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Home > Lowe's for Pros > Waterproof a wet basement

Waterproof a wet basement

Waterproof a wet basement

By Fiona Wagner

Finishing a basement can give a homeowner some valuable space for a recreation room, office or even a bedroom. But if the space seems damp or musty, that's a red flag for any contractor.

Before moving forward with any basement remodel, contractors must first ask the homeowner if their space is dry, says Don Fugler, senior researcher, policy and research division, Canada Mortgage and Housing Corp. "The contractor should definitely undertake an inspection before doing any work or even giving an estimate. The amount of moisture present and how it arrives should define how the contractors does the work."

The risks of skipping this evaluation are real: It creates a ticking time bomb for both the homeowner and the contractor.

"Many homeowners will try to finish a basement even though it has leaks or moisture issues," Fugler adds. "Almost inevitably—within months or years—the basement stinks and there is mold happening in the studs and along the drywall." Both scenarios can result in an unusable and unsafe space.

Detecting moisture

In some homes, water damage and mold damage aren’t apparent so contractors must rely on the small signs of a basement moisture problem: efflorescence (white, chalky stains), condensation on windows or pipes and moisture or mold-damaged finishes. When a basement is finished, locating the source of water leakage can be difficult. One of the best ways to properly assess the problem is by using an inexpensive moisture detector, that provides a meter reading of moisture levels in a wall. "Say the homeowner has a block foundation," says Jonathan McMahon, Operations Manager, DryShield Water Solutions Corp. in Toronto. "The drywall could be 100 percent dry, but the walls could be full of water that hasn't broken through yet."

Causes of a damp basement

Before a contractor can assess how to repair a wet basement, they must get to the root of the problem and figure out what’s causing the dampness in the first place. There are two main causes of a damp basement; the first is a condensation problem caused by the differential in temperature between the cold, below-grade basement walls and the warm, moist interior air. This problem is relatively easy to fix: Advise the homeowner to use a dehumidifier or insulate the basement walls. If insulated walls are used, Fugler advises contractors to use a spray foam insulation since most conventional insulations are not airtight.

The second cause, however, isn’t as easy to fix. Water that seeps in from the exterior of the house through a crack, a joist leak or through the concrete, can be the most destructive and can deteriorate basement walls, floors and foundation over time, Fugler says. While quick fixes such as spray-on sealants and crack injections may stop the leaks temporarily, water will always follow the path of least resistance, finding any void it can. McMahon adds that a more permanent fix is an external waterproofing solution or an internal draining system.

Internal versus external solutions

Once the contractor identifies the source of the leak and type of foundation, there are two solutions to fix the problem. The first and traditional way is an external solution, which involves excavating down to the side of the footing, and sealing off the walls with a waterproof product before installing a new drainage system.

"The most important thing when you waterproof is to give that water somewhere to drain to," says McMahon. That can mean connecting the weeping tiles to the existing storm or sanitary drain or a sump pump. The walls are then sealed with a waterproofing product such as rubberized urethane and a dimple board is installed on top.

The second, cheaper and less intrusive solution—when working with an unfinished basement—is internal, whereby a trench is dug along the affected wall along the inside of the footing, and new weeping tile is installed at the side of the footing and connected to a sump pump.

How to choose

Factors such as budget and features of the particular house (is the basement finished? Is there a deck along the affected wall?) will influence which approach will work best. Professionals should assess each basement, and decide on the best approach. There's no one size fits all solution: "It’s based on each situation," says McMahon.

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