Retaining Wall Materials: Concrete Block vs. Timber vs. Stone

The material you choose for a retaining wall determines everything downstream: how much it costs, how long it lasts, whether you can build it yourself, and how much drainage work is required behind it. A concrete block wall and a timber wall might look similar in a photo, but they behave very differently over time — and one of them will be gone in 15 years.

Once you've picked a material, the retaining wall calculator handles block counts, gravel backfill, and cost estimates for your dimensions. If you already know what you want and just need quantities, jump to the calculator at the bottom.

Quick Comparison

Interlocking Concrete Blocks

Segmental retaining wall (SRW) blocks are the dominant DIY retaining wall material for good reason. They are engineered specifically for this application — each block has a rear lip that creates a natural batter (backward lean) as you stack courses, which shifts the wall's weight into the hillside and improves long-term stability without mortar or math.

How They Work

Blocks interlock and set back slightly with each course, creating a gravity wall that resists soil pressure through mass and geometry. Standard residential walls under 4 feet use this method without pins, mortar, or geogrid. Walls taller than 4 feet on poor soils typically need geogrid reinforcement extending back into the hillside — at that point, you're looking at an engineered design and likely a permit.

Pros

• No mortar, no special tools — installable by most homeowners
• Engineered block geometry handles drainage and structural forces better than stacked timber or random stone
• 50+ year lifespan with proper drainage
• Wide variety of textures and colors — smooth, tumbled, split-face, fieldstone-look
• Widely available at home improvement stores and masonry suppliers
• Can be disassembled and rebuilt if you make a planning mistake

Cons

• Heavy — standard blocks weigh 25–80 lbs each. A 20 ft × 3 ft wall involves moving 3,000–5,000 lbs of blocks
• Requires a compacted gravel base — can't just set on bare dirt
• Not ideal for very curved or irregular walls — the block shape wants straight or gently curved runs
• Most block lines have a distinct manufactured look — not everyone wants that aesthetic

Drainage Requirement

All retaining walls need drainage behind them — concrete block especially, because the tight face doesn't let water weep through. The standard approach is 12 inches of ¾-inch crushed stone directly behind the blocks, backed by non-woven geotextile fabric to keep soil from migrating into the drainage zone. For walls over 20 feet long or in high water-table areas, a perforated drain pipe at the base of the gravel is worth adding — see the French drain guide for pipe sizing and slope requirements.

Use the gravel calculator to estimate backfill volume for your specific wall dimensions.

Cost

Standard concrete blocks run $1.50–$5.00 each at big-box stores; premium brands like Allan Block cost $2.50–$4.00 for their Classic line. For a typical 20 ft × 3 ft wall, expect $200–$500 in blocks plus $100–$200 in gravel, fabric, and adhesive. See the full cost guide for size-based estimates. For Allan Block specifically, the Allan Block calculator covers exact block counts and pricing for AB Classic, Junior, and Europa.

Timber and Landscape Ties

Timber retaining walls use horizontally stacked landscape timbers or railroad ties. They're the second most common DIY choice — easier to cut with a chainsaw than to chip concrete, and forgiving of slightly uneven ground. But the lifespan issue is real and worth understanding before you commit.

Timber Types

• Pressure-treated landscape timbers: The standard residential choice. 6×6 or 8×8 lumber treated with copper-based preservatives (CCA was phased out; modern PT uses ACQ or CA). Rated for ground contact, but the treatment only penetrates the outer layer — once cut ends are exposed to soil, rot accelerates.
• Railroad ties (reclaimed): Larger (7×9 in), heavier, and treated with creosote — a coal-tar based preservative that is effective but can leach into soil and is considered a potential carcinogen. Increasingly hard to source, and banned from some residential applications. Check local regulations before using.

Pros

• Easier to cut to fit — a circular saw or chainsaw handles most cuts
• Lower material cost than concrete block on a per-square-foot basis
• More forgiving of slightly irregular base grading
• Natural wood appearance works well in informal garden settings
• Can be used for low terracing and raised bed borders

Cons

• Lifespan: Pressure-treated timber in ground contact lasts 10–15 years before rot becomes structural. Railroad ties may last longer due to creosote, but sourcing and regulations are limiting. Plan to rebuild.
• Requires deadmen or tie-backs for taller walls: A timber wall over 2 feet tall needs horizontal timbers extending back into the hillside every few courses to prevent leaning. This adds material and labor.
• Creosote railroad ties can leach into soil — not appropriate for vegetable gardens or areas where children play
• Prone to movement with frost heave in cold climates unless well-drained

Best Use Cases

Low terracing in garden areas (under 2 feet), raised bed borders, informal backyard steps, situations where you expect to reconfigure the layout in 10 years anyway. Not recommended for walls over 3 feet, high-traffic areas, or anywhere the wall failure would cause a significant problem.

Natural Stone (Dry Stack)

Dry-stack stone walls are built without mortar — stones are fit together and rely on gravity, weight, and the slight backward lean of the wall face for stability. Done well, they're the most visually striking option and effectively last forever. Done poorly, they shift and topple.

Stone Types

• Fieldstone: Rounded or irregular stone, often sourced locally. The hardest to stack because no two pieces are alike — takes time to find pieces that fit together tightly.
• Flat flagstone / ledge stone: Flat-ish stones that stack more predictably. Limestone, sandstone, and bluestone are common choices. Much easier to work with than round fieldstone.
• Cut stone / ashlar: Quarried and cut to regular dimensions. Expensive but stacks cleanly and has a formal look. Closest to block in terms of consistent dimensions.

