Section 11. Officers in charge of a state department, county commissioners, city councils and selectmen shall, at the expense of the commonwealth, county, city or town, respectively, provide and maintain fireproof rooms, safes or vaults for the safe keeping of the public records of their department, county, city or town, other than the records in the custody of teachers of the public schools, and shall furnish such rooms with fittings of non-combustible materials only.