Ways To Properly Divert Water
Above-ground plastic extensions -- Better than nothing but not much. If these 3 - 4 foot hardware store extensions are properly installed and maintained and are long enough, they can divert water away from a foundation. Too often, however, these extensions are knocked off the downspouts by kids, pets or landscapers, or fall off on their own, leading to water being dumped next to the foundation.
The extensions typically sold in hardware or big box stores are too short to help much but, if the homeowner is savvy enough to realize this and installs longer ones, his house resembles a giant octopus with its arms extending to the middle of the yard. Nice look, huh?
Downspouts that lead away from the house -- This is almost always the preferred choice. When properly installed, an underground downspout extension is permanently attached to the downspout and it is guaranteed to carry the water far from the foundation. Fitted with a debris filter, the underground extension ensures a free flow of rain water to one of several destinations.
Often, underground extensions will connect to storm sewers, although many municipalities now discourage this practice to prevent back-ups. The preferred option is to send the water along the slope of the land to an open discharge point, but slopes are few in this part of the country. The best option may be connecting to dry wells or bubbler pots that collect discharged rainwater and allow it to escape in moderate amounts.
The next time it rains, get an umbrella and go outside to see where all that water is going when it leaves your downspouts. If your home looks like one of the first two situations above, you need some help to prevent foundation problems before they start.
If you are buying a home and your home inspector brings this issue up I hope I have made things clearer to understand. A good home inspector, or good home inspection company should help identify and water intrusion issues found throughout the home inspection process.