Moisture Source Identification in Janesville, WI

The Only Question That Matters

Every mold problem is a water problem wearing a different name. Remove the growth without answering where the water came from and you have scheduled a repeat, usually within one seasonal cycle. This page is about the diagnostic work that answers it.

In a cold climate the answer is frequently not a leak at all, which is why it gets missed. Four of the six common sources in Rock County housing involve no plumbing failure and no hole in the building.

Six Sources, and How to Tell Them Apart

How the Diagnosis Is Done

1. Take the historyAge of building, when it started, seasonal pattern, any water event and its date, what has been changed recently. Recent work is a frequent culprit — a re-roof, new windows, added insulation, a finished basement.
2. Measure the airTemperature and relative humidity inside and out, and the dew point calculated from them. In summer, a surface below the indoor dew point will condense whatever else is true.
3. Survey with thermal imagingTemperature anomalies across walls, ceilings and floors. This finds candidate areas quickly without opening anything.
4. Confirm with a meterEvery thermal finding is confirmed with a pinless sweep and then a pin reading at depth. A thermal image on its own is not evidence of moisture.
5. Map the extentWorking outward from the wettest reading until readings match an unaffected reference area. This boundary is what a scope of work is drawn around.
6. Test the hypothesisA hose test on suspect grading, isolating a supply line, or simply returning after the next rain. A source that has not been demonstrated is still a guess.

Tests You Can Run Yourself Before Calling

Three of these cost nothing and between them they separate most of the six mechanisms. Doing them before the phone call makes the conversation considerably more useful.

1. The plastic square test — separates condensation from intrusionTape a foot square of clear polyethylene tightly to the suspect wall on all four edges. Leave it 48 hours. Moisture on the room side of the plastic means water is condensing out of the air. Moisture on the wall side means water is coming through the masonry. This single test decides between a dehumidifier and a drainage problem.
2. The hygrometer log — establishes the patternA cheap hygrometer left in the space for two weeks, read daily. Above 60 percent through summer is condensation territory. Note whether the reading tracks humid weather or tracks rainfall — they are different causes.
3. The hose test — proves or clears exterior waterOn a dry day, run a hose at the ground beside the suspect wall for 20 minutes while somebody watches inside. If water appears, the source is outside and the fix is grading, gutters or drainage. If it does not, exterior intrusion at that point is unlikely.
4. The foil test on a slabTape foil tightly to a concrete floor for 24 hours. Damp under the foil means moisture is coming up through the slab; damp on top means it is condensing out of the room air.

The Timeline Question, and Why It Is Asked

An inspector will ask when things changed, and the reason is that most moisture problems in existing buildings start with an intervention rather than with deterioration. The list worth thinking about before the visit:

• A new roof — ridge vents added, intake unchanged
• New windows — the building's unintended ventilation removed
• Insulation topped up — soffits buried, surfaces colder
• The basement finished — a cold wall covered with organic material
• A humidifier fitted — moisture added all winter
• Landscaping or a new patio — grading changed toward the house
• An addition built — a new crawl space, a changed drainage path
• A period of vacancy or minimal heating

If a problem started within a year or two of any of those, that is where the investigation begins.

What Gets Missed Most Often in This County

• The rim joist. Almost never inspected, and in a Wisconsin winter it is the coldest wood in the building with a bare fiberglass batt pressed against it.
• Downspout discharge. A downspout ending at the foundation puts thousands of gallons a year within a foot of the wall. Extensions cost very little.
• Frozen downspouts and ice at the elbow. Seasonal, and it discharges directly against the wall for weeks at exactly the time the ground cannot absorb it.
• Bath fans terminating in the attic. The cheapest fix on this entire site, and one of the commonest faults.
• The dryer vent. Disconnected or leaking into a crawl space or basement. A dryer puts several liters of water into the air per load.
• A humidifier left running past March. Generates the moisture that then condenses inside the walls.

Frequently Asked Questions