Downspouts discharging above grade are easy to repair or replace if they become damaged or clogged. It is also easy to know whether the gutters and downspouts are working properly during a rain, just by watching the discharge from the downspout extensions. Nonperformance can be quickly identified and cured inexpensively. Downspouts should discharge at least six feet from the building, and the ground at the discharge point should slope slightly (one inch per foot, for example) away from the building. Common problems include downspouts that discharge too close to the building, or discharge where the ground slope directs water back against the building wall.
One of the other advantages of long downspout extensions is that after the water has moved nearly horizontally for 6 feet or so it will not damage most landscaping.Shorter downspout extensions may require splash blocks to avoid digging holes in lawns and gardens. Splash blocks are often too small. They tend to get moved around, and may settle, sloping back toward the house.
The disadvantages of discharging onto the ground can be traffic problems at building corners (people may trip over downspout extensions), and the necessity to temporarily disconnect or lift downspout extensions when cutting the grass. Some people also feel the downspout extensions are unsightly.
Another disadvantage of using the above-grade downspout extensions is that they can dump a fair bit of water onto the property near the house. Even if the water does not get into the house, it can pool if drainage is poor. In freezing climates, the ponded water may create ice on sidewalks, patios and driveways, creating a slip hazard.
The causes of ineffective downspout extensions include
The implications include damage to the lower section of the building and moisture getting into the basement or crawlspace.
Effective downspouts have