Signs Your Retaining Wall Is Failing (And How to Fix It Fast)
- Andrew Waddington
- Jul 21
- 18 min read
Have you noticed cracks, a lean, or damp patches on your retaining wall? You’re not alone, and acting swiftly can save you time, money, and possibly avoid a full rebuild. A failing retaining wall can escalate from a cosmetic nuisance to a dangerous collapse with little warning.
The dramatic example above shows how an under-designed or poorly maintained wall can completely give way, threatening property above and injuring bystanders. In this guide, we’ll walk through common failure signs, why they happen, and practical stabilisation techniques that meet UK Building Regulations, all balanced against risk and cost considerations. By recognising the warning signs and taking action, you can safeguard your property and avoid disaster.
Why Retaining Walls Fail
Many garden and boundary retaining walls (especially older ones around homes in hilly areas like Yorkshire and Lancashire) were built without proper engineering. They might be too slim, lack adequate footings or drainage, or simply not be designed for the real pressure of the soil and water they hold back, leading to failure over time [1][2]. Below are the key reasons retaining walls commonly fail:
Lack of Structural Design
Walls installed “by eye” without calculations often lack the necessary thickness, steel reinforcement, or embedment depth to resist soil forces. Over time, an inadequately designed wall will almost always start to bulge or crack under pressure, sometimes abruptly. If an engineer underestimates the load or the builder cuts corners on materials, the wall may eventually give way.
Poor Drainage
Water is a retaining wall’s worst enemy. Without proper drainage, rain and groundwater accumulate behind the wall, dramatically increasing lateral pressure. In fact, lack of drainage is often cited as the most common cause of retaining wall failures [3]. Trapped water (hydrostatic pressure) can double the force on the wall, causing it to bulge, crack, or even collapse. Clogged weep holes or no drainage system at all means water has nowhere to go, like an overfilled balloon pushing against the wall until it bursts.
Inadequate Foundations
A retaining wall is only as stable as its base. If the wall has no proper footing or insufficient embedment into the ground, it can settle or tip forward. Foundations should be sized to spread the load and prevent the wall from sliding or overturning. Many DIY or poorly built walls have shallow, narrow footings that simply can’t handle the weight above or the pressure behind, leading to rotation or sinkage at the base.
Increased Loads (Surcharge)
Changes around the wall can add unexpected load. Parking a vehicle or building a shed right behind a wall, piling extra soil, or even heavy saturating rain can push a wall beyond its original limits. Soil itself is very heavy – roughly twice the weight of water – and when you add the weight of driveways, structures, or cars on top of the backfill, the lateral forces increase even further [4]. If a wall was not designed for these surcharges, it may start to lean or crack under the added pressure. Similarly, if soil properties change (e.g. becomes waterlogged), the effective pressure on the wall spikes.
Building Regs Oversight
In the UK, any wall retaining more than 1 metre of ground should involve proper design and approval, yet many DIY or “amateur” installations skip involving a structural engineer. This means they ignore critical safety standards. Local Authority Building Control (LABC) recommends that retaining walls over ~0.9 m high be engineer-designed (the NHBC even suggests over 0.6 m).
Unfortunately, we often see walls over a metre tall built without calculations or Building Regulations sign-off. These walls might hold up for a while, but they lack the verified stability that UK regulations demand for higher retaining walls (as outlined in Approved Document A for structure). The result is a ticking time bomb, a wall that isn’t officially compliant and may fail under stress.
