The Ontario Building Code | Fire Blocks in Wall Assemblies
220.127.116.11. Fire Blocks in wall Assemblies
(1) Except as permitted by Sentence (2), fire blocks conforming to Article 18.104.22.168. shall be provided to block off concealed spaces within a wall assembly,
(a) at every floor level,
(c) so that the maximum horizontal dimension is not more than 20 m and the maximum vertical dimension is not more than 3 m.
(2) Fire blocksconforming to Sentence (1) are not required provided,
(c) the exposed materials within the wall space, including insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation but not including wiring, piping or similar services, have a flame-spread rating not more than 25 on any exposed surface, or on any surface that would be exposed by cutting through the material in any direction, and fire blocksare installed so that the vertical distance between them is not more than 10 m, or
(d) the insulated wall assembly contains not more than one concealed air space and the horizontal thickness of that air space is not more than 25 mm.