What are the common causes of failed retaining walls?

Hydrostatic pressure (water accumulating in soil behind walls) is a leading cause. Other problems include inadequate base, poor compaction, missing geogrid, and under-designed reinforcement.

What materials are used in professional retaining walls?

Common materials include CMU (cinder block), manufactured concrete blocks (Angelus or Allan Block), poured concrete, natural stone, and gabion baskets.

Retaining Wall Contractor

Martin Romero
Apr 2
9 min read

Updated: Apr 4

Los Angeles hillsides present unique challenges that demand specialized retaining wall construction. From heavy winter rains concentrated between October and April to expansive clay soils that swell and shrink with moisture, Southern California properties face conditions that can destabilize slopes and threaten foundations. Add seismic activity from the San Andreas Fault and local faults like the Hollywood Fault, and the stakes become even higher. Many properties in the area require retaining walls to stabilize slopes and protect homes from these risks.

A professional retaining wall contractor designs and builds retaining walls to prevent soil erosion, manage drainage, and create usable outdoor space on sloped lots. Retaining walls are commonly built to create greater flat surface area for practical use, such as gardens or patios, especially on hillside properties. Custom retaining walls can be designed to enhance both the functionality and aesthetics of outdoor spaces, making them ideal for challenging terrain. Quality work is essential in retaining wall construction to ensure long-term durability and safety. This guide covers when you need a contractor, what the build process involves, and how design elements like finishes, caps, and lighting transform structural walls into high-end landscape features. Proper construction, waterproofing, and drainage are critical—without them, walls lean, crack, or collapse.

Retaining walls can increase property value by expanding usable outdoor space and improving landscape design.

Retaining walls can protect homes from water intrusion and soil erosion during heavy rains.

Water from rain will always run down a slope, and retaining walls help hold back water, dirt, and debris from damaging properties.

Do You Need a Retaining Wall Contractor?

Common signs indicate you need a retaining wall or must replace an existing one: sliding soil on slopes, pooling water near foundations, tilting walls exceeding 1 inch over 10 feet, or sinkholes forming in your yard from subsurface erosion.

Typical Los Angeles scenarios requiring professional intervention include:

Hillside homes positioned above or below neighbors in areas like Griffith Park or Hollywood Hills
Properties adjacent to canyons prone to debris flows during El Niño events
Homes affected by heavy storms between October 15 and April 15
Lots with severe grade changes supporting driveways, patios, or structures

Walls over 3–4 feet in height require a professional wall contractor and often an engineered plan plus permit from LADBS. DIY approaches suit only very small garden edging under 2 feet—not structural retaining walls where amateur builds fail 70% within five years.

Types of Retaining Walls a Contractor Can Build

Different retaining wall systems are commonly designed for various purposes, such as supporting landscape features, controlling erosion, and creating flat surfaces. These systems serve specific purposes based on wall height, soil conditions, site access, and desired appearance. Understanding your options helps you make informed decisions about your hillside property.

Gravity retaining walls rely on sheer mass to resist soil pressure. These thick structures use large concrete blocks, boulders, or gabion baskets filled with rock, working well for moderate heights where weight alone provides stability. Gabion walls are composed of decorative rocks held together by metal wires and are designed to control water flow without damaging the soil.

CMU structural retaining walls—often called concrete block retaining walls—feature hollow-core masonry units reinforced with rebar and solid grout fill. These engineered solutions handle hillside stabilization and support significant loads.

Segmental block systems like Angelus Block or Allan Block use interlocking blocks and interlocking geometry for tiered landscaping and garden terraces. These manufactured blocks create landscape retaining walls without traditional mortar.

Wood retaining wall options are also available, suitable for gardens, slopes, or decorative purposes, providing both functional and aesthetic solutions.

Poured-in-place concrete and shotcrete walls address tight access, tall heights, or custom curves following property lines.

Retaining walls in Los Angeles are built to meet varying grading requirements, and most retaining wall contractors in Los Angeles provide services for hillside terrain, including design and engineering tailored to soil type and slope. Local expertise ensures that walls in Los Angeles comply with all relevant regulations and are suited to the unique challenges of the area.

Poured-in-Place Concrete and Shotcrete Walls

Poured-in-place walls use wood or steel forms filled with concrete, while shotcrete is pneumatically sprayed onto rebar cages. Both options excel for taller walls on steep slopes, limited construction space behind existing homes, or custom profiles.

Structural rebar cages, engineered footings, and inspections are typically required. Exposed faces can remain smooth, receive broom finishing, or be prepared for stucco and stone veneer.

