Sunday, August 7, 2011

Interior Drainage Systems

Moisture problems in existing basements are very common, but often are not understood or properly treated. In a basement that is seldom used and separate from the living spaces above, this may not present a great problem. However, most basements are connected to the rest of the house. In addition, basements are increasingly used as finished living and bedroom spaces. In these cases, moisture problems are not only annoying and uncomfortable, but can lead to significant health problems. Molds and mildew can grow in damp carpets and beneath wall coverings. Finishing a basement without first dealing with the moisture problems can result in making health conditions worse and lead to significant damage as well.

Why Interior Drainage Systems?

Interior drain tile systems are one of the most important aspects of residential waterproofing and moisture control. 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 very important that they are installed correctly.

In many cases the process of installing an interior drainage system is less expensive and less evasive then exterior waterproofing. A perimeter drainage system will still prevent unsightly water on a basement floor and flooding, but may not eliminate seepage if there are cracks in the foundation walls. Cracking basement walls will need to be injected with epoxy or polyurethane. If cracking is significant, an exterior waterproofing system should be installed.

An interior drainage system is not waterproofing. Interior drain systems are water management agents that relieve excess water from around and under your foundation.

Interior Drainage Systems - Below the Slab

The most effective of the interior drainage systems is a perforated drain pipe installed inside the perimeter of the footing. Not only are these the most popular systems, they are also building code approved when installed correctly. This requires removing and replacing concrete around the slab edge. By placing the drain pipe beneath the slab, it drains the area to a lower level. Similar to an exterior system, this drainage pipe connects to a sump pump system. The sump basin should have an airtight, childproof cover. A critical component of this approach is the dimpled plastic sheeting placed at the base of the wall and beneath the slab edge. Dimpled sheeting is similar to a small egg crate and permits free drainage at the base of the wall into the drain pipe. It is less expensive than many specialized drainage channel systems. This system will remove rising groundwater if there is an aggregate layer under the slab.

It is recommended that this approach be combined with an active soil gas management system that connects with a sealed sump basin and perimeter drain pipe. This type of system will actively remove soil gases, such as radon and remove them from the living space. You should always consult with a radon specialists before any radon remediation is attempted.

Foundation drain tile systems are the means by which groundwater can be transported away from your basements foundation and floor. If you want a dry basement and a sound foundation, you must have an adequate foundation drainage system. Interior drainage systems work extremely well for many homeowners. Depending on your circumstances, this can be an effective solution.

Interior Drainage Channel - On Top Footings

The simplest and least costly approach to interior drainage is a drain channel adhered at the base of the wall, on top of the footing. Water is collected and drained into a sump basin. The sump pit should have an airtight, childproof cover. These types of systems do not solve the problem in masonry walls because water remains in the block cores at floor level and the water level is only lowered to the top of the slab. With this approach, the water is not completely removed from the space. The result is that humidity, mold, and mildew can still be a problem. This system also cannot drain groundwater from under the floor slab.