How To: Deal With Water in Basement Walls

Q I just bought my first home, an end-unit townhome with a walk-out basement. Only the rear, walk-out side is finished. During the home inspection, the inspector noted that the walls of the unfinished front half were painted with waterproofing paint, and though they looked to be in good condition, there was definitely water on the outer side.

After each rain, more water is visible as dark splotches beneath the paint, though none is leaking through. Several waterproofing companies have recommended installing a sump pump. Is this the right way to address the issue? How urgent is the repair? I would like to completely finish the basement at some point. If a sump pump is the best solution, what should I keep in mind when choosing a company?

Crofton

A If you were seeing water stains high up on the basement walls, you'd probably have a surface water issue, such as an overflowing gutter or a downspout emptying too close to the house. But when water seeps in low on the walls, the water is generally moving underground. The solution is a drainage system that intercepts the water and delivers it downhill from your house.

You might be able to do this outside by installing a curtain drain, also known as a French drain. Basically, you (or a landscaper) dig a narrow ditch across your yard on the uphill side and along the sides downhill far enough so that water in the ditch can empty to where it won't cause a problem. You fill the ditch with four-inch perforated pipe plus round gravel about 1 1/2 inches in diameter. Water always flows through the path of least resistance, so the pipe and spaces between the stones work like a highway, ushering the water away from your house.

However, if you have a lot of expensive landscaping in the way, digging up your yard might be a lot of hassle. In that case, you can accomplish the same thing inside by having a basement waterproofing company cut through your basement floor along the walls, dig a shallow trench, install perforated pipe and then cover most of the opening with cement. The crew needs to leave a small gap between the wall and floor, though, so that if leaks develop higher up, the water can dribble down into the pipe. You'll need a sump pump to get the water that's collected out into a storm drain or a safe exit on your property. To ensure that the pump operates even if a storm kicks out power, be sure to get battery backup, preferably with a system that recharges automatically when the power is on.

As to selecting the best company, do the standard things: Get several bids. Make sure your preferred company is licensed and bonded. Phone a couple of past customers and ask for their advice. Some companies have separate sales and construction crews, so don't necessarily go by which person you like best. Because you hope to finish this space, factor in the way the company will detail the gap left next to the walls.

Because water is not getting into your basement, fixing the problem isn't a must-do task for today. But ensuring a dry basement should rank higher in priority than cosmetic home-improvement changes. A wet basement can lead to many expensive repairs down the road, including things you might never think of, such as the need to get a new roof.

When moisture collects under a house, it can move up through the structure and condense on the back of the roof, causing the sheathing to rot and the roof to fail prematurely. Addressing the moisture issue soon will let you see whether the system works before you cover everything with finished surfaces.

Jeanne Huber

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