Common Types of Retaining Walls
Retaining walls come in many forms, each with its own strengths and weaknesses. The table below gives a brief overview of common types, their advantages, limitations, and how they typically fail:
Type | Advantages | Limitations | Typical Failures | Graphic |
Traditional Gravity Wall (stone, masonry, block) | Simple construction; uses its weight to hold soil; durable for low heights. | Requires a wide base footprint; uses a lot of heavy materials. | Bulging/outward tipping if soil pressure exceeds the wall’s weight; base sliding if not enough mass. |  |
Cantilever Wall (reinforced concrete) | Slimmer profile with steel reinforcement; efficient for mid-height walls. | Higher construction cost; must be professionally designed. | Cracking or tilting at mid-height or base if under-designed or if reinforcement is insufficient. |  |
Segmental/Modular Block (often with geogrid) | Modular blocks are easy and fast to install; good drainage through joints; can be reinforced with geogrid ties. | Needs meticulous backfill compaction and geogrid layering for taller walls; limited height if unreinforced. | Wall movement or separations if poorly constructed – e.g. blocks start shifting or the wall bulges due to inadequate geogrid or poor backfill. |  |
Sheet Pile or Anchored Wall (steel, concrete or timber piles) | Suitable for deep excavations or tight spaces; can be installed where digging a wide base isn’t feasible; anchors/tie-backs can provide extra support. | Complex installation (requires driving piles or drilling for anchors); usually more expensive and needs specialist design. | Anchor failure or excessive deflection – wall can bow inwards if anchors corrode or lose tension; or piles can rotate if soil strength is overestimated. |  |
Gabion/Crib Wall (rock-filled wire baskets or interlocking crib frames) | Natural, rustic look; permeable (excellent drainage); environmentally friendly (can use recycled rock fill); flexible (can tolerate some movement). | Wire baskets can corrode over time; require regular maintenance; not suitable for very high walls without wide stepped design. | Bulging and fill loss – baskets may bow out or rupture as the wire rusts or if poorly filled; settlement can cause sections to slump. |  |
King Post (steel I‑beam + precast concrete or timber posts & sleeper infill) | Slim, modular system ideal for tight or sloping sites. Adjustable on-site. | Less visually appealing without cladding. Capacity is limited. Can be more expensive above ~3 m retained height | Post rotation or lateral movement if embedment or panel packing is insufficient. Infill slippage, cracking or decay (timber rot or concrete fracture). |  |
(The above are just a few examples. Other systems include criblock timber walls, propritary systems such as Tobermore Secura and novel Mechanically Stabilised Earth (MSE) solutions using geogrid-reinforced backfill such as Flex MSE etc. Each type must be chosen and designed according to the site conditions.)
How to Spot Key Warning Signs
If your retaining wall is starting to fail, it will usually give off visible warning signs. Don’t ignore these red flags – catching them early can be the difference between a simple repair and a total collapse. Here are specific signs of distress to watch for:
Cracks or Gaps in the Wall: Any cracking in the wall material is a cause for concern. Vertical or diagonal cracks that stair-step through bricks or blocks, or horizontal cracks along mortar lines, indicate the wall is moving. Hairline cracks may just be cosmetic, but larger cracks (several millimetres or more) are alarm bells. In particular, a horizontal crack near the base of a wall is serious – it often means the wall is starting to shear or overturn. If you notice wet cracks or water seeping through, it’s a sign of pressure build-up behind the wall due to poor drainage. Gaps forming between the wall and the soil it’s supposed to retain (i.e. the soil is pulling away) are another indication that the wall is no longer holding the ground in place.
Leaning, Bulging or Tilting: Stand to the side of your wall and see if it’s plumb (vertical). Any forward lean means the wall is losing its fight against soil pressure. A bulge in the middle of a masonry or block wall is a common failure mode as well – this indicates the wall is deforming outward. Even a slight lean or bulge (a few degrees or a few centimetres out of alignment) is a critical warning. Retaining walls should essentially be straight; if yours is curving outward or tipping, the forces may be overwhelming it. Often, water build-up or weak soil will push a wall outward until it eventually gives way. A rule of thumb: if you can notice a lean with the naked eye (or by holding a level against it), it’s time to take action.
Water Seepage or Damp Patches: If you see water trickling out of the wall, persistent damp stains, or even spurts of water through cracks after rain, it means water is trapped behind the wall. Weep holes (small drainage holes in the wall) should be draining freely. If they’re dry (during wet weather) or blocked, hydrostatic pressure is likely building up. Efflorescence (white salt deposits on the wall face) is another sign of water seeping through the masonry. Excess moisture not only adds pressure, but can erode the wall material and soil, exacerbating other issues.
