A private garage (detached), provided that the building shall not provide storage for more than one private passenger automobile for each 1,500 square feet of lot area; however, such detached garage shall not be designed or built to house more than two private passenger automobiles, shall not exceed 400 square feet in total floor space and shall not contain more than two vehicle doors, overhead or otherwise, each of which shall not be larger in width or height than is required for the ingress and egress of a private passenger automobile or for two private passenger vehicles if the two vehicle doors are combined as one door. Such a garage shall not be placed nearer to a side or rear property line than five feet and shall not be within 10 feet of the rearmost portion of the main building or nearer to a side street line than 25 feet. Nothing herein, however, shall prevent the construction of a garage as a structural part of a dwelling, provided that such a garage does not store more than two private passenger automobiles, and provided, further, that the outer walls of the building are used when measuring the front, side and rear yards as required under § 162-142.