Mo. Rev. Stat. § 292.090

All scaffolds or structures used in or for the erection, repairing or taking down of any kind of building shall be well and safely supported, and of sufficient width, and so secured as to insure the safety of persons working thereon, or passing under or about the same, against the falling therein, or the falling of such materials or articles as may be used, placed or deposited thereon. All persons engaged in the erection, repairing or taking down of any kind of building shall exercise due caution and care so as to prevent injury or accident to those at work or nearby.