It shall be unlawful for any person to encumber or obstruct any street, alley or sidewalk with building or other like materials without having obtained a written permit from the mayor or city council, except in cases of urgent necessity and for a short time only, or to allow any obstruction that he may by himself or by agent have made, to continue in any case longer than may be necessary in the diligent erection of such building or the prompt execution of the work. (Ord. 11, 2-6-1917)