Are you about to purchase a property and have noticed cracks on one or more of the retaining walls?
Retaining walls are structural features designed to hold back soil and rocks. They can be used to provide usable land on sloped blocks, support a basement design built into a hill, slow the rainwater flow or help to slow downhill erosion that could otherwise threaten your home’s foundations. They’re often made of timber, concrete, or stone, timber being the least expensive option. As a result, they play an important role in your house design, and any crack or movement should be carefully monitored.
In this article, we’ve put together a few pointers to help you understand where these cracks or movements come from and what can be done about them.
Common Cause for Retaining Wall Cracking and Movement
Trees
Having trees in your garden and particularly close to the borders can be a great way to get some privacy while embellishing your outdoor space. Big, beautiful trees can also provide shade in summer, clean air, and add value to your property as part of a manicured garden. Yet, they can also cause some severe damage to your retaining walls, requiring thousands of dollars to fix. Indeed, planting large trees close to retaining walls can lead to wall deterioration as the extra pressure from the tree roots creates cracking or wall movement.
Therefore, if you’re looking to buy a property that has big trees close to retaining walls, make sure to factor in the cost of engaging an arborist to further investigate and advise. This will save you a lot of hassle down the road!
Poor Design and Drainage
Inadequate footing or reinforcement design is one of the most common causes of retaining wall movement. Indeed, inadequate footing or anchoring can lead to your retaining wall bulging out or tipping forward.
Rainwater and moisture are also another common culprit. Indeed, water or moisture building up behind your retaining walls can put immense pressure on it. Therefore, you need to ensure adequate drainage to avoid having to spend a lot of money on fixing or replacing your retaining wall later down the track.
Note that to be durable and efficient, retaining walls require subsurface drainage along the bottom, outlet points, and weep drains at appropriate intervals.
Termite Activity
Retaining walls and build sleepers used to build retaining walls are prone to termite infestation. A retaining wall can be extremely costly to replace, so if the property you’re interested in features old timber sleeper retaining walls, you should acquire the services of a pest inspector before purchasing it. They’ll be able to assess termite activity and come up with a plan.
Fixing Retaining Walls
If the damage to your wall is not too severe, leave as is and regularly monitor for additional movement.
Improve the drainage: as mentioned above, poor drainage can cause your retaining wall to crack or move due to the pressure of trapped water and moisture building up behind the wall. Therefore, enhancing drainage around the wall could be a good way to make your wall last longer.
Another way to relieve the pressure on the retaining wall is to remove part of the soil or lower the soil behind the wall
Reinforce the existing wall: depending on the extent of the damage and where the issue comes from (lack of vertical steel rods, not enough steel, etc.), you should get in touch with a structural engineer. You’ll be able to ask them for advice and see whether the wall can be reinforced instead of having to replace it entirely.