one license to build another wall that is less strong, thinking that the existing wall will share some of the burden. Over time, the new wall will take on all of the forces of a glacier-like earth. Having observed so many walls fail over time, I'm personally a firm believer in overbuilding when it comes to retaining walls. Even accepted residential specs don't seem strong enough in my opinion. (They're usually strong enough to pass the problems on to one of the subsequent property owners!) Also, the layout of the wall can make a difference in it's strength. A long run of straight wall is the weakest design. Whatever new wall you make, I would follow the rules for one of the conventional types of drainage. I would not fill gravel solid between both walls. It's not necessary to do that and it could be troublesome elsewhere (like planting.) But the good foundation, as puffie says, is essential.

How high of a wall are we talking about? And when you say stone, do you mean drystacked natural stone or something else?

Thanks for the comments. The new wall will be a thick dry stacked wall that ranges in height, but will be strong enough to hold things up on its own. The upper area is a tennis court, with lawn below, so chemicals are not a big issue. I figure if there is some subsistence over time, we can fill in the edges. I like the idea of breaking up the straight lines to avoid a long run!

Most walls do vary in height. Put another way: how tall will the wall be at its highest point?

I see that these postings are from 2012, but I have a similar question to that of GilBagnell. An old railroad tie wall borders our driveway about one foot out from it, runs 75 feet long and tapers down from 4 feet at the highest point. We would like to either replace it with boulders or place boulders in front of the existing ties if there's enough room. What are my options?

artlink, start a new thread with your project. And be sure to include a photograph that explains as much as possible.