Foundation interior drainage systems are one of the most important aspects of residential construction. Drain tile systems are also one of the most misunderstood aspects. Because these systems are buried and cannot be easily modified or corrected, it is vitally important that they are installed correctly.

Foundation drainage systems, which are installed properly, can serve a dual role. Foundation drain tile systems are the means by which groundwater can be transported away from your basement. If you want a dry basement and a sound foundation, you must have an adequate foundation drainage system. The water content in the soil surrounding your house can fluctuate seasonally. There is always a point at which you can dig and hit water. Geologists often refer to this as the water table. This water table rises and falls in response to the amount of precipitation in any given time period. The water table in many parts of the country can rise to within a few feet of the surface during wet spells. Water will take the path of least resistance. If there is no exterior waterproofing water can go sideways through a crack in your foundation, or it can go down alongside your foundation into a pipe. I'm sure that you will agree that it is a better idea for the water to go down into the pipe.

Interior drainage systems work extremely well for many customers. Depending on your circumstances, this may be an effective solution. Many water control system companies claim to be waterproofers and offer this method as a solution to every basement water problem. If a company proposes opening the floor on the inside for any reason, they are offering an interior drainage system. Only an exterior excavation to the footer or bottom of the foundation accomplishes waterproofing. Never contract for a water control system if dampness, seepage, and or cracking on the walls are your concern, as this may result in further damage to your foundation.

To de-water a basement from the interior, a perimeter drain must be installed. In cases where water is coming up through the floor, we prefer adding lateral (front to back) drain pipe to collect water before it comes in contact with the underside of the slab. The water is  transported away from the basement, preventing floor water, and flooding. If a basement has a concrete slab floor this will entail breaking the floor at the walls and/or across the floor and installing drain pipe that leads to a sump-pump or gravity drain, and then re-pouring the broken sections of the floor. If grade conditions and slope of land are adequate to accommodate a gravity drain, or you build on a hillside, your drain tile pipe will simply 'daylight' or come to the surface. It is a much more reliable system, as you do not have to rely on electricity to discharge the water in a torrential rain, your system depends entirely on gravity to work. If you build on level ground, you have basically two choices, install a sump pit or a large buried french drain.  A french drain pit is a large subterranean pit filled with gravel. The drain tile pipe runs to this pit and the water fills this pit. French drains do not work well in areas where the water table rises above the level of the French drain pit or the basement floor. A sump pit is installed inside the basement of your home. The drain tile pipe runs to this sump. The collected water is then mechanically pumped from the sump and away from the home.

The National Waterproofing Systems process starts with opening the floor at the base of the wall and installing drain pipe at the proper depth, we always use schedule 35 perforated PVC. We begin with laying a non-deteriorative geo-textile fabric on the soil next to the footer. A two or three-inch thick layer of clean gravel is then spread on top of the geo-textile fabric. The pipe is enclosed in a spun bonded filter sock and placed on top of the gravel beside the concrete footer. Drain tiles work most effectively when placed deep and next to the foundation footer, instead of on top of the footer. This practice allows you to lower the effective water table an additional 6-8" below your basement floor. (contrary to what many water control system companies, who exclusively install on top of the footer systems, would have you believe)

Note: Above or on top of the footer installations allow the water table to rise high enough to contact the underside of the floor slab. This can cause structural deficiency, seepage through floor cracks, excess humidity and mold infestation in a basement. This method also allows a greater chance  of complete failure in areas that are experiencing extended periods of heavy rain.

A coarse aggregate is then placed around the drain tile pipe. The gravel must be shrouded with the geo-textile fabric, this covering keeps the gravel clean and allows the water to flow into the system freely.

Another critical component of this system is the dimpled membrane placed against the base of the wall and beneath the slab along the top of the gravel, before the new concrete is poured. In situations where exterior waterproofing is basically impossible, the dimpled sheeting permits free drainage down the wall and across the footing into the drain pipe. This membrane also prohibits water vapor from penetrating the underside of the floor slab, which would otherwise produce excess humidity in the basement and cause damp spots on the concrete floor to occur during heavy rain.

Drain pipe gravity feeds the water into a sump, which houses a heavy-duty submersible pump. In keeping our philosophy of always using the highest quality materials, National Waterproofing Systems utilizes top of the line, alarmed, battery backup, fully automatic, dual Zoeller sump pumps in all  our interior drainage systems. They are quiet and long lasting. The primary pump is a high quality ½ hp Zoeller sump pump backed by a secondary battery operated, high capacity, non-corrosive Zoeller pump if the primary pump ever fails due to a power outage or mechanical failure. All pumps have battery burn out and overcharge protection. No other interior drainage system offers the reliability and protection we provide when the primary pump fails due to damage or mechanical malfunction, or when the primary pump fails to keep up with excessive water due to heavy rain or overloading.

95% of our foundation drainage system business is installing retrofit systems ... replacing other systems that have failed. Most are less than 5 years old.

When an Interior pressure relief foundation drainage system is installed properly using the highest quality materials, it will last the life of the structure.

Why Interior Drainage Systems?

In some cases the process of installing an interior drainage system is less expensive and evasive then exterior waterproofing. A perimeter drainage system will still prevent unsightly water on a basement floor and flooding, but will not eliminate seepage if there are cracks in the foundation walls.  

Never contract for a water control system if dampness, seepage and or cracking on the walls are your concern, as this may result in further damage to your foundation.

An interior drainage system does not waterproof a basement. For more information on our industry leading, superior multi-layer exterior foundation sealing process please see the Exterior Waterproofing section. Standing water and heavy moisture can lead to an infestation of mold, mildew and fungus on the joists, studs and sheetrock in the basement, not only can mold lead to wood-rot and costly repairs, it can be quite damaging to your health. If mold is present, or if you are unsure whether or not your wet basement has promoted unseen mold growth, National waterproofing Systems certified mold inspectors and remediators can inspect and remove the mold spores, mildew, fungus, toxins and dead organic material from all surfaces, apply a superior mold resistant coating, and install a moisture control unit to prevent any recurrent mold growth in the future.

For more information about an interior drainage system for your basement, mold removal, total moisture control and indoor air quality solutions, or to schedule a FREE inspection please contact us.  1.888.460.SEAL  1.888.460.SEAL