Print this page or save it to your phone. Walk your house once, check each box, and you'll know where moisture is hiding before it turns into a problem.
Part 1: Know your numbers
Most homes do best between 30% and 50% relative humidity. In cold weather, aim lower (about 30–40%) to keep windows dry.
| Reading | What it means | What to do |
|---|---|---|
| Under 30% | Dry. Static, dry skin, cracked wood. | Ease off dehumidifiers; consider a humidifier. |
| 30–50% | Healthy range. | Keep doing what you're doing. |
| 50–60% | Watch zone. | Run fans longer, check for leaks, improve airflow. |
| Over 60% for days | Too wet. Conditions where mold can grow. | Find the source; use a dehumidifier; fix leaks. |
Part 2: Where to measure (5 minutes)
Check each room with a hygrometer, ideally at the same time of day:
- ☐ Main bathroom, 20 minutes after a shower
- ☐ Basement or lowest level
- ☐ Crawlspace access, if you have one
- ☐ Bedroom with the coldest windows
- ☐ Laundry room
- ☐ Closet on an exterior wall
Write the readings down. Any room over 60% is your first project.
Part 3: The 8 leak spots to check (5 minutes)
- ☐ Water heater: any water in the pan or on the floor?
- ☐ Kitchen sink: look and feel under the cabinet floor
- ☐ Bathroom sinks: supply lines and drain fittings
- ☐ Toilets: base and supply valve
- ☐ Washing machine: hoses and the floor behind it
- ☐ Dishwasher: edges of the floor in front
- ☐ AC air handler: standing water in the drain pan?
- ☐ Fridge with ice maker: the water line behind it
Part 4: Outside, before the first freeze
- ☐ Disconnect garden hoses
- ☐ Shut off and drain outdoor spigots
- ☐ Clear gutters
- ☐ Point downspouts 4–6 feet away from the foundation
- ☐ Know where your main water shutoff is (and that it turns)
Part 5: Make it automatic
- ☐ Change your HVAC air filter every 1–6 months (schedule here)
- ☐ Flush the AC drain line every 1–3 months in cooling season (how-to)
- ☐ Put a Wi-Fi leak sensor at the water heater and under sinks so your phone alerts you
- ☐ Put a Wi-Fi humidity sensor in the room with your highest reading
This checklist is general home-maintenance guidance. If you see active mold over a large area, water you can't trace, or anything electrical near water, call a qualified professional.
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