What Is A French Drain

You could be forgiven for thinking we are back in the days of Camelot, when medieval castles had creaking drawbridges that they would raise and lower over a moat. The moat was in fact a trench filled with water that was built around the entire castle perimeter to disallow entry by undesirables. It worked like a charm and such a low-tech security system would be employed today if we all had plenty of land and had to keep dragons and invaders away.

These days, the moat is called a French drain, but with a few differences. Primarily, it is a drain with no piping system; it is simply a channel bedded with gravel or stone, that collects water that may run-off from your neighbor's property or from the road if it is higher than your allotment.

Excessive moisture is usually a nuisance, but even more so when the moisture originates from outside of your own boundaries. You cannot always take action to prevent the water from ending up in your yard, so a French drain is how you deal with it.

DIY? Or call the pros in?

If you are handy with a shovel and your back isn't likely to suffer too greatly after a few hours of digging, you can probably attempt to build your own French drain. It is always nice, however, if you can watch someone else do your bidding and offer them occasional refreshments. Otherwise, you can employ a contractor to do the work for you; naturally, at a cost.

How to do it yourself:

    1. You will need to find a location on your allotment to where the excess water can be diverted. The perfect spot for your French drain is one that is away from high use areas and it should preferably have sandy soil to allow for optimum drainage.

    2. Check for the presence of underground cabling. If there is no signage present in the vicinity, contact your utilities companies to enquire.

    3. Find a point along the slope on your property where you will best be able to dig. If you are renting a trench digger, make sure you can access the area with it. Plot out the grading to act as a guide, before you start digging. Unless there is a slope on your side of the boundary, the water won't be able to move downwards to the drainage point. French drains should consist of a minimum 1% grade.

    4. Plan for the size your French drain will need to be before you dig. If its not going to be big enough, the whole exercise will be pointless. A width of approximately 5 to 6 inches and around 9 to 12 inches deep ought to be sufficient.

    5. Begin digging the trench horizontally all across the slope. One end should aim towards the drainage point and if you cannot make it travel far enough to reach it, then you will need to dig a second trench towards it, and connect it with the first.

    6. Line the French drain with landscaping fabric to prevent dirt from getting into the gravel you will add later. In order for the drain to work efficiently, the porosity of the gravel should be maintained.

    7. Using coarse gravel, make a layer over the fabric then fold the ends of the fabric over the top of the gravel.

Keep it safe

For the purpose of good looks and safety (so that no one falls in), add a layer of coarse sand over the top of your French drain and add some light dirt to blend with the rest of the yard.

Et voila , a French drain you can be proud of, that will serve your castle well!

See Also:

Installing Drainage Systems