The Ontario Building Code | Lapped Strip Siding
220.127.116.11. Lapped Strip Siding
(1) Plywood applied in horizontal lapped strips shall have not less than a 2 mm gap provided at the butted ends, which shall be caulked.
(2) The horizontal joints of siding described in Sentence (1) shall be lapped not less than 25 mm.
(3) Wedges shall be inserted under all vertical butt joints and at all corners when horizontal lapped plywood is applied without sheathing.