French drains and rear wall drainage
A French drain is a drain with no pipe. The water collects in a gravel
or stone filled channel that starts from the surface of just below it.
The advantage of a French drain is that is easy to construct and with
the use of modern ground fabrics very efficiant. With the use of a little budgeting, it is very easy to afford this project within your personal budget
The photos we show in this article show a French drain being constructed
behind a low retaining wall. First you need to dig a trench behind the
wall about 15cm wide and as deep as required with a fall off 1 in 100
so that the water flows. Next the trench should be linned with ground
sheeting which is avaiable at most builders merchants. This sheeting
allows water to pass through but not the soli particles such as silt
and clay that often block drains after a number of years.
Fill the trench inside the sheeting with a clean stone, 20mm is ideal
or clean broken bricks. The trench can be filled to the surface or as
shown in our photo it has been filled to about 10cm below the surface
and the sheeting wrapped around it. Then backfilled with topsoil over
The drain will needed to end in a soak away. This is a large cube shaped
hole linned with ground sheeting and filled with clean gravel or clean
rubble. The idea is that when the drain is working the water runs into
the soakaway and over a few hours soaks into the surounding ground soil.
For this reason it is best to pick an area of land that drains freely