Loose or Shifting Blocks/Stones: Inspect the face of the wall – are any blocks or stones protruding or have slipped out of alignment? In timber walls, are boards bowing or nails/bolts popping out? Movement of individual wall elements means the structure is destabilising. For brick or stone walls, check the mortar joints – crumbling or missing mortar and widening gaps between units suggest the wall is coming apart. In dry-stacked stone walls, any rocks falling out or bulging from the wall are a bad sign.
Sinkholes or Erosion at the Base: The ground in front of and behind the wall can also tell a story. If you notice sinkholes, depressions, or eroded gullies near the base of the wall, it could indicate soil is washing out from behind the wall (often through a crack or failed drainage outlet). A loss of backfill will remove support from the wall and hasten a collapse. Similarly, if the soil at the top of the wall is slumping or has pulled away from the back of the wall, the wall may be tilting outward. Any unusual changes in the terrain around the wall – like the retained slope above getting steeper due to soil movement – warrant a closer look.
Take these warning signs seriously!
Retaining wall failures can happen suddenly – what starts as a small crack in spring could turn into a bowed, leaning wall after one heavy winter of rain. If you spot any of the above issues, it’s wise to get a professional assessment sooner rather than later.
Practical Steps to Stabilise or Replace a Retaining Wall
If your retaining wall is showing signs of distress, there are several practical options to shore it up or, if needed, replace it. The right approach depends on the severity of the problem, the wall type, and your budget. Here are the steps to take, roughly in order:
Assess the Situation & Seek Expertise: Before any fix, you need to diagnose the cause of failure. Is it poor drainage causing pressure build-up? Is the wall too thin or lacking reinforcement? Has the foundation washed out? A qualified structural engineer – like our team at Shepherd Gilmour, should examine the wall. We will look at factors like soil type, drainage conditions, the wall’s construction, and any changes in loading (e.g. new driveway or landscaping) to determine the root cause. (Real-world example) We were called to a home in West Yorkshire where a 1.5m garden retaining wall had developed a dangerous lean after heavy rain. Our survey found the wall had no drainage and minimal footing. We designed a retrofit solution to relieve the water pressure and stabilise the wall, avoiding a full rebuild for the client. After an expert assessment, you’ll get a report of what’s wrong and a plan for a compliant fix. Remember, in the UK any substantial remedial work on a retaining wall over 1m should be done to meet Building Regulations, so professional guidance is key.
Improve Drainage Behind the Wall: Water management is often the simplest yet most effective fix. If your wall lacks drainage or the existing weepholes are clogged, upgrading drainage can immediately reduce pressure. Solutions include installing or clearing weep holes (small openings that let water through the wall). You might also add a perforated drainage pipe (often called a “French drain”) behind the base of the wall. This pipe, wrapped in gravel and filter fabric, collects water and redirects it away from behind the wall. Ensure any surface water (from gutters, driveways, etc.) is directed away from the top of the wall as well. Sometimes just extending a downpipe or regrading the slope can keep tons of water from ever reaching the wall. Good drainage is a low-cost measure that must accompany other fixes – otherwise, water will continue to undermine any repair.
Masonry Retaining Wall with Graded Backfill, Drain & Weep Holes Reinforce or Brace the Wall: For walls that are leaning or bulging but still salvageable, various reinforcement techniques can stabilise them:
Tie-backs / Anchors: These are steel rods or cables that are driven back into the stable soil behind the wall (sometimes 3-4 meters or more back). One end of the rod is attached to a plate or bracket on the front face of the wall, and the other end is anchored in the soil (either by a helical screw anchor or a concrete grout bulb). The rod is then tensioned to pull the wall toward the soil. This counteracts the outward pressure. Tie-back anchors can be very effective for concrete or masonry walls that have begun to tilt. A key advantage is halting further movement and restoring stability without having to dismantle the wall. A downside to this method is it requires specialist contractor input and can often be cost-prohibitive for small scale domestic works.
