What Does a Retaining Wall Do?
Retaining walls hold up soil that would otherwise slide away, helping the landscape maintain its shape and making the space in front of it usable for walking, sitting or gardening. It’s usually necessary for areas near soil fault lines or water runoff causing hillside erosion. A retaining wall protects foundations by preventing the loss of supporting soil or pressure from accumulation of sliding soil. Adding a retaining wall improves the look and property value of your home.
What Affects Cost
It’s difficult to estimate the cost of constructing a retaining wall because a lot depends on what the landscape itself requires. For all good retaining walls, site preparation involves digging footings, laying landscape fabric, replacing soil, backfilling with gravel, and installing drainpipes. As the wall is being built, it will need to be anchored it into the hillside and the soil behind it will be compacted. How much labor, material, and engineering will be needed can only be calculated using specific knowledge of the site.
- Site preparation – Some areas may require extensive engineering, preparation, and reinforcement. Areas of expansive soils or bedrock can drive up excavation costs and foundation size. For example, clay soils would need to be removed because they hold on to water.
- Area weather – Extreme weather or earthquake risk may require more extensive structural reinforcement and/or waterproofing.
- Project size – Retaining walls must be short because they’re under enormous pressure and can’t be taller than 3-4 ft. It will cost your more if you need to build more than one level of wall for structural integrity. Additions like seats, steps or pilasters also cost more.
- Material cost – You have some choice when it comes to building materials. Wood is the cheapest – but also lasts the shortest.
- Access to building site – Limited access to the location of the wall due to narrow passageways can require extensive labor when it comes to making deliveries of stone by hand or transporting fill material.
The most common types are interlocking timber blocks, stacked stone, brick or block, concrete. Don’t be afraid to think outside the box! This wall should be a long term addition to your home.
- Add a seat wall, steps or pilasters.
- Incorporate the natural landscape, with large or lichen-encrusted boulders.
- Poured concrete retaining walls have a smooth sleek and modern look, while still being cost effective.
- Use a hewn stone cap to overlay the building material. You can add different colors geometric patterns.
- Jogged retaining walls break up the shape into a zigzag pattern of connected l-shapes. They can also be more functional if you use the area for sitting.
- Break the retaining wall into tiers of shorter walls for a regal look and better engineering.
Make Your Investment Last
The easiest choice to guarantee longevity is to choose a good material. Masonry lasts longer than wood! Make sure you get quality masonry and be wary of a material that chips or breaks easily. Plan out deliveries to the best of your ability and don’t be afraid to exchange a product if it was damaged before you received it.
The three most common causes for failure are soil saturation, frost heave, and blowout. All involve an increase in pressure against the wall until it breaks. Soil saturation and frost heave both relate to poor water drainage. Soil saturation can be prevented by replacing soil and installing proper drainage. In the case of frost heave, pressure also comes from the water expanding as it freezes. To prevent it, the wall needs a properly dug footer below the frost line. Both issues can easily be prevented when done properly by a professional.
Wall blowouts can also be caused when a load is added within three feet of the top of the wall. It’s important to communicate with your builder if you’re planning on adding a shed or parking cars in the nearby area. This allows the builder to increase the strength by adding to the weight of the footer, or the number of tiebacks. It’s important to avoid a problem that will need the wall to be excavated, dismantled, or reengineered – all of which is very costly.
The materials involved are very expensive, so don’t DIY. The best way to guarantee you’re making a good investment in a garden retaining wall is to use professional help. It may seem like a simple stone wall, but aside from laying stone, building a retaining wall takes a lot of calculation, soil knowledge and site preparation to make it last. Contact us for more information or request an estimate to get you started on your project.