Fixing or replacing your retaining wall

Is your retaining wall starting to look a little iffy, but you’re not sure whether it needs to be replaced completely or simply repaired? Retaining walls provide structural support and prevent soil erosion. However, broken or unsafe retaining walls can pose serious risks. If you’re noticing cracks, crumbling, or other signs of damage, you may need to either fix your retaining wall or potentially replace the retaining wall altogether.

We’ll walk you through how to tell whether repairing or replacing a retaining wall is more applicable for your property and guide you on the best approach to restoring the integrity and safety of this vital landscape feature.

When to fix your retaining wall

Keeping a keen eye out for warning signs is crucial to addressing retaining wall issues before they escalate. Depending on the type and material of the retaining wall, you’d see these typical signs:

• Timber: Signs of rot, warping, and damage from insects like termites
• Concrete: May exhibit cracking, crumbling, or displaced stones
• Brick and mortar: Can develop cracks and deterioration over time

One of the most concerning indicators is an entire section of the wall leaning or buckling. This signals an underlying structural problem that requires prompt attention. If you notice a section starting to lean, it’s time to call a professional to remove any excess soil, inspect the wall’s fortification, and ensure it’s still secure and stable.

When to repair your retaining wall

While you can address some retaining wall issues yourself, there are scenarios where a full replacement is better. Structural failure, such as significant cracking, crumbling, or leaning, indicates that the wall’s integrity has been compromised beyond simple fixes. Likewise, widespread and severe deterioration, like extensive rotting in timber walls or major loss of mortar in masonry, may require a complete overhaul.

The risks of attempting a DIY retaining wall replacement may lead to further damage, safety hazards, and even catastrophic failure down the line. It’s better to consult an expert who can assess the wall’s condition properly, give you pointers on what you should do or need to obtain to get started with replacing a retaining wall and recommend a suitable course of action.

How to fix your garden retaining wall

As with most general repair work, the first step is to figure out whether you have a problem early on. If you’d like to know how to fix a retaining wall yourself, here are a few tips:

For cracked walls

• Determine the cause of the cracking: Assess whether the cracks are a result of minor superficial issues or indicate a more serious structural problem. Minor cracks can often be repaired, but widespread or deep cracking may require professional assistance.
• Clean the affected area: Use a stiff brush to remove any loose debris, dirt, or vegetation from the crack. This will ensure the repair material adheres properly.
• Apply a concrete repair compound: Look for a high-quality concrete patching compound or epoxy filler specifically designed to repair masonry cracks. Follow the manufacturer’s instructions.
• Smooth the surface: Once the repair compound has cured, use a trowel or putty knife to smooth the surface and blend it into the surrounding wall.
• Allow sufficient drying time: Resist the temptation to put the wall back into service immediately. Follow the recommended curing time to ensure a strong, long-lasting fix.

For crumbling mortar

• Identify the extent of mortar deterioration: Inspect the wall to determine how widespread the crumbling mortar is and gauge the scope of the repair work required.
• Carefully remove loose debris: Remove any loose, crumbling mortar using a chisel or masonry drill without compromising the surrounding bricks or stones. Take care not to damage the existing wall structure.
• Prepare the joints: Use a stiff-bristle brush to thoroughly clean the joints, removing any remaining dirt or debris. This will ensure optimal adhesion for the new mortar.
• Mix and apply new mortar: Prepare a batch of new mortar, matching the original composition as closely as possible. Use a pointing trowel to press the mortar into the cleaned joints for a seamless finish.
• Cure the new mortar: Allow the freshly applied mortar adequate time to cure. Avoid disturbing the wall during this period.

For rotting timber

• Inspect the extent of timber damage: Carefully examine the retaining wall to identify all sections with rot, warping, or other signs of deterioration.
• Remove damaged wood: Using saws, chisels, and other tools, remove any rotted or warped timber boards. Dispose of the damaged material properly.
• Prepare the area: Clean the wall cavity where the new timber will be installed, removing any dirt, debris, or residual rot.
• Install new treated timber: Replace the damaged boards with new, preservative-treated lumber. Secure the new boards to the existing wall structure.
• Seal and protect the new timber: Apply a suitable wood sealant or preservative to the new boards to protect them against future moisture and rot.

