Yes, a retaining wall absolutely needs drainage behind it to prevent water pressure buildup that can cause the wall to lean, crack, or collapse. Drainage is the single most important factor in retaining wall longevity, and it is the detail most often missed in DIY or poorly planned installations. Without proper drainage, water saturates the soil behind the wall, creating hydrostatic pressure that pushes against the structure with enormous force. In Northern Ontario, this problem is compounded by freeze-thaw cycles — water trapped behind the wall freezes, expands, and can push even well-built walls out of alignment over a single winter. Martin Services installs proper drainage systems behind every retaining wall we build across Powassan, North Bay, and surrounding areas.
How Retaining Wall Drainage Works
A properly drained retaining wall starts with a layer of clean crushed gravel behind the wall, typically 12 inches wide, running the full height of the wall from the base to within a few inches of the top. At the base of the gravel layer, a perforated drain pipe collects water as it filters down and directs it to a safe discharge point away from the wall and the property foundation. The gravel acts as a filter, allowing water to pass through freely while keeping soil particles from clogging the drain pipe. On top of the gravel, a layer of filter fabric separates the drainage aggregate from the backfill soil, preventing fine particles from migrating into the gravel over time. This system ensures that water never builds up behind the wall, eliminating the hydrostatic pressure that destroys retaining walls.
Northern Ontario Drainage Considerations
The Powassan and North Bay area presents specific drainage challenges that make proper installation even more critical. Our clay-heavy soils hold water rather than allowing it to drain naturally, which means water pressure behind retaining walls builds up faster than it would in sandier soils. Spring snowmelt and heavy summer rainstorms can saturate the ground quickly, and without drainage, a retaining wall can experience its maximum stress load within hours of a major rainfall. With 35 years of experience building retaining walls in Northern Ontario, Martin Services designs drainage systems that account for local soil conditions, slope, and expected water volume. We also ensure that drain pipes discharge to appropriate locations where the water will not cause erosion or redirect toward foundations or neighbouring properties.
Planning a retaining wall project? Call Martin Services at (249) 506-9211 for a free estimate on retaining wall installation with proper drainage. We can quote most jobs right over the phone — no waiting for a site visit.