CMU Block Retaining Walls

Hollow-core concrete masonry units stack on reinforced concrete footings, with vertical and horizontal rebar creating a structural grid. Cells containing rebar are filled with concrete grout, creating a monolithic structure for walls over 3–4 feet.

CMU walls commonly appear behind homes, along property lines, and for basement retaining structures. Contractors apply stucco or veneer to match home exteriors and other hardscape features.

Segmental Block and Garden Walls

Interlocking systems like Angelus Block and Allan Block set on compacted base without mortar, locking together with pins or lips. When designed with geogrid reinforcement, these walls handle terraced yards and medium-height applications.

Masonry blocks come in multiple colors and textures with integrated corners and capstones. Garden walls under 2 feet may not require engineering but still benefit from proper compaction and drainage.

Materials Used in Professional Retaining Walls

Selecting the right material impacts cost, overall appearance, and long-term performance—especially critical given heavy rains and seismic activity in Los Angeles. A strong foundation is essential for retaining wall stability and safety, ensuring the structure meets local codes and withstands environmental stresses. Some retaining wall contractors also specialize in foundation repair, providing expertise in both new construction and reinforcing existing foundations for structural integrity.

CMU (cinder block): Versatile, engineer-friendly material excellent for structural walls receiving stucco or veneer
Manufactured concrete blocks: Pre-engineered units with consistent quality for interlocking segmental systems
Poured concrete: Strong, monolithic option for complex shapes finished with decorative coatings
Natural stone: Premium choice for high-end landscapes with timeless aesthetics and higher labor costs
Gabion baskets: Wire cages filled with rock for drainage-heavy conditions and creek banks

The cost to build a retaining wall depends on several factors, including the wall's purpose, height, length, and materials used. Financing options for retaining wall construction may also be available through contractors.

Pros and Cons of Common Retaining Wall Materials

CMU offers high strength and code compliance, making it ideal for properly reinforced structural applications. However, unfinished CMU appears plain without stucco or veneer.

Segmental blocks provide fast wall installation and attractive textures, though very tall walls require geogrid reinforcement. Multiple color options create aesthetically pleasing results.

Poured concrete delivers structural capacity and design flexibility but demands careful forming and curing to prevent cracking.

Natural stone presents upscale durability balanced against higher costs and skilled mason requirements.

How a Contractor Properly Builds a CMU Retaining Wall

Professional CMU retaining wall construction on Los Angeles hillsides follows established procedures ensuring structural integrity and longevity.

Site evaluation: Review plans, property lines, elevations, and soil reports; mark wall alignment with stakes
Excavation: Dig trenches 18–30 inches deep per engineer specifications
Footing: Pour reinforced concrete with horizontal rebar and vertical L-bars extending into CMU cells
Block installation: Level first course on cured footing, stagger successive courses with rebar grid
Grouting: Fill cells with concrete in lifts, locking rebar and blocks into solid structure
Inspections: California requires footing, rebar, and grout inspections before proceeding

Waterproofing CMU Retaining Walls

Any wall holding back soil near living spaces requires waterproofing on the soil side. Contractors apply bituminous tar coating or high-performance membranes before backfilling.

Protection boards or foam panels shield waterproofing from gravel damage during compaction. Some projects add rigid foam where retaining walls form part of habitable space.

Drainage Behind the Wall: Gravel and SDR-35 Pipe

Place 12–18 inches of 3/4” crushed rock directly behind the wall, allowing water to flow to a perforated SDR-35 drain pipe at the base. This heavy-duty PVC pipe slopes approximately 1% to daylight or an approved drainage system.

Filter fabric wraps gravel and pipe to prevent fine soils from clogging the system. Weep holes at intervals release built-up water, reducing hydrostatic pressure that causes 60% of failures.

Segmental Block Retaining Walls: Angelus and Allan Block Systems

Segmental retaining walls rely on block geometry, mass, and geogrid reinforcement rather than continuous concrete and rebar. The build process includes:

Excavate below grade and place compacted Class II road base (6–12 inches)
Install leveling pad for dead-level first course
Stack courses with proper setbacks and clean surfaces for tight interlock
Place manufacturer-approved geogrid at engineered heights, extending into retained soil
Install drainage stone and perforated pipe similar to CMU systems

When to Use Segmental Block vs CMU or Poured Concrete

Segmental block suits landscape terraces, curves, and visible walls where aesthetics matter. CMU or poured concrete handles very tall walls, tight property lines, or walls directly supporting structures and driveways.

An experienced retaining wall contractor evaluates soil reports, wall height, and site conditions to recommend the appropriate system for your project.