Whatever repairs you undertake, you’ll likely have to displace the soil and plants behind your retaining wall. The last thing you want is pressure from the soil, pushing your wall over entirely while it’s at its weakest during the repairs.

Retaining walls handle a lot of wear and tear, so they may need replacing periodically. If your builder has determined that your retaining wall has reached the point where it’s past repair, then it’s best to remove it and install a new one.

Replacing your garden retaining wall

When your retaining wall has reached the end of its life, a complete replacement is often the best solution. This involves a series of steps, and you’ll need a professional builder to help execute these:

Take down the old wall

The first step in replacing your existing retaining wall is to dismantle and remove the existing wall. This might involve using specialised tools and equipment to safely lift and remove the materials, whether it’s timber, concrete, brick, or stone. During the removal process, temporarily shore or brace the soil behind the wall to prevent it from collapsing or causing further damage.

Build a solid foundation

With the old wall gone, you’ll need to prepare a strong foundation for the new one. This might involve excavating and compacting the soil, installing drainage systems to prevent water build-up, and creating a level base for the new wall. A professional can help ensure the foundation can handle the weight and pressure of the new retaining wall, accounting for soil conditions and the wall’s height.

Construct the new wall

Depending on the materials you choose, this could involve laying concrete blocks, stacking stone, or securing timber beams. The new wall needs to be built with precision and expertise to ensure it’s structurally sound and long-lasting, so make sure to call your local builder to help you out with the project.

Why you should hire a professional to do the job

Here are some reasons why hiring a professional landscaper or builder for retaining wall work is a wise choice:

• Site assessment: A professional can thoroughly evaluate the site conditions, soil composition, and wall requirements to engineer a safe and structurally sound solution.
• Material selection: They can recommend the most suitable materials (e.g. concrete, stone, timber) based on your landscaping budget, and long-term performance needs.
• Adherence to building codes: They build the retaining wall to meet local regulations and safety standards, which is helpful if you need a building inspection report.
• Hassle-free project management: Professionals handle all aspects of the project, from obtaining necessary permits to overseeing construction, ensuring a hassle-free experience.
• Cost optimisation: The cost to replace a retaining wall isn’t cheap, but professional expertise can help identify cost-effective approaches and prevent expensive mistakes that often plague DIY projects.
• Warranty and ongoing support: Many professional landscapers offer guarantees on their work and can provide maintenance tips to preserve the retaining wall’s condition.

Fix or rebuild a solid retaining wall

Maintaining a solid and secure retaining wall is crucial for the long-term viability and visual appeal of your outdoor spaces. By addressing issues promptly and enlisting qualified landscaping experts, you can ensure your retaining wall continues to provide the necessary structural support and erosion control.

Don’t let a troubled retaining wall become a problem—take control of your landscape’s stability and let it protect your property.

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FAQs on retaining wall

Can I use concrete to fix a retainer wall?

Yes, concrete is an effective way to repair minor cracks and crumbling in retaining walls. Look for concrete patching compounds or epoxy fillers designed specifically for masonry repair.

However, for more extensive damage or structural issues, it’s best to consult a landscaping professional who can recommend the most suitable course of action, including replacing a retaining wall.

Do I need council approval to replace a retaining wall?

In most cases, yes. Replacing a retaining wall is generally considered a building work project in Australia, which requires approval from your local council. This ensures the new wall meets safety standards and building codes. Check with your council about the specific permit requirements before starting any retaining wall replacement work.

Can you build a new retaining wall in front of an old one?

While it is possible to construct a new retaining wall in front of an existing one, replacing an existing retaining wall this way is generally not recommended. Building a second wall can create additional soil pressure and drainage issues that could ultimately undermine both structures.

A better solution is to completely remove the old wall and build a new one designed to support the landscape properly. Again, it is advisable to consult a professional to determine the appropriate action.