The Ontario Building Code | Furring
9.27.5.3. Furring
(1) Except as permitted in Sentences 9.27.5.1.(5) and (6), furring for the attachment of cladding shall be not less than 19 mm by 38 mm lumber when applied over sheathing.
(2) When applied without sheathing, furring referred to in Sentence (1) shall be not less than,
(a) 19 mm by 64 mm lumber on supports spaced not more than 406 mm o.c., or
(b) 19 mm by 89 mm on supports spaced not more than 610 mm o.c.
(3) Furring referred to in Sentence (1) shall be,
(a) securely fastened to the framing, and
(b) spaced not more than 610 mm o.c.
In Plain Language
Furring, strips added to create an air space behind the cladding, must meet the requirements set out in this article where used.
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.