Minimum requirements; law not to be modified. The provisions of the act shall be held to be the minimum requirements adopted for the protection of health, welfare and safety of the community. Nothing herein contained shall be deemed to invalidate existing ordinances or regulations of any city or organized village or the board of health of any such city or village imposing requirements higher than the minimum requirements laid down in this act relative to light, ventilation, sanitation, fire prevention, egress, occupancy, maintenance and uses for dwellings; nor be deemed to prevent any city or organized village or the board of health of any such city or village from enacting and putting in force from time to time ordinances and regulations imposing requirements higher than the minimum requirements laid down in this act; nor shall anything herein contained be deemed to prevent such cities and organized villages or the board of health of any such city or village from prescribing for the enforcement of such ordinances and regulations, remedies and penalties similar to those prescribed herein. And every such city and organized village or the board of health of any such city or village is empowered to enact such ordinances and regulations and to prescribe for their enforcement. No ordinance, regulation, ruling or decision of any municipal body, officer of authority of the board of health of any such city or village shall repeal, amend, modify or dispense with any of the said minimum requirements laid down in this act; except that, in order that the provisions of this act may be reasonably applied, public health and safety secured, and substantial justice done in instances where practical difficulties are encountered or unnecessary and unreasonable hardship result from the application of the strict letter of the law, the decision of a board of appeals, as hereinafter provided and regulated shall be considered as the reasonable application of the intent of this act.