Why retaining walls lean — and how to fix one properly.

A retaining wall has one job: hold back soil that wants to move. Soil is heavy. Wet soil is heavier, and saturated soil behind a wall with no drainage pushes harder with every storm. That’s why most of the leaning walls we’re called to share the same story — they were built as a face, not as a structure.

The usual causes.

• No drainage. Without drainage stone behind the wall and a way out for the water, rain saturates the backfill and the pressure builds.
• No footing. A wall set on topsoil or loose fill settles unevenly and begins to tip.
• Clay backfill. Clay holds water and swells — the worst material to pack directly behind a wall.
• Too tall for how it was built. A wall that holds at two feet can fail at five built the same way.
• Roots and downspouts. A tree growing at the wall line, or a gutter emptying behind it, will find the weak point.

The warning signs.

• A face that leans or bulges.
• Cracks that step diagonally through the joints.
• Soil or water seeping through the face after rain.
• A cap stone separating from the wall.
• Ground behind the wall sinking or cracking.

How a wall should be built.

Every wall we build starts the same way: read the ground, then build the structure before the face.

1. A footing on solid ground, below the frost line. Fairfax County requires footings to bear on solid ground at least 24 inches below grade; Montgomery County’s frost line is 30 inches. Other jurisdictions set their own depth.
2. Drainage behind the wall — drainage stone and a drain line that carries water out, not down into the footing.
3. Backfill that drains, not clay packed against the stone.
4. Stone set in courses and tied together, so the wall works as one piece.
5. A cap that sheds water off the top and finishes the line.

Patch or rebuild?

Repointing the face of a wall that’s being pushed by water is paint on a crack. If the wall is leaning, the lasting fix is to take the failing section down, build the footing and the drainage it never had, and rebuild it — reusing the original stone wherever it’s sound, so the repair disappears into the wall.