Garage Leaking Water Through the Walls

by Robert Korpella

Water leaks result from a variety of problems, and tracking them to their source can be an issue in itself. Whether made from concrete or wood, the interior of garage walls often are left unfinished (unless the wall adjoins living space). Without drywall, and maybe even insulation, the task of tracing a water leak to its source is easier than in finished spaces. Water can travel some distance from the leak’s point of origin to the point where it comes through the walls, so a thorough inspection is warranted.

Cracks and Crevices

Concrete walls are naturally porous, and some develop cracks or tiny holes after they cure. Even tiny openings have the potential of allowing water to enter the garage. Walls built below grade -- such as those in a garage on a split-level or raised-ranch home -- are also subject to pressure from water in the ground. The small crevices in concrete act as capillaries that allow water to flow into the garage. Patch obvious holes with hydraulic cement, and coat the walls with waterproof masonry products that create a membrane through which water can't pass. With wood or concrete walls, seal any potential water entrances, such as where electrical wiring, cables or pipes enter the garage. Gutters and downspouts that direct water away from the garage reduce the amount of water near the walls during a rain.

Check the Roof

Water may enter the garage through the walls, but the source of the leak could be higher on the structure. Flaws in the roofing materials, or the flashing where the roof meets a wall, can let water in. The water travels along the garage’s framing studs before emerging through walls. Look for wood that is wet or discolored from acting as an avenue for water travel. This is problem is exacerbated during wet weather.

Joint Seams

Any seams where a wall -- wood or concrete -- meets a door, window or utility box are invitations for water entry. Seal these seams with caulk or waterproof foam sealants. Even if the garage’s interior walls are unfinished, finding these seams is easier to do outside the building. The sill plate -- where wood walls meet concrete walls, foundations or slabs -- are also a potential seam for water entry. Seal these with caulk or foam.

Humidity and Other Issues

While more likely to seep gently than leak, high humidity levels or condensation pose problems that could appear as leaky garage walls. If your garage has plumbing in the walls they may not be adequately insulated, which results in condensation. High humidity levels are more likely in garages with full or partial concrete walls than wood walls since concrete wicks and retains moisture more readily than wood. A patch of foil taped to a wall, then checked after several days provides a clue as to the source of moisture problems. Water on the outside of the foil indicates high humidity, while a wet surface on the concrete wall behind the foil indicates high moisture content, which may be evidence of water passing through the wall.

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