Overflowing gutters can flood basements, damage foundations and rot flooring from stagnant, moist pools of water under your house (and cause wood flooring to buckle and warp)
It's possible to prevent overflowing gutters. Here's how:
- At a minimum, clean out the gutters and downspout outletsbefore heavy rains. At least make sure that the downspout outlets are clear so water can leave the gutters.
- Stuff a sock or something in the downspout outlet when cleaning gutters to prevent gutter debris from clogging the downspout. Tie a red string to the sock and hang it over the edge so you don't forget to remove it. It would be disappointing to clean out the gutters and then have them overflow because you forgot to remove the sock!
- Make sure the elbows of down spouts are free from obstruction by pouring 2-3 gallons of water down them suddenly ( be careful with this weight on a ladder)
- If downspouts have sharp elbows, replace the downspout with one that is made to have rounded or elbows that are not sharp. Sharp elbows or tight corners in downspouts will restrict water and are the first places that gutter debris will clog.
- Make sure the drains that lead water away from the house are not flooded. Pour a full 5 gallon bucket of water down them suddenly to see if they back up. This won't guarantee that they won't back up, but may give you an early indication.
- Replace old, rotting iron drain pipes on older homes (many replace them with 3-5 inch black ABS drain pipe
- Don't install restrictive gutter covers that will allow water to "sheet" over them (or shoot over them) in a really heavy rain. It is during the heaviest rains that you depend on your gutters the most.
- Use a gutter size that is large enough for the roof area that drains into them.
- If downspouts clog easily, install a larger downspout outlet and/or increase the size of your downspout. A rectangular outlet and corrugated 2x3 downspout is adequate for most homes.
- Make sure the ground around your house slopes away from the foundation for at least 5 feet. This way if the gutters overflow, the water will hit the soil and the run-off will go away from your basement, foundation and house.
Also, for more information for preventing flooded basements, see Preventing flooded basements
These preventative steps will solve the most common reasons of why gutters overflow in heavy rains.