Conn. Agencies Regs. § 29-349-160
Magazines of this category shall be of masonry construction or of wood or metal construction, or a combination of these types, and shall be bullet-resistant. Thickness of masonry units shall not be less than 8 inches. Hollow masonry units used in construction shall have all hollow spaces filled with weak concrete or well tamped sand. Wood constructed walls shall be constructed of 1-inch minimum thickness tongue and grooved hardwood lumber, shall have at least a six inch space between interior and exterior sheathing, and the space between sheathing shall be filled with well tamped sand. Metal wall construction shall be lined with a brick at least four inches in thickness or shall have at least a six inch sand fill between interior and exterior walls, or may be constructed of 3/8 inch thick steel plate walls with 2-5/8 inch thick hardwood lining or equivalent construction approved by the State Fire Marshal. Interior walls shall be constructed of or covered with non-sparking material.
Conn. Agencies Regs. § 29-349-160