A Garden Wall Leaning Over: How Serious Is It and What Fixes It?

Foundations are the usual culprit. Many older boundary walls were built on a shallow footing or on no proper foundation at all, and on the clay soils common across much of Essex that ground shrinks in dry summers and swells again in wet winters. The wall rides that movement until it no longer comes back.

Tree roots are the second cause, working under and against the footing, and they also amplify the clay effect by drawing moisture out of the ground in summer.

Retained soil is the third and the most serious. A wall that has a raised bed, a bank or a driveway behind it is holding back ground pressure it was probably never designed for, especially when that ground is saturated. Walls holding back soil need to be built as retaining structures with proper thickness, reinforcement and drainage behind them.

Finally there is simple age: soft lime mortar eroded out of the joints, frost damaged bricks and missing coping that has let water into the top of the wall for years.

Look for a bulge in the face rather than a uniform tilt. A wall that has bowed outward in the middle has usually lost its bond internally and is much closer to failure than one leaning evenly.

Check the mortar joints. Wide open horizontal cracks, stepped diagonal cracking, and joints you can push a finger into indicate active movement. Fresh crack faces look clean and light compared with the weathered brick around them, which suggests recent movement.

You can monitor a suspect wall cheaply. Fix a piece of glass or a card across a crack, or mark and date pencil lines across it, and check over a few weeks. If it opens further, the wall is moving now.

Treat as urgent any wall over about a metre that is bulging, any wall that has moved noticeably in recent weeks, and any leaning wall next to a pavement, a parking space, a play area or a route children use. Fence it off and keep people away from it rather than waiting.

Repointing is worthwhile on a wall that is essentially sound and upright but has eroded joints, and adding or repairing coping to keep water out of the top is one of the best value things you can do for an old wall.

A leaning wall cannot be repointed straight. Once a wall is out of plumb the practical options are taking it down and rebuilding it, often reusing the bricks, on a proper foundation, or rebuilding to a lower height where full height is not essential.

Where soil is being retained, the rebuild needs to be designed for that: adequate thickness or reinforcement, and drainage behind the wall so water pressure is not building up against it. Skipping the drainage is the reason a lot of rebuilt retaining walls fail a second time.

Sometimes the honest recommendation is not a wall at all. Where a boundary wall has failed repeatedly and is not retaining anything, a fence on concrete posts is a fraction of the cost and does the same job. We will tell you when that is the sensible answer, and our structures and fencing work is covered by our ten year guarantee.