No land or building or part thereof erected or altered in its use or structure shall be used until the building official shall have issued a certificate of occupancy stating that such land, building or part thereof and the proposed use thereof is found to be in conformity with this chapter. Within three days after notification that a building or premises or part thereof is ready for occupancy or use, it shall be the duty of the building official to make a final inspection thereof and to issue a certificate of occupancy if the land, building or part thereof and the proposed use thereof is found to conform with this chapter. If issuance of such certificate is refused, the building official shall state such refusal in writing with the reason. A temporary certificate of occupancy may be issued by the building official for a period not exceeding six months during alterations or partial occupancy of a building pending its completion, provided that such temporary certificate may require such conditions and safeguards as will protect the safety of the occupants and the public.