Such bases do not have engineered features (which may include sealed drainage) and may be made from crushed or re-used materials, such as concrete or tarmac.
Nid oes gan seiliau o'r fath nodweddion wedi’u peirianyddu (a all gynnwys draeniad wedi'i selio) a gellir eu gwneud o ddeunyddiau wedi'u malu neu eu hailddefnyddio, fel concrit neu darmac.