The Ontario Building Code | Horizontal Service Space Access
3.6.4.5. Horizontal service Space Access
(1) A horizontal service space, consisting of ceiling and duct spaces, that is more than 1 200 mm high and 600 mm wide shall have inspection doors not less than 300 mm in both horizontal and vertical dimensions placed so that the entire interior of the duct or space can be viewed.
In Plain Language
A horizontal service space made up of ceiling and duct areas taller than 1,200 mm and wider than 600 mm needs inspection doors at least 300 mm square, spaced so the entire interior can be reached and examined.
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.