A fire insurance policy shall contain a provision as follows: “Unless otherwise provided in writing added hereto this company shall not be liable for loss occurring:
“(1) While the hazard is increased by any means within the control or knowledge of the insured; or
“(2) While a described building, whether intended for occupancy by owner or tenant, is vacated or unoccupied beyond a period of 60 consecutive days; or
“(3) As a result of explosion or riot, unless fire ensues, and in that event for loss by fire only.”