How Much Does a Retaining Wall Cost?
— How Much Do You Need?

A retaining wall is a structure built to hold back soil on a slope or hillside, or to create a level surface in a yard where the ground would otherwise erode, shift, or slide. You'll find them everywhere from backyard landscaping projects to highway embankments and commercial construction sites. What most people don't realize until they're mid-project is that the wall itself is only part of the story. Building one that holds up over time requires two distinct types of aggregate working together beneath and behind the structure. The first is a base or footing material, which is compacted crushed stone that creates a firm, level foundation for the bottom course of your wall. Without a solid base, the wall starts uneven and only gets worse as height is added. The second is drainage backfill, which is clean crushed stone placed directly behind the wall to let water flow through freely rather than pool and build up pressure. This drainage column is often what separates a retaining wall that lasts decades from one that leans or cracks after a few wet seasons. Hello Gravel supplies both types of aggregate in bulk, delivered by the truckload to your project site. Use the calculator on our site to get a quantity estimate for your specific wall dimensions, or reach out to our team if you want help thinking through what your project needs.

Gravel, without question. This is one of the most important decisions you'll make for the longevity of your wall, and it's worth understanding why. When soil gets saturated with water, it becomes dense and heavy. That weight pushes directly against the back of your wall, creating what engineers call hydrostatic pressure. Over time, that force can cause even a structurally well-built wall to tilt forward, crack at the base, or fail outright. Clay soils are especially problematic because they hold onto water for a long time and expand significantly when wet. Clean crushed stone works completely differently. Water moves through the gaps between the stones and drains away quickly rather than pooling against the wall face. A drainage column of gravel about 12 inches wide, running the full height behind your wall, dramatically reduces the pressure your wall has to fight against. At the base of that drainage column, a 4-inch perforated drain pipe wrapped in filter fabric helps carry water away from the wall footing entirely. Your gravel backfill funnels water down to that pipe, and the pipe routes it away from the structure. The difference in material cost between using proper drainage gravel and using excavated soil is relatively small. The difference in how long your wall lasts is enormous. Hello Gravel carries clean crushed drainage stone by the truckload. Use the calculator on our site to figure out how much your wall requires, or contact our team and we'll walk through the numbers with you.

Poor drainage is the single most common reason retaining walls fail. It is not a glamorous answer, but it accounts for the vast majority of leaning, cracking, and collapsed walls. Here is what happens when drainage is neglected: rain soaks into the soil behind the wall. That soil becomes saturated and starts to weigh significantly more than dry soil. The lateral pressure pushing against the back of the wall increases beyond what the structure was designed to handle. The wall begins leaning forward, the base shifts, and eventually the whole thing gives way. An inadequate footing is the second major failure point. If the base gravel was not compacted firmly, or if the trench was not dug deep enough to anchor the wall properly, the structure has no stable platform to work from. Every course of blocks above it amplifies the problem. Using the wrong backfill material is the third culprit. Fill dirt, clay, and organic-rich soil all retain water and settle unevenly over time. Neither is something you want packed against a wall you're counting on to hold a hillside in place for years. Addressing all three of these failure points comes down to using the right aggregate in the right places. A properly compacted base material gives the wall a firm, level foundation. A clean drainage stone backfill column lets water escape freely. Together, they are the foundation of a retaining wall that actually holds. If your wall project is coming up, Hello Gravel can get you the base material and drainage stone you need, delivered on the date you choose.

You want clean, angular crushed stone for the drainage column behind your wall. Both of those words matter. "Clean" means the stone contains no fine material, dust, or soil mixed in. Fines are tiny particles that settle into the spaces between stones over time, clog the drainage voids, and eventually slow or stop water movement. Once the drainage column stops draining freely, you lose the main benefit of having it. "Angular" refers to the shape of the stone. Angular crushed aggregate has rough, jagged edges from the crushing process. Those edges interlock under pressure and resist shifting, which adds a degree of structural stability to the drainage column. Round stones like natural river gravel can migrate and shift under load, which is less ideal. Common sizes that work well for retaining wall drainage include 3/4-inch crushed stone and other similar clean angular aggregates available through Hello Gravel. What you want to avoid for the drainage backfill is crusher run or any blended base material that includes fines. These products compact tightly, which makes them excellent for road bases and wall footings, but that same tightness prevents them from draining. Using a compactable base material in your drainage column because it was cheaper or easier to get is a trade-off that can cost you the entire wall later on. For the footing itself, a compactable dense-grade crushed stone is exactly what you want. It is the one place in your retaining wall build where tight compaction is the goal. The Hello Gravel team can help you identify the right materials for both parts of your build. Reach out or start with the calculator on our site.

The 1/3 rule is a widely used construction guideline that says roughly one-third of your retaining wall's total height should be buried below the finished grade. So if you want a wall that rises 3 feet above ground level when the project is complete, the total wall height including the buried anchor section should be around 4.5 feet, with about 1.5 feet below the surface. Think of that buried section as the wall's anchor. It resists the lateral pressure of the soil pushing against the back of the wall and keeps the base from sliding forward. Leave it out, and the wall is essentially sitting on top of the ground with nothing holding it in place. The practical impact on your material order is real. Every foot of wall that goes underground requires a properly prepared trench filled with compacted crushed stone to create a firm, level footing for the first course. That base layer is typically 4 to 6 inches of compacted aggregate, and the trench is usually a bit wider than the wall itself to give you room to work. For a 60-foot-long wall where the buried section is 1.5 feet deep, you are digging a trench along that entire length. A 4-inch compacted base layer in a 2-foot-wide trench over 60 feet comes out to roughly 1.5 to 2 cubic yards of footing material. Your actual numbers will vary based on wall length, footing depth, and trench width, so plug your dimensions into the Hello Gravel calculator for a more precise estimate before you order.