Waterproofing is the technique of repelling moisture from portions of the home in order to prevent water damage. Key areas especially vulnerable to such damage are roofs, decks, and basements.
Roofs are usually threatened by ice freezing along the peripheries of the building, which dams up rain and forces it to seep between shingles and into flaws. Most roofs possess a felt paper covering beneath the shingles to serve as a barrier against water, but this covering is often inadequate. An effective supplement is the use of special rubber-based sheets, which, in addition to being watertight themselves, often possess trace specks of glass that help to resist ultraviolet light as well as moisture. Such sheets are purchased by the roll and are laid over the eaves and peak of the home where ice damming tends to occur, preventing future cases of water buildup. They are usually stapled into place or stuck down with an adhesive. Such a system is relatively easy to install, and fairly inexpensive.
Decks can often be the most vulnerable structures in any home. No other purely wooden component of a building receives quite so much exposure to the elements, and decks are often seriously damaged by rainwater which settles on the flat surface and gradually soaks into the wood. Decks should therefore be coated with a sealant specially designed to resist water. Such sealants can often cause a fading of the wood, especially oil-based sealants, which tend to breed algae and mildew. It is thus usually preferable to use synthetic-based sealants, which are longer-lasting and attract fewer invasive organisms.
For further information on protecting your deck see the following article from HomeDoctor.net: Waterproof Decking at Home.
Basements are frequently difficult to waterproof because the source of the water damage is not always readily apparent. To determine whether moisture is coming from an exterior leak or the condensation of water within the basement itself, one commonly applies a sheet of water-resistant material such as aluminum against the problem wall, sealing it tight and letting it sit for several days, after which one can glean the source of the moisture by noting which side of the sheet is damp. An external leak may be the result of slanted landscaping or poorly designed gutters, which direct water towards the basement walls where it seeps in through hair-thin crevices. It is often easiest simply to alter the slope of the ground or the positioning of the gutter than to attempt to repair minor flaws in the wall. Internal condensation is usually caused by moisture released from plumbing which runs through the basement; this can frequently be addressed by applying additional insulation to the pipes.