Brick retaining walls shape hillside yards into usable terraces, and a properly built wall lasts 50 to 100 years with minimal maintenance. Planning a brick retaining wall is more than stacking bricks; you need a concrete footing, internal drainage, tiebacks for taller walls, and in many jurisdictions a permit. This guide walks through design, materials, construction steps, and the common mistakes that cause walls to bulge, crack, or topple within 5 years.
Sizing and Permit Rules
Most US municipalities require engineered plans and a permit for any retaining wall over 3 to 4 feet tall, measured from the base of the wall to the top. Walls under that height usually need no permit but still must follow basic drainage and setback rules. Call your local building department before purchasing materials.
Walls taller than 4 feet almost always need tieback geogrid reinforcement, deadmen anchors, or a reinforced concrete core. DIY is feasible up to 3 feet; beyond that, hire a licensed mason or landscaper with engineering sign-off.
Brick Types That Work
Solid clay pavers or SW-grade (severe weather) bricks resist freeze-thaw and handle ground contact. Expect to pay $0.75 to $2.50 per brick. Avoid hollow brick, which fills with water and cracks within 3 to 5 winters in any climate below 20°F.
Engineered concrete retaining-wall blocks like Versa-Lok or Allan Block cost $4 to $8 per block and install faster than true bricks because they lock with rear flanges. These are technically concrete masonry units but are often called brick walls colloquially.
Footing Requirements
Every brick retaining wall sits on a compacted gravel base 6 inches thick and 24 to 30 inches wide, extending below the frost line for your region. In zones 5 to 6, frost depth is 36 to 48 inches; in the Deep South, 12 to 18 inches suffices.
For walls over 3 feet, replace gravel with a reinforced concrete footing 8 inches thick, 24 inches wide, containing two courses of #4 rebar tied into vertical dowels every 16 inches. Let the footing cure 3 to 5 days before laying brick.
Drainage Is Non-Negotiable
Water pressure behind retaining walls generates enough force to push them over. Install a 4-inch perforated drain pipe (French drain) along the base of the back side, sloped at 1/8 inch per foot toward a daylight outlet or sump.
Backfill the wall with 3/4-inch clean gravel for at least 12 inches behind the wall, extending up to within 6 inches of finished grade. Separate gravel from native soil with landscape fabric to prevent silt from clogging the stone matrix.
Mortar and Joint Techniques
Use Type S mortar (1,800 psi compressive strength) for retaining walls rather than the weaker Type N used in interior veneer. Mix to a stiff consistency that holds a peak when scooped.
Lay bricks with 3/8-inch joints, offsetting each course by half a brick so no vertical seam runs more than two courses. Butter each brick end before placing, and strike joints with a concave jointer after mortar thumbs firm.
Reinforcement for Taller Walls
Walls 3 to 6 feet tall need vertical rebar every 24 to 32 inches, grouted solid from footing to cap. Walls 6 feet and above require engineered design, usually with geogrid reinforcement extending 4 to 8 feet back into the hillside every second or third course.
Deadman anchors, made from pressure-treated 6×6 posts buried perpendicular to the wall, tie the structure back into stable soil. Spacing is typically every 4 to 6 feet along the wall.
Step-by-Step Build Sequence
Step one: lay out the wall with stakes and mason’s line; excavate the trench 8 inches below finish grade, 24 to 30 inches wide. Step two: compact a 6-inch gravel base or pour concrete footing; let cure. Step three: dry-lay the first brick course to confirm layout and spacing.
Step four: mortar the first course, checking level every 4 feet. Step five: build up, inserting weep holes every 6 to 8 feet in the second course. Step six: install drain pipe and backfill with gravel as you rise. Step seven: cap with a solid row of coping bricks or pre-cast concrete caps set in mortar.
Cost and Labor Estimates
DIY material cost for a 20-foot-long, 3-foot-tall brick wall runs $600 to $1,200 including gravel, drain pipe, mortar, and bricks. Add $150 for tool rentals (mixer, tamper, mason’s tools) if you do not own them.
Professional installation typically costs $30 to $55 per square face-foot for brick walls, which puts the same 20-by-3-foot wall at $1,800 to $3,300. Engineered walls over 4 feet tall run $65 to $120 per square face-foot with permits, plans, and inspections included. Budget an extra 15% contingency for any retaining wall project since hillsides rarely match initial measurements.
Common Failure Modes
Most brick retaining walls fail in three predictable ways. Tipping failure happens when water pressure pushes the wall forward without drainage; you will see horizontal cracks at the base and visible lean at the top. Bulging failure comes from frost heave or soil swell, creating a curved middle section that protrudes 1 to 3 inches. Settling failure drops sections of the wall when footings were laid on organic topsoil rather than compacted subsoil.
Inspect existing walls every spring after snowmelt. Any crack wider than 1/8 inch, any visible lean checked with a 4-foot level, or any displaced cap brick means the wall is moving. Repair catches at the tilting stage cost $300 to $1,500 in drainage retrofit; walls left to fail often require complete demolition and rebuild at full new-construction price.
Caps, Aesthetics, and Finishing Details
A proper cap both protects the wall top from water infiltration and visually finishes the structure. Pre-cast concrete caps run $8 to $18 per linear foot and come in beveled, bullnose, or flat profiles. Stone veneer caps using bluestone or limestone cost $20 to $40 per foot but look dramatically more expensive than they are.
Set caps in a full mortar bed, not dabs, with a slight backward slope (1/4 inch per foot) to shed water away from the fill side. Seal the cap course with a penetrating sealer like Prosoco Saltguard ($70 per gallon, covers 150 square feet) every 3 to 5 years to keep moisture out of the mortar joints. Plant trailing perennials like creeping thyme or sedum at the base to soften the wall visually and hide the weep holes without blocking them.
