Start with the symptom, not a diagnosis
What you can actually observe: “Wet spot lower left corner of window 7 a.m.,” “Ceiling stain darkens after shower upstairs” or “Musty odor when room closed overnight.” There’s a bad pipe in the upstairs bathroom. There’s water dripping from the ceiling in the upstairs bathroom. The log is supposed to be testing for patterns.
Record five fields every time the condition appears
| Field | What to write | Why it helps |
|---|---|---|
| Date/time | When you observed it | Shows recurrence and duration |
| Exact location | Same corner, joint, ceiling mark, floor edge | Prevents different symptoms being combined |
| Recent event | Rain, shower, washing machine, cooking, HVAC use | Provides possible triggers |
| Indoor condition | Humidity/temperature if measured; ventilation state | Helps identify condensation patterns |
| Change from last entry | Larger, smaller, drier, new odor, new material affected | Shows whether the condition is stable or progressing |
Photograph from the same position
A repeatable reference point and, if possible, a ruler or other scale. Name photos by date, not memory. If the edge of a stain changes, a set of consistent photographs is more valuable than a few close-ups taken from different angles.
Don’t open up walls or disturb potentially hazardous materials just to improve the record. The log should make no disturbance, nor should it create any.
Recognize 4 common moisture patterns
1. Water-related events
The symptom occurs immediately after a specific event, such as a shower, appliance cycle or rain. Repetition after the same event reinforces the link, but by itself cannot pinpoint the exact failed component.
2. Moisture from Condensation
Under certain temperature/humidity conditions water will condense on colder surfaces, usually windows, pipes or thermal bridges. Pattern varies by ventilation and season. Some context can be added by measuring the humidity inside . What is acceptable is a function of climate and construction .
3. Persistent moisture
Material remains wet with no apparent event. This should be investigated immediately as there may be hidden water, ground moisture or some other source that is on-going.
4. Spill or settled event, one-off
After a known incident, the area dries and does not recur. Watch until you are certain the material is back to normal and no secondary damage is occurring.
Moisture control is important. The US EPA says that controlling indoor mold is all about moisture control and recommends that wet items be dried promptly following water events. See its guide to home moisture and mold. This is US guidance, local health/building advice may vary.
Use a seven day pattern table
Example log
Time ObservationIndoor RH Recent event
Mon 07:10 Condensation on bedroom window on lower levelRoom closed overnight 68%
Tue 7:00 AMSimilar condensation Room closed over nite 66%
Wed 07:05 Little DewLeft door open; ventilation used 55%
Heavy rain 56% Thu 19:20 No rain
This pattern does not prove that the window assembly is sound, but it is a better starting point than “the window leaks.” Currently the symptom is more closely tied to indoor conditions than to rain.
Escalation triggers Mark
Don’t keep logging forever while damage accumulates. If you see active or increased water entry, soft or deteriorating material, electrical involvement, contaminated water, large affected areas, repeated mold growth, structural movement or a condition that you cannot safely inspect, escalate. A qualified professional can use a short log to see the timing, but it is not a substitute for urgent action.
Don’t paint out the evidence too soon
Cosmetic repair can mask clues. Before covering a stain, be sure the source of the stain is handled, and the material is in a state of being repaired. Keep the photos and dates even after the area dries so you can compare if the symptom returns.
Moisture-log template (printable)
Date & Time:
Specific Room/Location:
What I can see/smell/feel:
Approx. dimensions:
Recent rain/weather event:
Recent use of plumbing/appliance/shower?
Indoor humidity/temperature if measured:
Ventilation/HVAC status:
Photo file name:
Change since last entry:
Action taken:
Hit the escalation button? Yes / No
Use the log as part of a monthly inspection routine
The monthly moisture check provides a routine check of all rooms. This page’s log is for one particular recurring symptom. Together they help to differentiate between broad preventive checks and focused investigation.
The goal is better evidence, not diy diagnosis at any cost
A pattern log helps you narrow down possibilities and explain a problem clearly. It should also tell you when the condition is getting bad or beyond the bounds of a safe homeowner inspection. Record enough to improve your next decision. Act on what the pattern indicates.