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Today’s housing code requires an exterior drainage system – drain tile or French drain. Below is a summary of a proper installation. But not all are done the same, with some builders omitting stone, some using fabric filters, and all installing various forms of plastic pipe.
No matter the method, we have found all exterior drainage fails over time and needs to be replaced or supplemented.
French drains will typically be installed after the home’s foundation is laid. A layer of gravel is laid down around the foundation’s perimeter, with the French drain piping laid on top. Gravel is then laid on top of the pipe. Sometimes, filter fabric is then laid on top of the pipe to keep finer sediment from the earth from passing through the gravel. Foundation soil is then backfilled on top of the system, and the gap around the foundation is filled in.
This old-fashioned waterproofing system, like many interior drainage systems, is very limited and tends to collect sediment and clog frequently. These systems have been known to go ten years without a problem, but they unfortunately provide a limited solution that will eventually need to be serviced. As the filter fabric that was designed to keep small sediments out of the pipe does its job, the fabric itself will eventually be overwhelmed with material and will clog.
The weakness of a filter is that once buried (about eight-feet deep) there’s no way to change it – think air filter or oil filter – they need to be changed when they clog.
We have found exterior footing drains packed with dirt, filled with tree roots, or even non-existent. Interior methods are far more reliable, and the best drain tile and French drain systems sit out of the mud and are easily accessed.
If a French drain or drain tile basement waterproofing system has no filter fabric installed, mud, sand, and sediments will have no barrier when they make their way through the gravel to clog the pipe. Homeowners will eventually find that they need alternate ways to deal with the problems as these clogged systems fail.
Eventually, an exterior French drain will need to be serviced. When it does, the entire perimeter of the foundation will need to be excavated. Any landscaping located around the edges of the house- gardens, steps, shrubbery, porches, walkways, and any other landscaping must be removed so that the foundation may be excavated.
The failed exterior French Drain or drain tile system will then be replaced with an identical one. After this, loose soil will be filled back in and will hold even more foundation water. After a year, the earth against your foundation will settle and need to be regraded once more. In a decade, or perhaps longer, the whole process must be repeated again.
Often, houses that have a flooded basement also have a failed exterior French drain system. Contact us for a free consultation on your specific drainage situation.