To prevent mold before winter in Ann Arbor, spend a late fall weekend moving water away from the house and keeping moisture down inside it. Clean gutters after the leaves drop, shut off and drain outdoor faucets, test the sump pump, check grading, and set a dehumidifier to keep humidity below 60 percent once the windows close. There's a short window every fall when the trees along Ann Arbor's streets have mostly let go, the first frosty mornings have come and gone, and the ground hasn't locked up yet. That's the sweet spot for getting your house ready. You can still work outside comfortably, hoses still drain, and you can see exactly where water goes when it rains. Whether you live in an older house in Water Hill, near Burns Park or in a newer home across town, the job is the same. Mold needs moisture. If you take away the moisture before you seal the house up for winter, you take away most of the risk.
Why does fall prep matter so much for mold?
The EPA puts it simply: moisture control is the key to mold control. Every item on this list comes back to that idea. You're either keeping water from getting in, or helping the house get rid of the moisture it makes on its own. Fall is the turning point. All summer, open windows and warm air help a house dry out. Once you close up for winter, cooking, showers, laundry and breathing keep adding moisture, and there are fewer ways for it to leave. A problem you fix now is a problem you won't discover in March.
Your fall mold-prevention checklist
Here's the short version. Each item has a one-line reason, and the sections below walk through how to do them.
- Clean gutters after the leaves drop. Clogged gutters overflow right next to your foundation.
- Extend downspouts away from the house. Water should land several feet out, not against the basement wall.
- Disconnect hoses and drain outdoor faucets. A frozen line can split and leak inside a wall where no one sees it.
- Test the sump pump. You want to know it works before a late fall downpour, not during one.
- Check the grading. The EPA advises that the ground should slope away from the foundation.
- Set up a dehumidifier and a hygrometer. Indoor humidity should stay below 60 percent, ideally 30 to 50 percent.
- Test bathroom and kitchen fans. Moist air needs a way out once the windows stay shut.
- Look in the attic. Warm, damp air rising into a cold attic can condense on the roof deck.
- Clean the dryer vent. A clogged vent pushes humid air back into the house.
- Re-pack storage. Cardboard on a basement floor holds moisture all winter.
When should you clean the gutters?
Wait until most of the leaves are down. Cleaning in early October feels productive, but if the big oak next door hasn't dropped yet, you'll be back on the ladder in three weeks. Depending on the trees on your street, that can mean waiting until the very end of the season. Clear the troughs, then run a hose through each one to make sure water reaches the downspout. Watch the seams and corners for drips. A gutter that leaks at a corner can dump water in the same spot by the foundation every time it rains. While you're up there, look at the downspouts. Each one should empty onto a splash block or extension that carries water several feet away from the house. The EPA's guidance is to clean and repair roof gutters regularly, and this is the season it pays off most.
What should you do with outdoor faucets and hoses?
Disconnect every garden hose before nights start dropping below freezing. A hose left attached traps water in the faucet, and when that water freezes it can crack the pipe just inside the wall. You may not know until spring, when you turn the faucet on and water runs into the basement ceiling or the wall cavity instead of the yard. Many homes have an interior shutoff valve for each outdoor faucet, usually in the basement near where the line passes through the wall. Close it, then open the outside faucet to let the line drain. If you aren't sure which valve goes where, follow the pipe from the faucet's location inside. Also think about other exterior plumbing: irrigation lines, an outdoor shower or a utility sink in an unheated garage. Anything holding water in an unheated space is worth draining. A slow leak behind finished drywall can keep materials damp for weeks before anyone notices.
Is your sump pump ready for late fall rain?
If your home has a sump pump, test it now. Lift the lid and slowly pour a bucket of water into the pit until the float rises. The pump should kick on, empty the pit and shut off on its own. Then check where the water goes. Follow the discharge line outside and make sure it isn't clogged with leaves and empties well away from the house. A discharge that dumps right beside the foundation just sends the same water back toward the basement. Make sure the outside end won't freeze shut with water sitting in it. If the pump is old, noisy or slow, plan on replacing it before winter rather than after a storm.
How do you check the grading around your house?
Walk around the house during or right after a good rain. You're looking for water that pools near the foundation or flows toward the house instead of away from it. The EPA recommends making sure the ground slopes away from the building foundation. Flower beds are a common trouble spot. Over the years, mulch and soil settle and the edge closest to the house can end up lower than the lawn. Window wells and patios that have sunk toward the house are worth noting too. Small fixes, like adding soil to rebuild a slope or resetting a splash block, are easy to do on a mild fall afternoon.
