There are more than 12,000 houses in the North Shore community of Northbrook and almost every one of them has a basement.
Because Northbrook boomed after World War II like most suburbs in the United States, a lot of those houses are starting to show their age, especially considering that more than two-thirds of them were built between 1950 and 1980. When houses age, things begin to go wrong and one thing that is a pretty common occurrence is a wet basement.
There are a number of extremely effective and permanent ways to stop seepage in homes in Northbrook and elsewhere but one of the most effective is to install drain tile to alleviate pressure and carry off ground water either inside or outside the foundation.
“Drain tile” can be a confusing term to homeowners. The “drain” part makes sense but what do you mean by “tile?”
I’ll freely admit that “drain tile” is a term that has lingered from the old days and has become a piece of jargon for the basement waterproofing industry. When subsoil drainage systems were first developed (by a man named French, which explains another confusing term, “French drain”) they used pieces of terra cotta roofing tile, set one on top of another, as the conduit for drainage.
Since then, drain tile has evolved from roofing tile to terra cotta pipe to the modern standard of plastic pipe, but the old name has remained.
Whether installed on the interior or exterior, the basics of drain tile are the same. Perforated pipe is installed next to the foundation footings, enclosed in a bed of washed gravel and connected to a sump basin. Underground pressure forces water into the pipe and the water flows to the sump basin where a sump pump discharges it from the house.
The choice between interior and exterior drain tile is typically based on the nature of the seepage problem the home is experiencing. If water is seeping into the basement through cracks in the floor or through the cove joint between wall and floor, interior drain tile is called for. If seepage is coming through the wall because of deteriorated mortar joints or porous masonry units or concrete, then exterior drain tile is recommended.
Installing interior drain tile begins with removing a strip of the basement floor around the perimeter and digging a trench the same width down to the bottom of the footings. Several inches of washed gravel are poured and leveled in the trench and then flexible, corrugated, perforated pipe, wrapped in a sock of filtration fabric is laid on top. The pipe is connected at both ends (for a full-perimeter system) to the sump pit, then another layer of gravel is added and the cement floor is replaced.
When hydrostatic pressure under the foundation pushed water toward the floor it goes into the pipe instead and is carried off to the sump pump for discharge.
An exterior drain tile installation is often done as an adjunct to an exterior waterproofing membrane that seals the wall against water penetration but can also be done on its own. The excavation that has been dug for the membrane to be installed is lined at the bottom with washed gravel, then perforated, rigid PVC pipe, which better withstands exterior pressures and soil exposures, is laid in and connected to a sump basin. More washed gravel goes on top and the excavation is backfilled.
When exterior pressure would ordinarily push water through the wall it instead forces water into the drain tile piping where it is transported to a sump pump.
Regardless of whether the recommended site for drain tile is on the interior or exterior, a Northbrook homeowner in search of a dry basement will need the services of an experienced basement waterproofing contractor. At U.S. Waterproofing, we have installed miles of drain tile on both sides of the foundation wall for thousands of the more than 300,000 satisfied customers we have served since 1957. So, why not ask for our free advice?
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