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Anyone who has coped with rain-soaked plaster and flooded basements can be forgiven skepticism when a professional roofer speaks of hundred-year-old roofs that, although they leaked daylight in a dozen places, let in hardly a drop during a rainstorm. The story is not an exaggeration. Many older roofs are covered with wood shingles, which have the happy faculty of plugging their own small leaks. The wood expands as it absorbs the initial rainfall, effectively sealing small holes. Unfortunately, the leaks and moisture problems en countered by modern homeowners go beyond small holes and are rarely self-correcting; prompt action must be taken before water causes serious and expensive harm.
In addition to such obvious effects as puddles and peeling paint, water can cause damage more slowly and in less noticeable areas. An ice dam on the roof often hides water seeping under shingles. The swelling and shrinking caused by changes in moisture levels makes wood joists and beams warp and bow. Damp timbers are susceptible to the fungi that cause mold, mildew and dry rot—which can reduce sturdy beams to dry powder; damp wood near the foundation also invites termite infestation.
Keeping the house dry is a twofold task. On the outside, water must be channeled off the house and away from the foundation. In side, water vapor—moisture that's not in liquid form but is in the air as humidity—must be carefully controlled. Some water vapor enters the house with humid outdoor air, but enormous amounts are generated inside the home by bathing, cooking and laundering.
Most condensation problems can be cured by improving the ventilation in your home. By installing strategically placed openings in the attic and basement, you can ensure a constant movement of air that will push warm moisture outdoors, taking advantage of hot air’s natural tendency to rise. In problem areas such as kitchens, bathrooms and laundries, electric fans and ducting may be necessary. An electric dehumidifier can also help.
Leaks and seepage originating outdoors can often be corrected by such simple measures as redirecting the flow from downspouts and banking the earth around the foundation. If the basement still leaks, try waterproofing the porous masonry from the inside with the appropriate paint, sealant or cement. More serious drainage problems, or a rising ground-water level under the basement, will require digging a dry well or excavating around the foundation to install drain tile and waterproof the exterior walls. When even these measures fail to keep water out of the basement, an electric sump pump provides the last line of defense, discharging the water as fast as it enters.
TIP: A splash block keeps a basement dry. The solution to basement dampness is often simple and inexpensive. If your downspouts discharge rain water and melting snow directly onto the soil around the foundation, that water may be reappearing as seepage on basement walls or as puddles on the floor. Installing a masonry splash block under the downspout and tilting it to channel water away from the house will often cure the dampness for only the cost of the block.
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