Retaining walls are important structures that prevent soil erosion and provide support for landscapes. However, retaining walls can deteriorate over time and may need repairs to remain functional. Here is a comprehensive guide on how to repair a retaining wall.
Inspect the Retaining Wall to Determine Needed Repairs
The first step is to thoroughly inspect the retaining wall to identify any issues. Look for:
- Cracks, bulges or leaning – This indicates structural instability.
- Deteriorating or missing mortar – Mortar keeps bricks or blocks together.
- Water damage – Standing water, stains or vegetation can cause deterioration.
- Poor drainage – This causes water pressure buildup behind the wall.
- Damaged or eroded soil behind the wall – Improper backfill allows wall movement.
- Damaged or eroded footer – Undermines the wall’s foundation.
Take notes on all visible issues to determine the necessary repairs.
Make Repairs to Settled or Leaning Walls
If the retaining wall is leaning or has settled unevenly, it likely requires rebuilding.
- Remove soil behind the wall to reduce pressure. Shore up leaning sections for safety.
- Dismantle settled or unstable portions of the wall. Salvage bricks/blocks that are in good shape.
- Excavate behind the dismantled section to access the footer. Repair or add to the footer as needed to stabilize the wall.
- Rebuild the dismantled section on the repaired footer using new building materials as needed. Follow best practices for assembly.
- Backfill with properly graded gravel and compact in layers. Add a drainage system.
Rebuilding settled sections restores structural integrity. Proper soil management and footer support prevents re-settling.
Repoint Mortar Joints
Missing or deteriorated mortar allows moisture intrusion and destabilizes the wall.
- Use a chisel or roto-hammer to remove loose mortar to a depth of 1⁄2”. Sweep away debris.
- Mix new mortar to match the original strength and color. Aim for a drier consistency.
- Dampen the brick or block surface to prevent moisture loss from new mortar.
- Push new mortar into joints in thin layers. Compact each layer thoroughly before adding more.
- Fill joints until flush with the brick/block face. Smooth with a jointing tool for a neat finish.
- Keep the wall protected for 48-72 hours while new mortar cures.
Proper repointing seals out water and restores structural integrity.
Patch Cracks with Epoxy
For small cracks up to 1⁄4” wide, use epoxy injection to seal out moisture.
- Start by sealing the crack face with surface-mount epoxy to contain the injection epoxy.
- Drill angled holes into the crack at intervals along its length.
- Pump epoxy adhesive into the backside of the crack through the injection ports. Move from bottom to top.
- After injection, fill drill holes with surface-mount epoxy.
Epoxy bonds tenaciously to concrete and masonry. Cracks filled with epoxy are extremely durable repairs.
Install Filter Fabric and New Drainage
Poor drainage leads to buildup of excess hydrostatic pressure behind retaining walls. To improve drainage:
- Excavate behind the wall to expose the drainage gravel layer. Inspect gravel condition.
- Install non-woven geotextile filter fabric against the back of the wall, overlapping seams.
- Replace drainage gravel if needed. Grade for proper runoff flow.
- Install 4” perforated PVC drainage pipes at the base, sloped to daylight or a catch basin.
- Backfill with more drainage gravel, covering pipes.
Proper drainage prevents moisture issues and relieves pressure on the retaining wall.
Backfill Properly with Gravel
Wall movement often results from improper soil backfill. Use these guidelines:
- Completely remove organic topsoil from the area behind the wall.
- Backfill in thin, compacted layers with dense graded aggregate like road base.
- Slope backfill away from the wall at 1/4” per foot minimum.
- The final 12” beside the wall should be gravel only, no soil.
- Install filter fabric between the final backfill layer and retained soil.
Proper soil type and compaction technique keeps the rebuilt wall stable.
FAQ
How do I determine if my retaining wall needs repair?
Inspect for signs of deterioration like cracks, bulges, missing mortar, water damage, soil erosion behind the wall, and damaged footers. Any of these point to the need for repairs.
What kind of mortar should I use when repointing?
Use a mortar mix that matches the compressive strength of the original. Type S or Type N mortar is best for retaining walls. The color should also match the original mortar.
Can I use concrete instead of mortar?
Mortar is recommended, as it provides some flexibility to allow for minor wall movement. Concrete would be too rigid. Use concrete only for major footer repairs.
How long does injected epoxy last when repairing cracks?
Epoxy bonds permanantly to concrete and masonry. Cracks repaired with epoxy injection should remain sealed indefinitely provided the epoxy penetrates all the way to the backside.
Should filter fabric be used when backfilling with gravel?
Yes, filter fabric contains the gravel but allows water drainage. This separation keeps soil from migrating into the gravel over time.
How often should retaining walls be inspected?
Inspect retaining walls at least once per year, ideally in the spring. Look for signs of new cracking or deterioration. Early detection allows smaller repairs before major problems develop.
Conclusion
With proper inspection and timely repairs, retaining walls can be restored and maintained to provide many more years of service. Addressing issues like deterioration, cracks, soil erosion, drainage, and footer damage restores structural integrity and prevents further damage. Patience and using the right materials like quality mortar and epoxy makes DIY repairs possible in many cases. Consider contacting a professional when in doubt. With some effort, your landscape can continue to benefit from a sturdy, long-lasting retaining wall.