Historic Retaining Wall Stabilised with Soil Nails Geogrid Reinforcement: If you have a segmental block wall that’s shifting, one fix (short of rebuilding) is to excavate behind it and install geogrid layers. Geogrid is a high-strength polymer mesh that, when layered between the soil and connected to the wall, essentially turns the soil mass itself into part of the wall. It’s like extending the wall’s “footing” back into the slope. This method requires removing some of the backfill, adding geogrid at intervals, and recompacting. This can be disruptive but is cheaper than a new wall, especially if carrying out the labour yourself.
Geogrid Reinforcement Layer Concrete Buttresses or Shotcrete Facing: For a reinforced concrete wall that has cracked or started to deflect, one solution is adding strength to the wall itself. Buttresses are vertical concrete columns poured against the face or back of the wall to prop it up. Shotcrete (sprayed concrete) can be applied as a new continuous layer over the wall face, effectively creating a thicker wall. We might also embed steel reinforcement (rebar mesh) with the shotcrete to tie everything together. These approaches increase the wall’s capacity, though they will change its appearance (which might be fine for a hidden backyard wall, but maybe not for a front garden feature).
Stone Retaining Wall Reinforced with Buttresses
Strengthen the Foundation: If the wall’s footing or base is the issue (e.g. it’s sinking or rotating), you need to address the ground support:
Underpinning: This involves excavating sections below the wall’s foundation (in a staged manner to avoid collapse) and pouring new concrete footings or installing jacks to transfer the load to deeper, stronger soil. Underpinning can effectively give a shallow wall a deeper toe in the ground.
Mini Piles or Micropiles: These are small-diameter structural piles that can be driven or drilled at the base of the wall to provide extra support. For example, inserting a row of inclined mini-piles along the front of a leaning wall can help push back and hold it in place. Alternatively, mini-piles can support a new concrete beam that the wall is then tied into.
Soil Improvement: Sometimes the soil itself is too weak or prone to erosion (say, very loose sand or soft clay). Techniques like pressure grouting can be used – injecting cement grout into the ground behind and under the wall to solidify the soil. Another option is using geotextile fabric under the footing or in the backfill to improve load distribution.
Partial Demolition and Rebuild (Selective): If one section of the wall has clearly failed (say, a 3-metre stretch has collapsed or bulged), you might not need to rebuild the entire wall. Often, we identify a failing segment and carefully dismantle that portion back to stable connections. The rebuild would involve proper foundations and reinforcement in that area, effectively “patching” the wall to a higher standard. Key is to tie the rebuilt section properly into the old portions (using steel dowels or keying into the existing wall) so that it acts as one continuous structure. This approach balances cost and benefit: you spend more than a quick fix, but less than starting from scratch. However, if multiple sections (more than about one-third of the wall) are compromised, a full replacement might be more economical in the long run.
Throughout any stabilisation process, always keep safety in mind. If a wall is severely unstable, temporary bracing or even evacuating the area might be necessary during the work. For instance, we advised the use of temporary props and safety fences for a client in South Yorkshire where a tall retaining wall was at risk of imminent collapse, ensuring no one was hurt while a permanent solution was designed.
Balancing Safety, Compliance & Cost
When dealing with a failing retaining wall, you’ll need to make decisions that juggle safety, legal compliance, and budget. Here are some guidelines on how to balance these factors:
Safety First
If the retaining wall is in danger of collapsing, especially if it supports a structure (like a patio, driveway, or building) or could fall onto a public area, treat it as an emergency. Don’t delay action. A collapsing wall can cause injury and significant property damage. Unfortunately, we have seen countless examples of this, such as a brewery taproom in Leeds which had to close for months when a retaining wall suddenly and unexpectedly gave way during a storm [5], a retaining wall which collapsed onto a clients car, taking a another structure with it and collapsing the roof of a car-port.
In another example, we were called to a inspect a collapsed retaining wall which supported the rear gardens of a row of terrace houses. Luckily nobody was present during the collapse, but it is easy to see how such catastropic and sudden collapses like this could lead to serious injury or worse if left without repair.
If you notice serious movement in a wall, cordon off the area and get professional help immediately. We sometimes implement temporary shoring (like bracing the wall with timbers or steel supports) to reduce the immediate risk while preparing a permanent fix. Never gamble with a wall that is showing advanced failure, the cost of a collapse (or injury lawsuit) will far outweigh the cost of a prompt repair.
