Retaining wall condition assessment
An inspection of an existing garden, boundary or basement retaining wall to assess its condition and whether it remains stable.
About this service
An existing retaining wall rarely gives no warning before it gets into trouble. Bulging brickwork, a lean towards the low side, open joints, cracks that widen towards the top, wet patches and missing weep holes are all clues. A condition assessment reads those clues and tells you whether the wall is stable as it stands, whether it is slowly getting worse, and what it would take to make it safe for the long term.
London has a great many old retaining walls that were never designed in the modern sense. Victorian garden terraces, railway-side boundaries, front area walls to basement flats and walls holding back raised gardens in hilly parts of Greenwich, Bromley and Harrow were often built in brick or stone with no drainage and no reinforcement. Many have stood for over a century, but tree roots, extra loading and blocked drainage can tip the balance.
We inspect the wall, the ground above and below, nearby trees and drains, and anything adding load behind it. Our report gives a clear opinion on stability and a practical recommendation, whether that is monitoring, local repairs, partial rebuilding or a full replacement. Every inspection report we issue is signed off by a chartered engineer who is a Member of the Institution of Civil Engineers (MICE). Fees start from £500 + VAT.
When you need it
- A retaining wall is leaning, cracked or bulging
- You plan to build or dig near an existing retaining wall
- A neighbour's wall is causing concern
What's included
- Inspection of the wall and its surroundings
- Assessment of drainage, loading and visible defects
- Opinion on stability
- Repair or rebuild recommendations
How it works
- Background and accessWe ask about the wall's history, who owns it, when you noticed changes and what sits behind it. We confirm the fixed fee in writing and arrange access to both sides of the wall if possible.
- Inspect the wallWe measure lean and bulging, record cracks and joint condition, check for drainage outlets and look at the top of the wall for heave, loading, trees and ground cracking.
- Assess the causesWe consider soil type, water, surcharge and root action together, because the visible defect is usually the result of several factors acting over many years rather than one single event.
- Report and recommendationsYou receive a written report with photographs, our opinion on stability and ranked options, from simple drainage improvements and repointing to propping, partial rebuild or full replacement.
What you receive
Shared and neighbouring retaining walls: who is responsible?
Ownership is often the first question when a boundary retaining wall moves. As a general rule the person whose land is higher is responsible for holding it up, but title deeds, past agreements and the wall's position can change that. Our report records the condition and likely causes objectively, which gives both owners a shared starting point. Where work will affect a neighbour's land or wall, the Party Wall etc. Act 1996 may also apply, and our party wall guide covers the basics.
If you plan to excavate near an old wall, for example to lower a garden for a driveway or add a lightwell, an assessment before work starts is wise. Digging at the foot of a retaining wall removes the ground that resists sliding, and old walls can fail suddenly. Where replacement is the answer, we can move straight on to retaining wall design. If the wall looks dangerous now, a dangerous structure inspection is the faster route.
Not included
- Ground investigation and detailed redesign, available separately
Frequently asked questions
How do I know if a retaining wall is failing?
Look for a lean that is getting worse, bulges in the face, diagonal or horizontal cracks, bricks pushing out, gaps opening at the top between the wall and the ground, and wet staining with no weep holes. Any one of these deserves an inspection. Rapid change, or movement after heavy rain, should be treated as urgent and the area below kept clear.
Who is responsible for a retaining wall between two gardens?
Often the owner of the higher ground, because their soil is being held back, but it is not automatic. Title deeds, boundary agreements and who built the wall all matter. A structural report does not settle legal ownership, but it gives both neighbours an independent view of condition and causes, which helps any discussion or legal advice that follows.
Can a bulging retaining wall be repaired rather than rebuilt?
Sometimes. Where movement is old and slow, improving drainage, removing extra load, repointing and adding local restraint can extend the wall's life. Where the bulge is large, active or the wall is thin for its height, rebuilding is usually safer and cheaper in the long run. The assessment tells you which side of that line your wall sits.
Do tree roots damage retaining walls?
Yes. Roots can grow into joints and push masonry apart, and trees growing just behind a wall add load and dry out clay unevenly. Removing a large tree can also cause clay to swell over time. We note nearby trees in the report and explain whether they are contributing and what, if anything, should be done about them.