Critical Drainage Design: Preventing Hydrostatic Pressure

Hydrostatic pressure—water accumulating in soil behind walls—ranks among leading causes of failed retaining walls. Proper drainage design prevents this destructive force.

Key drainage components include:

Free-draining gravel zone directly behind the wall
Sloped backfill directing water downward
Filter fabric protecting stone from soil migration
SDR-35 perforated pipe at the base with proper slope
Surface drains above walls diverting runoff away from backfill

In hillside neighborhoods, contractors integrate French drains or stormwater systems keeping water away from foundations and neighboring properties.

Finishes and Aesthetic Options for Retaining Walls

A retaining wall serves dual purposes as both structural element and design feature when finished properly. Contractors match wall finishes to home exteriors, existing hardscapes, or neighborhood styles common throughout Los Angeles.

Smooth & Stucco Retaining Wall Finishes

Stucco applied over CMU or concrete walls creates a uniform, clean look after proper surface preparation. Popular textures include smooth trowel and sand finish in colors matching the house.

Waterproofing behind stucco prevents bubbling and efflorescence. Expect repainting every 8–15 years depending on exposure.

Veneer Finishes: Stone, Brick, and Concrete Veneer

Stone veneer—natural or manufactured—adds depth and texture ideal for front yard walls and outdoor living areas. Brick veneer ties into existing home details like chimneys and traditional facades.

Installation requires proper lath, mortar, and weep screeds at the base for moisture management.

Split-Face and Decorative Block Walls

Split-face CMU blocks feature factory-created rough textures eliminating additional veneer needs. Decorative blocks in multiple colors reduce long-term maintenance compared to painted finishes.

Natural Stone Facing and Custom Masonry

Full-depth stone facing represents a premium option for estates and custom outdoor spaces. Styles like dry-stacked and random ashlar each offer distinct character, though installation requires skilled masons.

Wall Caps: Protecting and Finishing the Top of the Wall

Caps provide both aesthetic purposes and functional protection, shedding water away from wall cores and preventing moisture infiltration. Options include precast concrete, natural stone slabs, matching modular caps, or poured-in-place concrete.

Contractors design caps with slight overhangs and drip edges directing rainwater away from wall faces. Proper installation with mortar or high-strength adhesive improves longevity.

Types of Retaining Wall Caps

Precast concrete: Standardized sizes coordinating with segmental systems
Natural stone: Bluestone, limestone, or granite for high-end applications
Matching system caps: Angelus Block or Allan Block products for perfect coordination
Poured-in-place: Custom shapes integrated with stair treads

Integrating Lighting into Retaining Walls

Lighting transforms retaining walls into nighttime design features while improving safety on paths and driveways. Planning for electrical lines must happen during construction before backfilling.

All exterior lighting should be wet-location rated, typically using low-voltage LED systems for efficiency.

Under-Cap and Hidden Strip Lighting

LED strip fixtures mounted beneath wall caps wash light down the face, creating ambient glow for modern patios and outdoor entertaining. Wiring conceals within walls, routed to accessible transformers.

Step, Face, and Accent Lighting

Recessed step lights illuminate stairs and pathways for nighttime safety. Wall-mounted accent fixtures highlight stone textures, while in-ground uplights create depth in the landscape.

Waterproofing and Long-Term Performance

Well-built retaining walls last decades when moisture and drainage are controlled from construction. Contractors combine waterproof coatings, drainage systems, proper compaction, and expansion joints to minimize cracking.

Direct irrigation away from wall faces and avoid over-watering planters above walls. Periodic maintenance includes checking outlets, monitoring for cracks, and clearing drainage channels.

Common Retaining Wall Problems When Work Isn’t Done Right

Many repair calls involve walls constructed without proper footings, reinforcement, or drainage:

Leaning/bowing: Inadequate base, poor compaction, missing geogrid
Cracking: Settlement, thermal movement, under-designed reinforcement
Bulging/blowouts: Water pressure from blocked drainage
Aesthetic issues: Efflorescence, staining, spalling from moisture intrusion

Replacing failed retaining walls costs far more than building correctly initially—property owners often face $50,000–$500,000 in repairs.

When to Hire a Professional Retaining Wall Contractor

Any structural wall or wall over 3–4 feet high requires a licensed retaining wall contractor. Factors triggering professional involvement include:

Hillside construction conditions
Proximity to buildings or property lines
Supporting driveways, pools, or structures
Areas prone to heavy runoff

California requires engineer designs, retaining wall permits, inspections, and sometimes geotechnical reports for larger walls. Contractors coordinate surveying, permitting, and approvals while ensuring hillside codes compliance.