Basement Waterproofing near you

Most wet basements have one main source, sometimes two. Telling them apart matters, because each one calls for a different repair and a different trade.

Natural Resources Canada lists the usual symptoms of dampness on foundations and basement finishes as staining or mould growth, blistering and peeling paint, efflorescence and spalling, along with a musty smell. Many of them appear long before any water reaches the floor.

A contractor who proposes a system before finding out where the water gets in is guessing. A proper diagnosis starts with when the water appears, whether after heavy rain, during the spring thaw, on humid July days or all year long, and where it appears: at a single crack, along the joint between the floor and the wall, under a window or near a pipe.

Natural Resources Canada suggests a simple test to separate condensation from moisture coming through the concrete: tape a sheet of plastic about 1 m (40 in.) square to the wall or the slab and look at it after a day or two. Moisture on the room side points to humid indoor air, while moisture underneath means it is moving in from the ground.

Exterior waterproofing stops water at the outside face of the foundation. The soil is dug out down to the footing, the wall is cleaned and repaired, a membrane is applied and the drain at the base of the footing is renewed before the trench is backfilled. It keeps the concrete itself dry, and it's the route Natural Resources Canada points to for serious water problems, while minor leaks can sometimes be solved by directing water away from the house.

Interior waterproofing manages water once it has reached the foundation instead of keeping it out of the wall. The contractor cuts a channel in the slab along the walls, lays a perforated drain beside the footing and connects it to a sump pit, then fits a dimpled membrane on the walls to guide seepage down into the drain. Paint-on sealers and coatings are a different thing altogether: at best they help with light dampness, and they don't hold back water under pressure.

Many houses end up with a mix of both: exterior work on the wall that takes the most water, where digging is possible, and an interior drain along walls hemmed in by a driveway, a deck, a garage or the house next door.

Each option solves a different problem, so the comparison only makes sense once the source of the water is known.

A damp basement and mould go hand in hand. Health Canada warns that mould can start growing within 48 hours wherever there is excess moisture, and that people living with mould and dampness are more likely to suffer eye, nose and throat irritation, coughing, wheezing and worsening asthma. Its first rule is to fix the water problem that caused the mould, including repairs to the foundation when water is getting in from outside, or the mould will come back.