Here is a realistic and inexpensive way to take care of roof drainage water. It's not fancy, but it tends to work as well, if not better, than the expensive interior or exterior perimeter drain system.
I have seen this type of system make a dramatic difference in most existing homes with wet basements. It is of greatest value when it replaces old concrete or clay in-ground drain systems, where an off-site system in not available or in homes without any downspout drain system.
Here is a good example of the type of excavation required for an on-site downspout drain system. The actual hole - the energy dissipation basin or "French drain" - must be at least 8' away from the foundation and the trench for the drain line must slope down and away from the house.
Once the filter cloth, gravel and drain tile is installed, the sod can be re-installed on a layer of filter cloth.
Corrugated drain tile has two advantages: price and length (250' rolls). However, this material tends to collapse easily and is harder to clean. Solid 4" plastic pipe tends to be a much better product. Since much of the cost in installing this type of system is in the labor, it makes sense to spend the money on quality material and make sure that the system is easy to maintain and lasts for a long time.
Corrugated and solid drain tile materials come in perforated and tight-line models. The perforated material should be used in places where the drain pipe is intended to absorb ground water, e.g. at building perimeters. Downspout must be directed to tight lines that move the water away from the foundation of the house.
Any drain tile with a run of over 20 feet should be installed with one or more clean-out locations. A clean-out is created by installing a "T" in the drain tile line. A riser is then installed into the "T". The portion of the riser which sticks out of the ground should be capped.
We often see attempts to correct basement moisture by elaborate and very expensive interior drainage systems. While such systems may be called for in some extreme cases, most are of questionable value. In any case, a good downspout drain system is a vital component to