Pros

• 50–100+ year lifespan — many dry-stack stone walls built 100 years ago are still standing
• Natural, organic aesthetic that improves with age and moss/lichen growth
• The irregular face naturally allows some water weeping — drainage requirements are less critical than with solid block faces
• Can be rebuilt or repaired stone by stone without demolishing the whole wall
• No special materials needed — just stone, a base, and patience

Cons

• Most labor-intensive: Fitting irregular stone takes significantly longer than stacking engineered blocks. Expect 2–3× the labor time versus block on the same wall size.
• Most expensive material option at $8–$15/sq ft for the stone alone
• Requires skill to build a stable dry-stack wall — incorrect batter angle or poor stone selection causes settling and leaning
• Natural stone is heavy and difficult to source reliably — availability and pricing vary significantly by region
• Low walls look great; taller stone walls require engineering and are generally contractor work

Best Use Cases

Decorative low walls (under 2 feet), cottage or woodland garden aesthetics, situations where you have a local stone source, property owners who want a permanent structure and are willing to invest the time or hire a mason. Not the right call for a weekend DIY project on a tight budget.

Poured Concrete

Poured concrete or reinforced concrete masonry unit (CMU) walls are the strongest retaining wall option and the standard for walls over 4 feet, commercial applications, and any situation where failure isn't an option. They are also firmly in contractor territory for most homeowners.

A poured concrete retaining wall requires formwork, steel rebar reinforcement sized to the wall height and soil pressure, and either a concrete truck or several days of mixing. The engineering involved — footing depth, wall thickness, rebar schedule — is not guesswork, and an incorrect design fails catastrophically rather than gracefully.

When It Makes Sense

• Walls over 4 feet where an engineer is already involved
• Below-grade basement walls or foundation retaining applications
• Commercial or municipal projects with specific load requirements
• Situations where a thin profile is needed — poured concrete can be thinner than stacked block for the same structural capacity

For DIY projects under 4 feet, there is almost never a reason to choose poured concrete over interlocking block — block is faster, doesn't require forms, and costs about the same at residential scale. See the concrete cost guidefor current material pricing if you're costing a poured option.

Gabion Baskets

Gabion walls are wire mesh baskets filled with stone, stacked and tied together to form a wall. They're common in civil engineering and erosion control applications and have made inroads in residential landscaping over the past decade — partly for their industrial-modern aesthetic, partly because they handle drainage inherently well.

Pros

• Excellent drainage — water moves through the stone fill freely, which eliminates hydrostatic pressure buildup
• Flexible structure tolerates minor ground movement without cracking
• Can use local stone for fill, which offsets basket material cost
• 50+ year lifespan if galvanized or PVC-coated baskets are used
• Distinctive aesthetic — works well in contemporary and industrial landscapes

Cons

• Requires a large volume of stone fill — all that stone needs to come from somewhere, and sourcing and hauling it adds to the project cost
• Wire baskets are a commodity but quality varies — cheap baskets with thin galvanizing rust through in 10–15 years. Specify heavy-gauge galvanized or PVC-coated mesh.
• Bulkier than block — a gabion wall takes up more footprint than a block wall holding the same grade
• Not the right look for traditional or formal landscapes

Best Use Cases

Erosion control on slopes, contemporary landscape design, situations where drainage is a primary concern, larger projects where stone can be sourced locally at low cost. Less common for small residential walls where block is simpler and cheaper to install.

Drainage: The Common Requirement

Regardless of which material you choose, every retaining wall needs drainage behind it. Water pressure — not soil pressure — is the primary cause of retaining wall failure. A wall that holds the same soil without drainage will push outward and eventually fail, while a well-drained wall of the same design can last decades.

The standard drainage approach for residential walls:

• Gravel backfill: 12 inches of ¾-inch clean crushed stone directly behind the wall. Do not use pea gravel (it migrates) or native soil (it holds water and expands).
• Geotextile fabric: Non-woven landscape fabric placed between the native soil and the gravel backfill prevents soil from migrating into the drainage zone over time. This is the step most DIY builders skip and later regret.
• Drain pipe:For walls over 20 feet long, or on sites with a high water table, a 4-inch perforated pipe at the base of the gravel — sloped to daylight at the wall's end — ensures water has an exit point even in heavy rain events. The French drain calculator covers pipe sizing and gravel quantities for this application.

Use the gravel calculator to calculate your backfill volume. Natural stone and gabion walls are somewhat self-draining through their faces, but the gravel-backfill approach still improves performance and reduces soil pressure regardless of material.

If the site has an existing drainage problem that contributed to the grade issue, address that before building the wall — see the fill dirt guide for grading and French drain planning for redirecting water away from the wall zone.

Which Material Is Right for Your Project?

Estimate Your Material Quantities

Once you've settled on a material, use the calculator below to get block counts, gravel backfill volumes, and a cost estimate for your wall dimensions. For Allan Block specifically, the Allan Block calculator guide has coverage tables for AB Classic, Junior, and Europa blocks. For the full step-by-step build process, see how to build a retaining wall. For a complete cost breakdown by material and wall size, see the retaining wall cost guide.