Size the trench so there's enough room for the retaining wall block and at least 8 in. of space behind it. Excavate deep enough to completely bury at least one full course, including space for 6 to 8 ...

Q: Tim, I’ve seen quite a few failed retaining walls. Many have bulges or have tipped over. What needs to be done to ensure I only do mine one time? I’ve seen photos of walls hundreds of years old ...