Renovation & Design

Damp spot in garage persists after eaves replaced

Determining whether moisture is coming from inside or outside is first step in solving problem

Katherine Frey / Washington Post files

A wet spot on a garage floor in winter could mean it’s the lowest spot and is taking on all the ice and snow melt from your vehicles.

Question: I am a single woman with a detached 22-by-24-foot garage, standard package and construction. It is not insulated, has stucco on the exterior and is wired. It was built in 2002 and almost every year I see a wet patch on the cement floor, in the southeast corner, when winter begins to thaw or in milder weather. I have had new eavestroughs installed, as the originals did not slope properly for rain drainage. I thought that I had cured the issue, but apparently not! When we had a bit of warm weather a few weeks ago, there was moisture in the corner, like before. I am very disappointed.

I am mainly an academic and not a person who is really experienced with fixing things, but I can give it a good go, if needed. I have attached photos. Do you have any suggestions for me? I am really hoping here.

Thanks very much for your kind attention.— Diane Clare

Answer: It is quite common to see some moisture on a garage floor, particularly in the early spring or winter.

There may be some minor items that you can address to remedy the problem, but first you must identify the source of the water before any action is taken.

There are only two main locations that excessive moisture in a garage can be traced to — inside or outside.

While that may seem rather simplistic, until you figure out the answer to that question, you will not be able to find a solution. Determining whether the water or wet concrete is from an exterior or interior source may require nothing more than diligent observation.

When water is seen on the garage floor, first you should look outside of the area. It appears that the area in question may be just inside your vehicle door. Open the door and look immediately outside that area. Is there snow or standing water up against the garage walls? Is the soil depressed or sloping toward the garage at that location? Is a downspout nearby and is it properly extended away from the building for one to two metres? Are the eavestroughs leaking or dripping on that side of the garage?

If any of these questions are answered in the affirmative, remedying that situation may fix the issue. Since you have stated that the eavestroughs have been replaced recently, leakage is unlikely, but how about the downspout extensions? Have you removed them for the winter to prevent freezing?

Moisture intrusion is most commonly found almost directly where downspouts are discharging, due to the concentration of high-volume water emptying from the eavestroughs at those locations. If none of these issues are seen, it may be time to look inside the garage.

It may be too early in the year to do a simple test to determine if water is coming in through the outside of the garage. But a spray test with a garden-hose nozzle, aimed at a few locations, may answer this question conclusively.

Starting with the garage walls immediately outside of the problematic southeast corner, spraying water with moderate pressure from your hose may show a point of leakage. This test will mimic wind-driven rain, which may answer why the moisture only appears periodically. Everything should be removed from inside that area, and a second person should look with a flashlight to see if water seeps through or under the wall when tested. If negative, try the same test with the vehicle and passage doors. From your pictures, I can see a small gap under the vehicle door near the corner. If water is seen leaking through that gap, a new rubber gasket should be installed, and extended all the way to the jambs, so that water cannot leak under or around the bottom of the door.

Trying the spray test on the walk-in passage door may reveal another point of ingress, which effectively could be repaired by installing or replacing a door sweep at the bottom of the door slab. Spraying other walls outside the garage, with the interior emptied, may reveal water leaking in from another location. In that case, the corner in question may be the lowest spot in the garage, which is why moisture stains or accumulation is seen there. Follow the same inspection procedure for the leaky areas for exterior grading or drainage issues, and repair them as required.

Interior sources of moisture in a detached garage will almost always come from either vehicles or equipment and tools stored inside. It may be no coincidence that the problematic moisture is seen in spring, or when there is a winter melt, because that is when moisture from the vehicles will occur. Snow and ice attached to the underside of vehicles, mud flaps, wheels and wheel wells is a certainty in our climate.

When the weather is mild outside, but snow is still on the roads, this will be even worse. Once your icy vehicle is pulled into your garage, the heat from the vehicle and the slightly warmer garage temperature may be enough for this to melt, leaking onto the floor.

Also, slush, snow and ice accumulated on the floor slab during colder weather will melt and run to the lowest point in the garage. Determination of this second potential cause of your issue may require nothing more than re-entering the garage a short time after pulling in your vehicle, when the weather is just right.

Fixing the issue of moisture in your garage should be possible after your have determined whether the source is from exterior snow and rain or from melting ice from your vehicles. Once that is determined, improved grading and water management outside, minor door repairs or snow and slush removal should solve the dilemma.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba ( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at


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