Subsoil Drainage ~ Building Regulation C2 requires that subsoil
drainage shall be provided if it is needed to avoid:-
a) the passage of ground moisture into the interior of the
building or
b) damage to the fabric of the building.
Subsoil drainage can also be used to improve the stability of the
ground, lower the humidity of the site and enhance its horticultural
properties. Subsoil drains consist of porous or perforated pipes
laid dry jointed in a rubble filled trench. Porous pipes allow the
subsoil water to pass through the body of the pipe whereas
perforated pipes which have a series of holes in the lower half
allow the subsoil water to rise into the pipe. This form of ground
water control is only economic up to a depth of 1„500, if the
water table needs to be lowered to a greater depth other
methods of ground water control should be considered (see pages
307 to 311).
The water collected by a subsoil drainage system has to be
conveyed to a suitable outfall such as a river, lake or surface
water drain or sewer. In all cases permission to discharge the
subsoil water will be required from the authority or owner and in
the case of streams, rivers and lakes, bank protection at the
outfall may be required to prevent erosion (see page 748).
Subsoil Drainage