Retaining Walls

• Steep site terracing: Create level building pads, yards, or driveways on sloped properties
• Cut slopes & roadway support: Hold back soil on driveway cuts or road embankments
• Erosion & slope stabilization: Prevent soil sloughing and protect structures from hillside movement
• Property line & grade changes: Retain soil at property boundaries or between different finish grades
• Landscaping & tiered gardens: Create multi-level planters, garden beds, or outdoor living spaces
• Failed or damaged walls: Rebuild walls that have tilted, cracked, or collapsed due to poor drainage or backfill
• Basement or foundation walls: Excavate for full-height foundation walls with proper drainage and waterproofing access

Site evaluation and engineering begin every wall project. We assess soil type, slope angle, surcharge loads (buildings, driveways, equipment), and drainage conditions. Walls under 4 feet on competent soil typically don't require engineering. Taller walls, poor soils, or heavy loads require structural design by a licensed engineer. We coordinate with engineers early to establish footing width, depth, reinforcement (geogrid or tiebacks), and drainage requirements before excavation begins.

Footing excavation and preparation: Retaining wall footings must bear on undisturbed, competent soil—never on fill, organics, or frozen ground. We excavate trenches to design width (typically 2-3 times wall thickness) and depth (minimum 12 inches below grade, deeper below frost). Trench bottoms are leveled, proof-rolled, and inspected before footing materials are placed. For segmental block walls, we place a compacted gravel leveling pad. For poured concrete walls, we form and pour footings per engineering plans with rebar as specified.

Drainage system installation is non-negotiable. Hydrostatic pressure from water-saturated backfill is the #1 cause of retaining wall failure. We install perforated drain pipe (4-inch minimum) at the base of the wall, wrapped in filter fabric and surrounded by clean drain rock. The pipe slopes 1-2% and daylights to a safe discharge point—never into septic fields or stormwater systems without permits. For segmental block walls, we include weep holes every 4-8 feet or use built-in drainage cores. Geotextile filter fabric separates backfill soil from drain rock to prevent clogging.

Backfill placement and compaction: Structural backfill (crushed rock or free-draining gravel) is placed behind the wall in 8-12 inch lifts and compacted with plate tampers or hand rollers. We don't use clays or silty soils—they trap water and create pressure. For walls with geogrid reinforcement, grid layers are placed at specified intervals (typically every 2-4 feet of wall height), extended back into the retained soil, and covered with compacted backfill. Each lift is compacted to 90-95% density before the next lift is placed. Compaction prevents settlement that would tilt or crack the wall.

Final grading and erosion control: Once backfill is complete, we grade the area behind the wall to direct surface water away from the wall—never toward it. Swales or berms catch uphill runoff and divert it around the wall. The face of the wall is cleaned, and any disturbed areas are seeded or mulched to prevent erosion.

• Excavators (mini to mid-size): Precise footing excavation, backfill placement, and material handling
• Loaders & skid steers: Backfill delivery, spreading, and stockpile management
• Plate compactors & jumping jacks: Lift-by-lift compaction in confined backfill zones
• Laser levels & transit: Footing elevation control and wall alignment verification
• Rock trucks & dump trailers: Haul structural backfill, drain rock, and base materials
• Structural backfill: Clean crushed rock or 3/4-minus gravel with good drainage characteristics
• Drain rock: 1-3 inch clean crushed rock for drainage zone behind wall
• Perforated drain pipe: 4-inch or 6-inch HDPE perforated pipe for back-drains
• Geotextile filter fabric: Non-woven fabric prevents soil migration into drain rock
• Geogrid reinforcement: High-strength polymer grid for mechanically stabilized earth (MSE) walls

• Wall tilting or overturning: Inadequate footing depth or width, or poor bearing soil, causes walls to lean or fall
• Hydrostatic failure: No drainage system or clogged drains create water pressure that pushes walls over
• Backfill settlement: Poor compaction causes soil to settle behind the wall, cracking pavement or structures above
• Footing failure: Shallow footings above frost depth heave and crack; footings on fill or organics settle
• Erosion and undermining: Surface water behind walls without proper grading erodes backfill and undermines footings
• Structural overload: Walls not engineered for surcharge loads (driveways, buildings) fail under applied pressure

Retaining walls in the Spokane, Newport, Coeur d'Alene, and Sandpoint region face challenging conditions. Frost heave is common—footings must extend 36-48 inches below grade (below frost depth) to prevent seasonal movement. Expansive clays in low-lying Spokane and Kootenai County sites swell when wet and shrink when dry, exerting pressure on walls—we use free-draining backfill and robust drainage systems. Rocky soils in mountain areas provide excellent bearing but are difficult to excavate—rock hammers or blasting may be required for deep footings. Steep slopes require tiered wall systems or terracing rather than single tall walls—engineering and geotechnical analysis determine feasibility. High groundwater in Bonner and Pend Oreille counties requires curtain drains uphill of walls or continuous back-drains with multiple daylight points. Seismic considerations: North Idaho is in a moderate seismic zone—walls over 6 feet or supporting structures require seismic design per IBC standards.

• Excavated footing trench to specified width, depth, and level bearing surface
• Proof-rolled and inspected footing base on undisturbed, competent soil
• Compacted gravel leveling pad or poured concrete footing per engineering plans
• Back-drain system with perforated pipe, clean drain rock, and filter fabric installed and daylighted
• Structural backfill placed in 8-12 inch lifts and compacted to 90-95% density
• Geogrid reinforcement installed at specified intervals for MSE walls (if required)
• Final grading behind wall to direct surface water away from retained soil
• As-built documentation showing footing depth, backfill lifts, drainage system, and compaction results (if tested)

A steep hillside property near Coeur d'Alene required a driveway cut with 12 feet of retained height. A single 12-foot wall would have been expensive and required deep engineering. Instead, we designed a tiered system: two 6-foot segmental block walls separated by a 10-foot bench. The lower wall footing was excavated 42 inches below driveway grade (below frost) and 24 inches wide. A 6-inch gravel leveling pad was placed and compacted. The segmental block installer built the wall with geogrid reinforcement extending 6 feet into the backfill at every other block course. We placed structural backfill (3/4-minus crushed rock) in 10-inch lifts, compacting each layer before adding the next. A 4-inch perforated drain pipe wrapped in fabric was installed at the base of each wall, surrounded by 18 inches of drain rock, and daylighted 50 feet downslope. After two winters of freeze-thaw and heavy snowmelt, both walls remain plumb with no cracking, tilting, or settlement—proof that proper excavation, drainage, and backfill are the foundation of long-lasting retaining walls.