How to create a French drain

Installing a French drain is very simple, it involves digging a trench for discrete and efficient drainage of surface water. French drains can be big or small, depending on the amount of water that needs draining and the size of the area where the flooding or surface water will be.

It sounds like a big job, but it really isn’t with the know how and tools to complete the job.

What is a French drain?

A French drain is a trench filled with gravel or rocks, containing a perforated pipe that redirects surface water and groundwater away from an area.

French drains are primarily used to prevent ground and surface water from penetrating or damaging building foundations and as an alternative to open ditches or storm sewers for streets and highways. French drains are also used behind retaining walls to relieve ground water pressure.

What you need to get started

To get your project on its way, you will need a simple list of tools and materials.

The tools you will require are a shovel, or digger for bigger projects, and a wheelbarrow. The materials you need are a water-permeable landscape fabric, perforated plastic piping, making sure the pipe that you choose is the right size for the amount of water it needs to carry, and 10-20mm aggregate.

Our step by step guide

Step 1:

Firstly you need to dig a trench.

When digging the trench, make sure it is wider than the pipe you wish to use and that it has a gradient to it. The fall will help the rainwater to naturally drain away.

Step 2:

Next step is to add some of the landscaping fabric to the bottom of the trench and up both sides. Keep enough fabric on either side to lay over the pipe once fitted.

Once that is done, you can put in a layer of your 10-20mm aggregate on top of the fabric. Fill the trench roughly one third of the way up. 

Step 3:

Now you’re ready to place the pipe into the trench.

Lay your chosen pipe with the perforated holes face down. If you lay it any other way, the water won’t be able to escape the pipe until it is too full!

Step 4:

Next step, fill with the rest of the aggregate!

If you wish to make your french drain invisible, make sure the aggregate is only filled 10mm lower ground level, this will give you space to hide it.

Step 5:

Cover the whole of the top of the French drain in the landscaping fabric.

The fabric that was sticking out the edges of the trench should now be wrapped over the aggregate and pipe. Make sure there is no gap between the edges of the fabric., as this will stop any debris from entering the drain and clogging up the system.

Step 6:

For those of you who are wanting to hide your drain, you can now place your grass/slabs etc back on top of the drain. Personally, I think they can make a nice feature in a garden so would choose to decorate with decorative aggregates and rocks!

And that’s it, you’re all done. As easy as that!