If a drain or sewer is within the area covered by that 45 degrees area there is a risk that it could be affected by the load from the foundation and possibly crack.
Os oes draen neu garthffos yn yr ardal sydd o fewn yr ongl honno o 45 gradd, mae perygl y gallai llwyth y sylfaen effeithio arnynt ac y gallent gracio.