Regulatory Compliance (UK Building Regulations)
For walls retaining over 1 metre of ground, UK Building Regulations will apply in most cases. That means any solution should be designed or checked by a chartered structural engineer and, if required, approved by your local authority.
It’s not just red tape, it’s about ensuring the fix actually works and is safe. The law aside, following the standards is wise. LABC guidelines say walls over ~0.9m should have engineer design, because the higher the wall, the greater the danger if it fails. So even if your wall is just at that threshold, it’s worth doing things “by the book.” A good engineering firm (like Shepherd Gilmour) will handle the necessary calculations and provide drawings for council approval. We also make sure the design complies with relevant codes (British Standards or Eurocodes, and the principles in Approved Document A). Compliance ensures not only safety but protects you if you sell the property – an informally fixed retaining wall could raise flags in a survey.
Finally, if a retaining wall is also near a boundary, or forms part of a boundary its self, as is often the case, then it is necessary to comply with The Party Wall Act 1996, further details of which are provided at the bottom of this article.
Cost Considerations – Repair vs. Rebuild
Naturally, cost is a big factor. You want to fix the problem without breaking the bank. In many cases, reinforcing or repairing a wall is far cheaper than a full replacement. For context, we would estimate a full replacement of a retaining wall can typically cost 4-5 times as much as a repair. If the wall is mostly sound and only needs drainage, anchors, or a partial rebuild, it’s often wise to go that route. A reinforcement might extend the wall’s life by 10-20 years or more at perhaps a quarter of the cost of building a new wall.
That said, there are times when replacement is more cost-effective. If more than about 30-40% of the wall length is failing, the patchwork approach could end up costing nearly as much as starting anew, and you’d still have an old wall with potential inherent defects. We advise clients with widespread issues that a new wall (with proper design) might be the better long-term investment. We always aim to offer a solution that balances safety with your budget, sometimes an upfront bigger spend saves you from repeatedly paying for short-term fixes.
Risk Mitigation and Timing
Consider a phased approach if budget is tight. Address the most critical sections first (for example, install drainage and braces now to reduce deterioration, then plan a rebuild of a section next summer).
We often prioritise measures that reduce immediate risk, such as bracing a bulging wall or tarping a slope to keep water out, while design and funding for the final fix are arranged. Temporary drainage improvements (like quickly drilling a few weepholes or pumping out water behind the wall) can relieve pressure and buy time. Just remember, temporary fixes are not permanent – don’t “set it and forget it.” Check your insurance, some policies might cover preventative action if a collapse would damage insured structures, but they might not cover negligence if you knew the wall was failing and did nothing. From a risk perspective, acting sooner is almost always better.
How Shepherd Gilmour Can Help
At Shepherd Gilmour, we offer end-to-end expertise for retaining wall problems, from first inspection to final sign-off. Here’s what we bring to the table for homeowners, builders, and landowners dealing with a troublesome retaining wall:
Thorough Structural Surveys: Our engineers will conduct a detailed site survey to diagnose why your retaining wall is failing. We check everything – wall dimensions, material condition, drainage function, soil stability, and any additional loads. Using our long-standing experience, we can often pinpoint issues that others miss. You’ll receive a clear report outlining the failure mode (e.g. “wall rotating due to shallow footing on clay soil”) and our recommendations. This precise diagnosis is the crucial first step to a lasting solution.
Compliant, Cost-Effective Design: We provide engineered solutions that fully meet UK standards and local Building Regulations. Our designs are stamped by chartered engineers, which means you can submit them for Building Regs approval with confidence. We always strive to balance safety with your budget, exploring repair options before replacement, and designing efficiently so you’re not paying for unnecessary over-engineering. Whether it’s designing remedial drainage, specifying the spacing and depth of new abutments, or designing a brand-new retaining wall, our team will tailor the plan to your specific site and needs. The goal is a solution that is robust and economical.
