The Ontario Building Code | Sway Forces in Assembly Occupancies
4.1.5.10. Sway Forces in Assembly Occupancies
(1) The floor assembly and other structural elements that support fixed seats in any building used for assembly occupancies accommodating large numbers of people at one time, such as grandstands, stadia and theatrebalconies, shall be designed to resist a horizontal force equal to not less than 0.3 kN for each metre length of seats acting parallel to each row of seats, and not less then 0.15 kN for each metre length of seats acting at right angles to each row of seats, based on the assumption that these forces are acting independently of each other.
In Plain Language
Floor assemblies and other structural elements supporting fixed seating in assembly buildings must be designed to resist sway forces, the side-to-side forces a crowd can generate by moving together rhythmically.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.