Certain Work Prohibited

No apartment owner shall do any work which would jeopardize the soundness or safety of the property, reduce the value thereof, or impair any easement or hereditament, nor may any apartment owner add any material structure or excavate any additional basement or cellar, without in every such case the unanimous consent of all the other apartment owners being first obtained; provided, that additions to or alterations of an apartment made within such apartment or within a limited common element appurtenant to and for the exclusive use of the apartment shall require approval only by the Board of Directors of the association of apartment owners and such percentage, number, or group of apartment owners as may be required by the declaration or bylaws.