What humidity should you keep once the windows close?
The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. An inexpensive hygrometer tells you where you stand. Put one in the basement and one on the main floor so you can compare. A dehumidifier in the basement is the workhorse here. Set it in the target range, empty the bucket or run the hose to a floor drain, and clean the filter. If you notice condensation collecting on windows, walls or pipes, the EPA advises drying the surface right away and reducing the moisture source. Wrapping cold water pipes with insulation helps cut down on that sweating. If you run a whole-house humidifier on your furnace in winter, keep an eye on it. Setting it too high can push humidity past the target range and lead to condensation on cold windows and exterior walls.
Are your bathroom and kitchen fans actually working?
Hold a single square of toilet paper up to the bathroom fan grille while it runs. If the fan pulls it against the grille, air is moving. If the tissue just falls, the fan or its duct may need attention. The EPA recommends running the bathroom fan or opening a window when you shower, and using exhaust fans while cooking or running the dishwasher. In winter, opening a window isn't always realistic, so the fan becomes the main way that steam leaves the house. Leave it on for a while after you finish showering. Also check where the fan sends that air. A bathroom fan should vent to the outside, not into the attic. A duct that has come loose or was never run to the roof or wall can leave wet air sitting in the attic all winter.
What should you look for in the attic?
Take a flashlight up on a dry fall day. Look at the underside of the roof deck and the rafters for dark staining, frost marks or water drips. Check that insulation isn't blocking the soffit vents along the eaves, and that bath fan ducts are connected and run outside. The main concern in winter is warm, moist air rising from the living space into a cold attic, where it can condense on the roof sheathing. Gaps around light fixtures, the attic hatch and plumbing stacks let that air through. If you see staining or a damp, musty smell up there, it's worth having someone take a closer look before the snow comes.
Why does the dryer vent matter?
A clothes dryer moves a lot of moisture. The EPA advises venting moisture-producing appliances such as dryers to the outside. If the vent is clogged with lint or crushed behind the machine, some of that humid air ends up in the laundry room instead. Pull the dryer out and check the duct for kinks or tears. Go outside and make sure the flap opens when the dryer runs and isn't packed with lint. If drying times have gotten longer, a clogged vent is a common reason. Mold Medics also offers dryer vent cleaning if the run is long or hard to reach.
How should you store things for winter?
Basements and garages fill up in fall with patio cushions, holiday decorations and kids' summer gear. Cardboard boxes on a concrete floor soak up moisture and give mold an easy place to start.
- Swap cardboard for plastic bins with lids.
- Keep bins off the floor on shelving, even a few inches up.
- Leave a gap between stored items and exterior walls so air can move.
- Make sure cushions, tents and sleeping bags are fully dry before packing them away.
- Don't block the dehumidifier or floor drain with storage.
What if you find mold while doing this list?
It happens. You pull a box away from the wall or open the attic hatch and see spotting. The EPA says that when the moldy area is less than about 10 square feet, you can usually handle the job yourself. Fix the moisture source too, or it will come back. Don't paint or caulk over it. The EPA specifically advises against painting or caulking moldy surfaces, because the paint is likely to peel and the growth is still underneath. Absorbent materials like ceiling tiles and carpet that have become moldy may need to be thrown away. If the area is larger than that, keeps coming back, or you smell mold but can't find it, a professional look makes sense. A visual inspection with a thermal imaging camera and a moisture meter can show damp areas behind walls and under floors that you can't see with a flashlight. If you've had a leak, remember the EPA's advice to dry water-damaged materials within 24 to 48 hours.
How does this list fit an Ann Arbor house?
Ann Arbor has a wide mix of homes, from older houses in the Old West Side and Burns Park to much newer construction. The checklist works for all of them, but the priorities shift a little. In an older house, spend extra time on the basement walls, the exterior faucet lines and any bathroom fan that was added during a remodel, since those are places where older and newer work meet. In a newer home, the basics tend to be in better shape, so the bigger wins usually come from habits: running the bath fan long enough, keeping the dehumidifier emptied and making sure storage doesn't crowd the walls. Either way, a walk around the outside after a fall rain will show you more than any list can.
Get ahead of it this fall
A few hours of fall chores can save you from a winter of damp corners and musty closets. If you work through this list and find something that doesn't look right, or you'd just like a second set of eyes before the cold settles in, book a free visual mold inspection with Mold Medics Ann Arbor.
