It is not intended by this chapter to repeal, abrogate, annul or in any way to impair or interfere with existing provisions of other laws or ordinances (except those specifically repealed by this chapter) nor with any permits previously issued or which shall be issued pursuant to law relating to the use of buildings or premises nor with any private restrictions placed upon property by covenant, deed or other private agreement; provided, however, that where this chapter imposes a greater restriction upon the use of buildings or premises or upon the height of buildings or the percentage of lot coverage, or requires greater lot area, yards or other open spaces than are imposed or required by such ordinances, permits or private restrictions, the provisions of this chapter shall control.