Notwithstanding the provisions of regulation 2 the copyright in a building plan in respect of which the original or a reproduction is lodged for purposes of record at an office of a local authority shall not be infringed by the making of a reproduction of such plan by the person in charge of such office or by any other person acting by or with the authority of such person if the owner of land upon which a building has been erected in accordance with that plan requires copies of the plan or any portion thereof for the purpose of making additions of alterations to such building. *