Drainage cloth is important part of French drain

Posted1/4/2019 6:00 AM

Q. When I bought my house, the home inspector advised installing a "French drain" to prevent flooding in the basement. He described how this should be done, but the part I didn't understand was lining the trench with cloth. Could you please explain the function of a "French drain" and how it should be installed?

A. French drains are underground drainage systems intended to redirect the flow of groundwater. Typically, they are installed to prevent flooding, soil erosion, excessive moisture conditions and other water-related problems. The basic idea behind a French drain is to provide a path of least resistance, to channel the flow of groundwater to a downhill location where it will not cause damage to structures.

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Construction of a French drain is fairly simple, although somewhat labor intensive. Basically, a French drain consists of a trench filled with rocks. Groundwater flows into the trench because the spaces between the rocks provide an unrestricted pathway, as compared with compacted soil. A perforated drain pipe at the bottom of the trench conveys the water to a location well away from buildings on the property.

To ensure that a French drain will continue to function for many years, it is essential to prevent sand and soil from filling the spaces between the rocks. Gradual intrusion of sediment can eventually impact a French drain so that it is no longer functional. This is the reason for lining the trench with a cloth membrane.

If you build a French drain yourself, remember to use a cloth membrane specifically made for that purpose. Drainage cloth is manufactured to withstand burial without decomposing. Other types of material will have limited longevity.

As a final precaution, have your drainage problems professionally evaluated by a licensed geotechnical engineer before you install a French drain. Drainage conditions, especially on hillside properties, can defy simple analysis, owing to the variables that can affect underground water movement. The money you spend on a professional opinion can ensure your French drain performs effectively once it is in place.


Q. We are trying to add a gas log lighter to our fireplace but have run into a problem. The fireplace already has a gas pipe and valve, but when we installed a new log lighter, the burner would not light. Our home inspector said something is wrong with the gas piping, possibly inside the wall. We're wondering how we can fix this at minimal expense. What do you suggest?

A. There could be a problem with the gas piping in the wall, as suggested by your home inspector, but it is also possible that the pipe is no longer connected to the fuel supply or that there is a closed or faulty gas valve. Rather that guessing the cause or looking for an economical solution, have the problem evaluated and repaired by a licensed plumber. Otherwise, your whole house could become a fireplace.

• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

© 2019, Action Coast Publishing

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