Do I need drainage installed under my patio in New Brunswick?

In most cases, yes — New Brunswick patios benefit significantly from dedicated drainage, especially if the patio is adjacent to a house foundation, sits on clay-heavy soil, or is in a low-lying area. NB receives 1,100–1,200mm of annual precipitation plus substantial spring snowmelt, and all that water needs somewhere to go. A patio without drainage can trap water beneath it, leading to frost heave, foundation damage, and premature failure.

The patio surface itself provides primary drainage through its slope and permeable joints. Every NB patio should slope at a minimum of 1/8 inch per foot (1% grade) away from any structures. This directs surface water off the patio rather than letting it pool. Polymeric sand in paver joints allows some water to percolate through slowly, and the 12–16 inch granular base beneath the pavers acts as a drainage reservoir that disperses water into the surrounding soil.

Foundation-adjacent patios need active drainage. When a patio meets a house foundation wall, water running off the patio surface can pool against the foundation and seep into the basement — a common and expensive problem in NB homes. Install a 4-inch perforated drainage pipe in a gravel-filled trench along the foundation side of the patio, wrapped in filter fabric to prevent clogging. This pipe should slope at minimum 1% grade toward a suitable outlet — either a dry well, a rain garden, or daylight at a lower point in the yard. The cost for this foundation drainage is approximately $10 to $20 per linear foot and prevents thousands of dollars in potential water damage.

Clay soil areas require enhanced drainage. If your property has the heavy clay soil common around Fredericton, the Saint John River valley, and many inland NB locations, water does not percolate through native soil efficiently. The granular base under your patio will fill with water during heavy rain or spring thaw and have nowhere to drain. In clay soil situations, install perforated drainage pipe along the lowest edge of the patio base, running to a daylight outlet or dry well. Some contractors in NB install a full drainage grid beneath the patio base for severe clay conditions.

Sandy coastal soils may not need additional drainage. Properties near Moncton, Shediac, Miramichi, and along the coast often have sandy, well-draining soil that naturally wicks water away from the patio base. If you can dig a hole, fill it with water, and it drains within 30 minutes, your soil likely provides adequate natural drainage. In these situations, the standard granular base and proper surface slope may be sufficient without dedicated drainage pipe.

Spring snowmelt is NB's biggest drainage challenge. When 250–300cm of accumulated snow melts over 2–4 weeks in March and April — often while the ground is still partially frozen — massive volumes of water need to move away from your patio and foundation. A drainage system sized for summer rain may be overwhelmed by spring thaw conditions. Ensure your drainage outlet doesn't terminate in an area that will be frozen or snow-covered during the critical March–April thaw period. Professional patio drainage design and installation in NB adds $500 to $2,000 to the overall patio project cost — a worthwhile investment given the province's challenging water management conditions.

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