Leaky Basement Walls
Leaks and squeaks; they’re two of a contractors worst nightmares. They can also drive most homeowners bonkers. Fortunately, with patience and persistence, the source of most leaks and squeaks can be located and repaired. However, trying to locate the leak or squeak can often be more painstaking and time consuming than the actual repair.
Although a squeaking floor can be quite irritating, it is insignificant compared to the damage that an undetected leak can cause. Water is by far the greatest threat to any home. Thus, considering pounding that most people have been taking by El Nino, we’ll concentrate on leaks and leave squeaks for another day.
A basement is a prime location for leaks. The fact that a basement is, by design, below grade (ground level) makes it especially susceptible to leaks. This is regardless its construction. All types of basement construction are subject to leaks whether they are constructed of block, brick or poured-in-place concrete.
Why do basements leak? For many reasons. Surface run-off due to poor grading, lack of, or defective, gutters and downspouts, blocked drainage at the base of a home’s exterior walls and a defective or missing footing drainage system are a few of the most common causes.
Enough can’t be said for the importance of proper grading. The soil surrounding the home should drain AWAY from the foundation. The grade doesn’t need to be extreme, just enough to keep the water running in the right direction. This should be done for a minimum distance of three feet from the foundation.
Along with good grading go gutters and downspouts. If your home doesn’t have gutters and downspouts, install them. If they exist and are leaking or clogged with debris, clean and repair them for peak performance. A garden hose with a high-pressure spout along with a high-quality caulking compound is all you’ll generally need.
A good watershed system doesn’t end with gutters and downspouts. Downspouts should discharge into solid drainpipe that will carry the water away from the home into non-erosive material or a municipal storm drain system.
A footing drainage system (French drain) will collect sub surface water and relieve hydrostatic pressure. Hydrostatic pressure is a phenomenon that results from groundwater pressing against foundation walls. This pressure can be so intense that it may pop out the joint mortar between concrete blocks or between the walls and the floor.
The footing drainage system consists of a perforated pipe surrounded by a belt of gravel. The system is located at the base of the footing at the perimeter of the house. Periodically the drainage system will need to be flushed with a garden hose to remove silt and clogs.
Aside from the elements listed above, the key to a dry basement is a sound waterproof membrane at the exterior of the basement walls and floor. There are various waterproofing materials that are used including a built-up asphalt system; single play membranes and other impervious systems. These membranes are typically applied to the exterior surface of the basement walls during the construction process.
Prior to backfilling the area surrounding the basement with soil, the membrane is protected from potential damage with rigid foam, landscape fabric or a combination of the two.
Maintaining proper grading and installing and maintaining gutters, downspouts and a drainage system are reasonably non threatening, inexpensive tasks that can be performed by most homeowners. On the other hand, installing a French drain can be a project best left to a professional. Before attempting to install a French drain, the system should be designed by a soils engineer.
If after paying heed to our suggestions heretofore, the basement continues to leak, there are measures that can be taken on the interior to resolve the problem. Most often, water enters a basement through cracks or mortar joints between concrete blocks.
The first step in repair in the repair process is to chisel the crack wider to create space for patch material. This is best done using a chisel and a small sledgehammer. A continuous flow of water from the crack indicates high ground water or intense hydrostatic pressure. This condition should be relieved before proceeding with the repair.
An effective means of relieving this pressure is by inserting a “bleeder tube” into the crack. This is a temporary drainpipe consisting of iron, copper or rubber. The tube should discharge into a bucket.
Next, with the bleeder tube still in place, fill the crack with hydraulic cement. Use a trowel to pack the material into the crack. While the hydraulic cement hardens, form a stiff hydraulic cement mix into a plug. Pull out the bleeder tube and fore the plug into the hole. Smooth out the plug and hold it in place with the trowel until the cement hardens.
Although most successful waterproofing is done from the exterior, or “source side” of a wall, there are some after-market applications that can be used successfully to combat damp or wet walls. This is especially useful when waterproofing from the exterior is neither possible nor practical.
One such method that has been used primarily for industrial and commercial applications is becoming increasingly popular for residential use. The system is called XYPEX Concrete Waterproofing by Crystallization.
Xypex consists of portland cement, very fine treated silica sand and various active proprietary chemicals. When mixed with water and applied as a cementitious coating, the active chemicals in Xypex cause a catalytic reaction that generates a nonsoluable crystalline formation of dendritic fibers with the pores and capillary tracts of concrete. Thus, the concrete becomes permanently sealed against the penetration of water or liquids from any direction.