Dampness isn't just uncomfortable, it can be a serious problem for you and your house, promoting the growth of mold and other microorganisms that can cause illness and structural damage. Moisture is in the air all around us, and a certain amount is necessary for comfort, but if your house feels excessively damp, it may be time to do something about it. Dampness can come from above or below, and it usually develops in the absence of proper ventilation.
Moisture can rise through the floor and foundation by capillary action. It comes from damp concrete and poorly drained ground, and besides making the basement and lower stories uncomfortable, it can damage the floors, foundation and other woodwork. It's most common in buildings with concrete foundations or poorly ventilated crawlspaces.
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- Improve drainage around the house by installing French drains or redirecting runoff from the gutters.
- Provide air exchange in the crawlspace, using active methods, such as fans, if necessary. Note that sealed crawlspaces require different techniques than ventilated crawlspaces.
- Install a moisture barrier on the ground in the crawlspace.
Dampness on the walls is often due to condensation that collects because of the temperature differential between the inside and outside of the house. Moisture in the house can come from many sources, including:
- The bathroom -- especially the shower.
- The kitchen.
- The laundry room -- particularly the dryer.
The problem is worsened by the lack of proper ventilation. When the moisture-laden air condenses on the walls or the back of the toilet, mold and mildew are virtually inevitable.
Properly insulating the walls is a good way to prevent condensation, but that alone won't solve the humidity problem. To do that, you need to:
- Improve ventilation -- Open windows when practical, run your central air system more frequently or use fans to introduce fresh air into the house. Consider a heat recovery ventilator (HRV) or energy recovery ventilator (ERV) if your home is built to high energy-efficiency standards.
- Run a dehumidifier -- In cases in which providing proper ventilation is impractical, running a dehumidifier may be the best alternative.
- Vent your dryer -- If your dryer is creating moisture, it's because air isn't being properly vented to the outside. If the vents are properly installed, they are probably filled with lint and need to be cleaned.
- Use your bathroom's exhaust fan -- You should turn on the exhaust fan before you get in the shower and leave it on for at least 10 minutes after you get out. If you don't have an exhaust fan in the bathroom, open a window.
Wall and Roof Penetration
Your house may be damp because of one or several leaks in the roof or walls. Leaks can be subtle -- you may not realize you have one until the wall or ceiling turns moldy or begins to buckle. Once that happens, it's a good bet the framing is soaked and adding to your home's humidity.
- Check the attic for signs of leaks, including discolored plywood on the ceiling and moldy insulation on the floor. Note the locations, and hire a professional to make repairs to the roof as necessary.
- Investigate any drywall damage or musty smells by removing drywall -- if necessary -- and looking for water damage in the framing. Trace the source of any leaks and seal the roof or siding as necessary.
- Caulk windows and doors around which you see the signs of moisture damage, including peeling paint, rotting wood or mold discoloration.
Like wall and roof leaks, plumbing leaks may not be immediately noticeable, and the first indication you have one may be wall or ceiling damage or mold. Once you know where to look, though, plumbing leaks are usually easier to pinpoint than wall or roof leaks, and the repair strategy is usually self-evident.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker and Family Handyman.