The Ontario Building Code | Attics and Roof Spaces attics and Roof Spaces

(1) ceiling joists or truss bottom chords in residential attic or roof spaces having limited accessibility that precludes the storage of equipment or material shall be designed for a total specified load of not less than 0.35 kPa, where the total specified load is the sum of the specified dead load plus the specified live load of the ceiling.

9.4.3. Deflections