Wind can exert negative and positive pressures on interior walls and partitions, therefore careful attention must be paid to differences in air pressure on opposite sides of the wall. Differences in air pressure may result from: pressure differences between the windward and leeward sides, stack effects due to a difference in air temperature between the exterior and interior, and air pressurization by the mechanical services of the building (NBCC 4.1.7.10.).

The National Building Code of Canada 2015 Structural Commentary (I, 58) suggests an unfactored wind pressure of at least 0.25 kPa, or a value of 0.50 kPa in situations where large openings exist in the exterior envelope and there is a potential for exterior wind pressures to be transmitted to interior walls and partitions.

Additional consideration should be given to walls adjacent to openings such as windows or doors, since these elements will affect the load paths of the wind force over the walls. This calculator limits openings to a maximum length of 1.2 m, however, masonry partitions containing larger openings can still be used with designs provided by a structural engineer.

If there is uncertainty about the expected wind pressure on the interior partition walls, a structural engineer can be consulted for guidance.

The seismic hazard index (I_EF_aS_a(0.2)) is a standardized representation of the anticipated earthquake hazard for a particular site and building. It is defined as the product of the earthquake importance factor (I_E), the site coefficient (F_a), and the 5% damped spectral response acceleration for a natural period of 0.2 seconds (S_a(0.2)). For the design of masonry partition walls, the seismic hazard index is relevant for calculating the seismic loads (NBCC (4.1.8.18.)) and may trigger prescriptive limits at specific thresholds as prescribed by CSA S304 (Clause 4.5 and 16).

Unreinforced masonry may be used where the seismic hazard index is less than 0.35. Where the seismic hazard index is greater than 0.35 but less than 0.75, unreinforced partition walls may still be used under very restrictive conditions: they must have a mass less than or equal to 200 kg/m² (1.96 kN/m²), have a height not greater than 3 m, and must be laterally supported at the top and bottom. Where the seismic hazard index is greater than 0.35 and those conditions are not met, masonry partitions must be reinforced.

Reinforced masonry partitions must have a minimum total reinforcement ratio of 0.05% of the gross cross-sectional area of the wall (taken perpendicular to the direction of the reinforcement considered) where the seismic hazard index is greater than 0.35 but less than 0.75. Additionally, the maximum spacing of vertical reinforcement in partition walls where the seismic hazard index is less than 0.75 is limited to the lesser of 12 (t + 10) or 2,400 mm. Partition wall designs where seismic hazard index is greater than 0.75 are beyond the scope of this calculator. Masonry partitions can still be used in these cases with designs provided by a structural engineer.

The seismic hazard index is typically indicated within the structural drawings, geotechnical report, or may be determined by a structural engineer.