The Ontario Building Code | Variation with Tributary Area

4.1.5.8. Variation with Tributary Area

(1) An area used for assembly occupancies designed for a live load of less than 4.8 kPa and roofs designed for the minimum loading specified in Table 4.1.5.3. shall have no reduction for tributary area.

(2) Where a structural member supports a tributary area of a floor or a roof, or a combination of them, that is greater than 80 m² and either used for assembly occupancies designed for a live load of 4.8 kPa or more, or used for storage, manufacturing, retail stores, garages or as a footbridge, the specified live load due to use and occupancy is the load specified in Article 4.1.5.3. multiplied by,

0.5 +

where,

"A" is the tributary area in square metres for this type of use and occupancy.

(3) Where a structural member supports a tributary area of a floor or a roof or a combination of them, that is greater than 20 m² and used for any use or occupancy other than assembly occupancies and those indicated in Sentences (1) and (2), the specified live load due to use and occupancy, is the load specified in Article 4.1.5.3. multiplied by,

0.3 +

where,

"B" is the tributary area in square metres for this type of use and occupancy.

(4) Where the specified live load for a floor is reduced in accordance with Sentence (2) or (3), the structural drawings shall indicate that a live load reduction factor for tributary area has been applied.