Small, non-structural landscaping walls (under 4 feet, not supporting structures or critical slopes) may be feasible for experienced DIYers. Walls over 4 feet in height, those supporting structures, critical slopes, or requiring engineering plans, must be designed and often constructed by licensed professionals due to significant safety and structural implications.
Retaining wall construction involves critical considerations for soil mechanics, drainage, frost protection, and structural integrity, especially for walls exceeding 4 feet in height or supporting significant loads. Proper design and adherence to local codes are essential to prevent failure and ensure long-term stability in DuPage County's climate and soil conditions.
Project Guidelines & Rules
General Requirements & Permits
5 Rules
Permit Application
Contact your local building department for specific permit application forms, required documentation (e.g., site plans, engineering drawings), and fee schedules.
When a Permit is Required
Generally, retaining walls exceeding 4 feet in height, measured from the bottom of the footing to the top of the wall, or walls supporting a surcharge or impounding flammable liquids, require a building permit. Your local building department may have stricter requirements.
Engineering Review
Retaining walls exceeding 4 feet in height, or walls subject to special design conditions (e.g., steep slopes, specific soil conditions, supporting structures, or adjacent to property lines), shall be designed and sealed by a licensed Illinois professional engineer. (Based on IRC R404.1.3 exemption for 4ft walls)
Site Plan Requirements
Submitted plans shall include a detailed site plan showing property lines, existing structures, proposed wall location, dimensions, elevations, drainage, and utility locations. (General Code Requirement)
Setbacks
Verify specific setback requirements from property lines, other structures, and utility easements with your local municipality. (General Code Requirement)
Design & Structural Integrity (2024 IRC)
6 Rules
Frost Protection
All footings for retaining walls shall extend a minimum of 42 inches below finished grade to protect against frost heave, aligning with DuPage County's frost depth requirements. (DuPage County Climate Standard based on IRC R403.1.4.1)
Wall Height and Design
Retaining walls exceeding 4 feet in height measured from the bottom of the footing to the top of the wall shall be designed in accordance with accepted engineering practice. (IRC R404.1.3)
Lateral Earth Pressure
Walls shall be designed to resist the lateral pressure of retained earth, including any surcharge loads, hydrostatic pressure, and seismic forces. (IRC R404.1.3.1)
Foundation Design
Foundations shall be designed to prevent overturning, sliding, and excessive settlement. Bearing soil conditions shall be verified. (IRC R403.1, R404.1.3.2)
Wall Materials
Materials used for retaining walls, such as concrete, masonry, or treated timber, shall be suitable for their intended use and conform to applicable material standards. (IRC Chapter 4, ACI 318, TMS 402/602 where applicable)
Reinforcement
Concrete and masonry walls shall be reinforced as required by engineering design to resist bending moments and shear forces. (IRC R404.1.3.3)
Drainage & Soil Stability (2024 IRC)
4 Rules
Backfill Drainage
A drainage system shall be provided behind all retaining walls to prevent the accumulation of hydrostatic pressure. This typically includes a layer of granular backfill (free-draining material) extending behind the wall and a perforated pipe. (IRC R405.1, R404.1.3.1)
Perforated Drain Pipe
A minimum 4-inch diameter perforated pipe, designed for subsurface drainage, shall be installed at the base of the wall's granular backfill and sloped to daylight or to an approved storm drainage system. (IRC R405.1)
Filter Fabric
Geotextile filter fabric shall be placed between the granular backfill and the native soil to prevent soil migration into the drainage system. (Good Engineering Practice)
Surface Water Diversion
Surface water shall be diverted away from the top of the retaining wall to prevent erosion and saturation of the backfill soil. (IRC R401.3)
Electrical Considerations (2023 NEC)
4 Rules
Protection of Wiring
All wiring installed in, on, or adjacent to retaining walls shall be protected from physical damage. Where subject to physical damage, conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 PVC conduit, or other approved methods. (NEC 300.5, 300.6)
Underground Installations
Underground conductors and cables shall be installed with minimum cover requirements based on their voltage, location, and protection method. Verify specific requirements with your local municipality for any excavation near existing utilities. (NEC 300.5)
Outdoor Outlets and Luminaires
Outdoor receptacles shall be weather-resistant (WR) type, GFCI protected, and provided with appropriate enclosures (e.g., 'in-use' covers where applicable). Outdoor luminaires shall be rated for wet or damp locations. (NEC 210.8(A)(3), 406.9, 410.10(A))
Grounding and Bonding
All non-current-carrying metal parts of electrical equipment, enclosures, and raceways shall be properly grounded and bonded. (NEC Article 250)
Plumbing Considerations (Illinois Plumbing Code)
3 Rules
Protection of Existing Plumbing
Excavation for retaining walls shall not undermine or damage existing water, sewer, or storm drainage lines. Any existing lines encountered must be protected or relocated in accordance with the Illinois Plumbing Code. (Illinois Plumbing Code Section 890.130)
Drainage Connections
If retaining wall drainage systems (e.g., perforated pipe outlets) connect to an approved storm drainage system, such connections shall comply with the Illinois Plumbing Code and local storm sewer ordinances. (Illinois Plumbing Code Section 890.1510)
Backfill Around Piping
Backfill material around underground plumbing piping shall be free of rocks, broken concrete, or other deleterious materials and compacted in layers to prevent damage to the pipes. (Illinois Plumbing Code Section 890.130)
Inspections
3 Rules
Footing/Foundation Inspection
An inspection of the excavation, reinforcing steel, and drainage components shall be conducted prior to the placement of concrete or backfill. Coordinate with your local building department for scheduling.
Drain Tile/Backfill Inspection
An inspection of the drainage system, granular backfill, and filter fabric may be required prior to final backfill. Coordinate with your local building department for specific requirements.
Final Inspection
Upon completion of the retaining wall construction, a final inspection shall be conducted to ensure compliance with approved plans and all applicable codes. Coordinate with your local building department for scheduling.
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