The Ontario Building Code | Top Plates
9.23.5.4. Top Plates
(1) Top plates in walls shall not be notched, drilled or otherwise weakened to reduce the undamaged width to less than 50 mm unless the weakened plates are suitably reinforced.
In Plain Language
Top plates have specific limits on drilling and notching set out in this article, since this member ties the tops of studs together and often carries floor or roof loads.
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.