(a) Front yard.
(1) There shall be a front yard having a depth of not less than 25 feet except as required for arterial and collector streets in Article 29 of this Title.
(2) Where a lot has double frontage or is a corner lot, a front yard shall be provided on both streets.
(3) Where a principal or accessory building existing as of the effective date of this Title, encroaches upon the required 25 foot front yard, and where the building is on a single lot of record, as defined in the definitions section of this Title, established prior to the effective date of said Title, and having an area of not more than 7,500 square feet, an addition to said building shall be permitted, provided the addition does not encroach further into the required front yard than the furthest projection of said building, and providing that said addition represents not more than 50% of the lot coverage of the existing building.