Hands-On Project Management: Retaining wall fixes often involve multiple steps (groundwork, drainage installation, possibly obtaining permits, then construction). We can manage the entire process for you. This includes arranging any needed soil investigations (for example, soil bearing tests if we’re designing new foundations), preparing drawings for planning or listed building consent if required, and liaising with council inspectors. During construction, we can oversee the work to ensure the contractor follows the design (important for safety-critical elements like reinforcement or anchor installation). Essentially, we save you the headache and stress of the process, coordinating from start to finish so that the project runs smoothly and the wall gets fixed right first time.
Real Work Examples & References: We know trust is important which is why we’re happy to share case studies of similar projects we’ve completed on request. For instance, some of our recent examples include:
Stabilising the retaining wall of an existing period property by introducing stone faced buttresses & underpinning the foundations, as well as specifying remedial options for a 2m tall brick retaining wall which had begun to budge and crack, threatening the prospect of our clients proposed house extension. In both cases, we were able to preserve elements of the original stone and masonry façade for heritage aesthetics.
Aiding a commercial client in the Calder Valley stabilise an existing slope covered with trees subject to Tree Protection Orders (TPOs) in order to support a new development.
Design of a gabion wall to provide long-term stability to a new spillway in South Yorkshire.
These real-world examples demonstrate just the surface of our range of capability. Feel free to ask us for references or to visit past project sites where permitted or in the public realm, our work speaks for itself.
Ongoing Support & Maintenance: Our relationship doesn’t end when the immediate problem is solved. We’ll advise you on simple maintenance practices (like keeping those weep holes clear, or not planting water-heavy shrubs right behind the wall). We can schedule periodic inspections if desired – for example, an annual check-up on a wall that was reinforced, to ensure everything remains in order. And if you ever plan to alter the area (maybe terrace your garden or build near the wall), we can provide guidance so that your retaining structures continue to perform long-term. Think of us as your on-call structural consultants, always here to help with advice or rapid response if an issue arises.
At the end of the day, our mission is to safeguard your property and peace of mind. Retaining walls might not be glamorous, but they are critical to the integrity of your landscape and structures. We take pride in engineering solutions that stand the test of time, keeping you, your family, and your property safe.
In Summary
A failing retaining wall can go from a minor eyesore to a catastrophic collapse more quickly than many realise. The good news is that early intervention and proper engineering can rescue a wall in distress and prevent disaster. Keep an eye out for early signs – cracks, tilting, water leakage, or shifting soil and don’t ignore them. Understand that many walls fail due to basic issues like being too slender, lacking footings, or having no drainage. By applying practical stabilisation techniques (improved drainage, anchors/geogrid, better foundations, etc.) you can often extend the life of the wall and avoid the cost of a full rebuild.
Bottom line
If your retaining wall is showing trouble or if you’re even planning a new retaining wall, get experts involved sooner rather than later. It’s far cheaper and safer to fix problems when they’re small than after a collapse.
At Shepherd Gilmour, we’re ready to help – from the rugged rural countryside of Yorkshire, Derbyshire, Lancashire and Northumbria to urban city centres of Manchester, Leeds & beyond. We’ll evaluate your wall, design a proper solution, and see the project through to completion, all with a focus on safety, quality, and your budget. Don’t wait for that small crack to become a landslide. Contact us today to schedule a professional assessment of your retaining wall. We’ll help you reinforce your wall, and your peace of mind, for years to come.
Get in touch with our team at Shepherd Gilmour for expert retaining wall advice or a quote. We’re here to ensure your wall retains your trust. Stay safe!
Citations
Useful Reading
1.Guidance on retaining wall responsibilities - Bradford Council https://www.bradford.gov.uk/transport-and-travel/highways/guidance-on-retaining-wall-responsibilities/
2.Retaining Walls - Designing Buildings, the Construction Wiki https://www.designingbuildings.co.uk/wiki/Retaining_walls
3.Retaining Wall Basics - LABC* https://members.labc.co.uk/member-news/retaining-wall-basics
4.Party Wall Explanatory Booklet - UK Government https://www.gov.uk/government/publications/preventing-and-resolving-disputes-in-relation-to-party-walls/the-party-wall-etc-act-1996-explanatory-booklet
*Note members access may be required.
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