Where additional drainage is required because of the high clay content of the soil surrounding the building, for example, a French drain can provide a very effective and inexpensive solution.
Os oes angen mwy o gyfleusterau draenio am fod y pridd o amgylch yr adeilad yn cynnwys llawer iawn o glai, er enghraifft, gall draen Ffrengig fod yn ateb effeithiol a rhad iawn.