Interior basement waterproofing (drainage system and sump pump) in Cornwall typically costs $3,000 to $10,000 for an average home depending on basement perimeter length. Exterior waterproofing (excavation down to the footing, membrane application, and drainage tile) is significantly more expensive at $10,000 to $30,000. Crack injection for minor foundation cracks is much more economical at $300 to $1,000 per crack.
Look for water stains or efflorescence (white chalky deposits) on basement walls, standing water after heavy rain, a persistently damp or musty odour, rust stains on concrete or metal, paint peeling off basement walls, and cracks in foundation walls. In Cornwall, spring thaw is a common trigger for water infiltration issues that have been developing gradually.
Interior waterproofing manages water that has already entered the foundation by routing it to a sump pump. Exterior waterproofing involves excavating around the foundation, applying a waterproof membrane to the exterior wall, installing drainage tile, and backfilling. Exterior waterproofing addresses the source of the problem but costs significantly more. Interior systems are more affordable and can be highly effective for managing ongoing infiltration.
Interior drainage system installation in an average basement takes one to three days. Exterior waterproofing requiring full excavation around the foundation can take one to two weeks depending on the perimeter length and soil conditions. Crack injection repairs can usually be completed in a single visit. The scope of work significantly affects the timeline and cost.
Interior drainage and sump pump installation typically does not require a permit in most municipalities. Exterior waterproofing that involves significant excavation near a foundation may require a permit or at minimum notification to the building department. Structural crack repairs or underpinning work always require permits. Your waterproofing contractor should confirm requirements before work begins.
