Fire separation or firewall: 1 h fire separation (Article 9.10.11.2.), or a 2 h firewall; sound transmission class 50 for the separating assembly (or ASTC 47 with the flanking rules).
A party wall on a property line is a firewall (Article 9.10.11.1.), but a residential party wall may be a fire separation with a fire-resistance rating of not less than 1 h where it separates two dwelling units and no dwelling unit is above another (Article 9.10.11.2.).
The 1 h wall must give continuous protection from the top of the footings to the underside of the roof deck, and any space between the top of the wall and the roof deck must be tightly filled with mineral wool or noncombustible material (Article 9.10.11.2.).
Firewall built to Part 3 (Article 9.10.11.3.): fire-resistance rating not less than 2 h and noncombustible construction (Article 3.1.10.2.(2)), provided by masonry or concrete, except that a firewall rated 2 h or less can be another assembly if it meets the conditions of Article 3.1.10.2.(4). It extends from the ground through all storeys (Article 3.1.10.3.), rises as a parapet not less than 150 mm above the roof for a 2 h rating (Article 3.1.10.4.), and openings are limited to 25 percent of its length in a storey (Article 3.1.10.5.).
Sound: a dwelling unit must be separated from every other space where noise may be generated by a separating assembly and adjoining construction giving an apparent sound transmission class (ASTC) of 47 or more, or by a separating assembly of STC 50 or more with flanking construction that meets Article 9.11.1.4. (Article 9.11.1.1.(1)).
Compliance is shown by tested ratings or by an assembly conforming to Table 1 or 2 of Supplementary Standard SB-3, Fire and Sound Resistance Tables (Article 9.11.1.3.).
Limits: Part 9 housing and small buildings (a building of up to 3 storeys and 600 m2 in area). Larger buildings, other occupancies, sprinklered high buildings, wall assemblies and their listings, penetrations and closures are outside this tool; Part 3 and the designer apply. Your municipality and the designer of record confirm the assembly.
Source: 2024 Ontario Building Code (O. Reg. 163/24), Division B, Articles 9.10.8.1., 9.10.9.15., 9.10.9.16., 9.10.9.18., 9.10.11.1. to 9.10.11.4., 9.11.1.1. and 9.11.1.3., and Article 3.1.10.2. to 3.1.10.5.
Tool: https://timberrframing.com/firewall-and-party-wall-fire-rating-checker/
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Preliminary planning only; the designer or engineer of record and the building permit set govern.