Fix for a Leaning Retaining Wall
Shown: Roger Cook works on a cobblestone retaining wall.
Our retaining wall was built in the late 1920s by one of the first doctors in town, so it has some historical value. Now parts of it are leaning. What can we do to save it?
—Jean Porter, Spring Green, Wis.
Roger Cook replies: It's possible that there is a way to push a wall back in place without damaging the mortar joints, but I'm not aware of it. And even if it could be done, it would probably be mighty costly. My guess is that the leaning portions of the wall will have to be disassembled and rebuilt by an experienced mason, after the soil has been excavated behind it.
Now, if you really want keep the wall in its historical condition, each stone should be numbered and photographed before the work starts so that it can be put back in the same position. Be sure to get close-up shots as well as overall shots. You should also have the old mortar analyzed so that the new stuff will match the old in color and consistency.
But if history is less important than your budget, the stones can simply be removed, cleaned, and reassembled in a pattern that closely matches the existing wall.
Either way, the wall should sit on a thick footing of firmly tamped crushed stone with proper drainage at its base—a perforated PVC pipe wrapped in filter fabric and buried in round drainage stone should do the trick. Once rebuilt on its new footing, your wall should last at least another 80 years.