In their interpretation and application, the provisions of this chapter shall be held to be the minimum requirements, adopted for the promotion of the public health, safety, morals, comfort, prosperity and general welfare. It is not intended by this chapter to repeal, abrogate, annul or in any way impair or interfere with any existing provisions of law or ordinance or with any rules, regulations or permits previously adopted or issued or which shall be adopted or issued pursuant to law relating to the use of buildings or premises; provided, however, that where this chapter imposes a greater restriction upon the use of buildings or premises or upon heights of buildings, or requires larger yards, courts or other open spaces than are imposed or required by such existing provision of law or ordinance or by such rules or regulations or permits, the provision of this chapter shall control.