Homeowners often ask, "what's the difference between an exterior system and an interior system?" and sometimes quickly followed by "well, then why not just install an exterior system?"
Both very good questions - Let's address them.
An interior waterproofing system is a system that installed on the inside of the basement. They typically run along the perimeter of the basement, and in the example of Pioneer Basement's Grate Drain system, it comes complete with sealed vapor barrier, sump pump, sump basin and all the piping for removing the water from the system.
Exterior systems, as the name suggests, are installed around the foundation on the outside. Depending on the design by the contractor, it would normally include a pipe with holes (to allow water in) a type of geo-tech fabric to filter out soil, and crushed stone. They don't typically include pumps, and are gravity fed to a low point in the landscape.
In a perfect world, both systems would be installed on every new home built in the country, but the truth is, they aren't.
Basics of their Functions
Exterior systems are designed to channel the water away from the foundation and move it to a spot where it can be absorbed by the soil.
Interior systems are designed to trap any water that gets through a repair, foundation or separation and pump it back out of the system and into the landscape.
Exterior systems are surrounded by soil, rodents, insects, rocks and other things that can clog or dislodge the drain. Over time these drains will clog and stop working, which will result in leaks and flooding which it was designed to protect. Life expectancy is 5-10 years.
Interior systems, by being installed on the inside of the home, take care of water coming in from all angles, under the floor, from behind the wall, or from the separation between the wall and the footer of the home. With proper installation and proper maintenance these systems can last the life of the house.
Why do you need maintenance?
Exterior systems rarely have access points from which you can flush the system out. Because of this the systems get clogged faster and become a problem source, rather than a problem solution.
Interior systems, most of the new designs like the GrateDrain from Grate Products, come with access points that allow service men to clean and maintain the flow of the system. This in combination with sump pump maintenance can increase the life of the system, the pump, and the dryness of the basement.
How would each affect me finishing off the basement?
Exterior systems won't affect the way you finish the basement, but it will affect the way you live in the space in 5-10 years. With possible problems down the road, a basement with an exterior system only isn't ready to be finished and a serious investment shouldn't be made in the space.
Interior systems simply require that your finished walls be installed 1-2" away from the foundation, which won't change your floor plan that much. Finishing the basement with this method should also include using in-organic material such as metal studs and mold/moisture resistant dry wall for best results. After finishing install a dehumidifier to provide circulation and over all moisture/humidity control for your finished space.
Related Reading and Links
Read about the Top 6 Basement Mistakes that contractors and homeowners make. See what other readers have asked in Safe'n'Dry Basement Blog's Reader Questions Section
Ask Jacob A question Directly on Pioneer Basement's Help Forums!