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 encountered by modern homeowners go beyond small holes and are rarely self-correcting; prompt action must be taken before the 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 make 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. Inside, water vapor—moisture that is 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 rainwater 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.
Channeling Water Away from Your House
Water that collects around the foundation of a house can exert tremendous pressure—as much as 500 pounds per square foot—eventually causing structural damage and wet basements. Channeling rain and melting snow away from the foundation is thus a primary concern of every homeowner.
You can protect a house located on the sloping ground by digging a system of swales—drainage ditches that are planted over with grass and are so shallow they are almost unnoticeable—to collect most of the runoff and reroute it away from the foundation. Rain that falls within this defensive line can be deflected by banking earth near the house to form a sloping watershed. If the dirt would cover part of a basement window, install a window well. Do not pile dirt closer than 8 inches to wood siding, however, or insects will use the embankment as a bridge into the house. Areas directly below eaves must be protected from water coursing off the roof; raindrops can erode soil and expose the foundation. Gutters and downspouts are the common means by which this water is carried away. But these conduits are not the only solutions; indeed, they have drawbacks that the homeowner should keep in mind. They need maintenance—painting, patching, repositioning—and replacement when they wear out. They get clogged with debris. In northern climates they become blocked with snow and ice, causing buildups on the gutters and the roof itself.
Use gutters and downspouts where they are essential, but let rainfall freely off the roof if the ground below will bear it. A steep embankment often is protection enough. Thin strips of gravel, walks, and patios are better still. And dense shrubbery planted under the eaves not only impedes erosion but adds a note of grace to your landscaping. Be careful, though, to avoid greenery with large root systems; the roots may grow against the foundation and crack it.
Wherever downspouts are used, the area around them must be given extra protection from the heavy concentration of water they spew forth. If the ground slopes sharply, you may need to install only a splash block that will absorb the impact and disperse the torrent. But if the house is on level ground you probably will need a downspout extension. This may be as simple as a coiled plastic pipe that unfurls under the force of running water, or it may involve underground piping and, in extreme cases, a dry well. Again, be guided by the rule that the best system is the simplest one that will get the job done.
Installing a window well
The cavity around a basement window that extends below ground level exposes the foundation to serious water damage unless proper drainage is provided. The solution is a window well. The liner of an inexpensive and easy-to-install well consists of a ready-made, oval-shaped sheet of galvanized steel, usually corrugated. Available at building- supply stores, the sheets come in a variety of sizes that will fit around almost any window.
Buy a liner 6 inches wider than the window. Dig a hole for the liner 1 foot deeper than the bottom of the window. Center the liner in the bottom of the hole. Spread 4 inches of gravel on the bottom of the well, both inside and outside the liner, then fill the rest of the hole behind the liner—away from the house—with earth. Plant sod or place a thin strip of gravel on top of the earth so that rain falling around the perimeter of the well will drain away naturally.
A System of Swales and Berms
Laying out drainage ditches. Plan ditches—swales—across the slope above your house to intercept water coming downhill, making them long enough to divert the water around the foundation. The downhill house in this picture requires only a single curved ditch to keep the basement dry. The uphill house needs a more elaborate system of connecting ditches to direct water away from its downhill neighbor.
Digging a drainage ditch. Make your ditches 2 to 3 feet wide and 6 to 10 inches deep. As you dig, pile the dirt on the downhill side of the ditch to make a lip—a berm—to help trap water in the ditch. Next, spread 2 or 3 inches of gravel in the ditch, then fill in the rest of the way with topsoil, leaving the downhill lip. Place sod over the lip and plant long-rooted grass such as Bermuda in the ditch to hold the topsoil and gravel in place.