The Ontario Building Code | Fastening to Lath
9.27.7.5. Fastening to Lath
(1) When lath is used with double-course application (see Sentence 9.27.5.1.(5)), it shall be spaced according to the exposure and securely fastened to the framing.
(2) The butts of the under-course of the application referred to in Sentence (1) shall rest on the top edge of the lath.
(3) The outer course of the application referred to in Sentence (1) shall be fastened to the lath with nails of sufficient length to penetrate through the lath.
(4) The butts of the shingles or shakes shall be so located that they project not less than 12 mm below the bottom edge of the lath referred to in Sentence (1).
(5) If wood lath is not used, the butts of the under-course shingles or shakes of the application referred to in Sentence (1) shall be located 12 mm above the butts of the outer course.
In Plain Language
This clause covers how double-course wood shingles or shakes attach to lath: spacing depends on weather exposure, the under-course butts rest on the lath's top edge, the outer course is nailed through the lath, and there are minimum shingle overhang and offset requirements depending on whether wood lath is 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.