What is the best way to waterproof a retaining wall in NB?

The most effective waterproofing system for a New Brunswick retaining wall combines a waterproofing membrane on the retained soil face, a drainage composite or crushed stone drainage layer, and a perforated weeping tile at footing level. No single product alone provides complete protection — it is the system that works, and every component matters in NB's wet climate.

The principle is simple: keep water from saturating the soil directly against the wall (drainage), prevent any water that does reach the wall from penetrating the concrete (membrane), and give the water a path to escape (weeping tile). In NB's spring thaw conditions — when multiple feet of frozen ground releases its water in a few weeks — this system is what prevents the hydrostatic pressure buildup that topples walls and saturates basements.

Waterproofing membrane options:

The best choice for poured concrete retaining walls in NB is a polymer-modified bitumen membrane applied to the soil-facing surface after the concrete has cured. Products like Bakor or Tremco systems are brush or trowel-applied and create a flexible, seamless waterproof layer that tolerates the minor movement NB's freeze-thaw cycles impose on retaining structures. Cost runs $2-$4 per square foot for material and application.

Crystalline waterproofing additives (Xypex, Kryton) can be mixed into the concrete at placement or applied as a surface treatment to cured concrete. These products form crystals within the concrete matrix that block water movement. They are excellent for new poured walls and complement but do not replace external drainage measures.

Drainage board composites — dimple mat products like Platon or Delta-MS — are often applied over the membrane before backfilling. The dimpled surface holds the membrane away from the soil, provides a drainage path for water to move down to the weeping tile, and protects the membrane from damage during backfilling. This is a best practice for NB retaining walls.

Weeping tile at footing level is non-negotiable. A 4-inch perforated pipe wrapped in filter fabric, placed at the base of the footing and sloped to drain to daylight or a sump, removes the water that collects at the base before it can build into hydrostatic pressure. In coastal NB communities near Saint John or Shediac where water tables are higher, this pipe may need to drain into a properly designed outlet rather than simply to daylight.

Backfill material matters as much as the membrane. The 12-18 inches of material immediately against the back of the wall must be clean crushed stone (3/4 inch clear), not native clay or topsoil. Native soil — especially the clay-heavy soils common around Fredericton and the Saint John River valley — traps water and negates your drainage system.

Get matched with a retaining wall or concrete waterproofing professional through New Brunswick Concrete for a proper site assessment and accurate project quote.