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4. NBCC 2015 and NBCC 2020 CpCg Values

NBCC 2015 and NBCC 2020 CpCg Values

The SkyCiv Load Generator uses digitized values of the following figures in calculating the $$C_{p} C_{g}$$ in calculating the design wind pressures for structural components and cladding:

• Figure 4.1.7.6.-B – External peak values of $$C_{p} C_{g}$$ on individual walls for the design of cladding and secondary structural members;
• Figure 4.1.7.6.-C – External peak values of $$C_{p} C_{g}$$ on roofs with a slope of 7° or less for the design of structural components and cladding;
• Figure 4.1.7.6.-E – External peak values of $$C_{p} C_{g}$$ on single-span gabled and hipped roofs with a slope greater than 7° for the design of structural components and cladding; and
• Figure 4.1.7.6.-G – External peak values of $$C_{p} C_{g}$$ on monoslope roofs for the design of structural components and cladding.

The process is done by using Engauge Digitizer, as the exact values in the graphs are not explicitly shown or stated in the code reference. With this, for transparency, the following data are being used in the Load Generator – Wind Load Calculations using NBCC 2015 and 2020. The adopted values are rounded to the nearest tenths (higher magnitude). Values in between known points are interpolated linearly using log-scale for the area axis.

Figure 4.1.7.6.-B – $$C_{p} C_{g}$$ on individual walls for the design of cladding and secondary structural members

Zone Area, sq.m. $$C_{p}C_{g}$$
$$e^{-}$$ ≤ 1 -2.1
≥ 50 -1.5
$$w^{-}$$ ≤ 1 -1.8
≥ 50 -1.5
$$e^{+}$$ and $$w^{+}$$ ≤ 1 1.8
≥ 50 1.3

Figure 4.1.7.6.-C – $$C_{p} C_{g}$$ on roofs with a slope of 7° or less for the design of structural components and cladding

Zone Area, sq.m. $$C_{p} C_{g}$$
$$s^{-}$$ ≤ 7.128 -2.5
≥ 10 -2.0
$$r^{-}$$ ≤ 1 -1.8
≥ 10 -1.5
$$c^{-}$$ ≤ 1 -5.4
≥ 10 -2.0
$$oc^{-}$$ ≤ 1 -5.4
≥ 10 -1.5
$$os^{-}$$ ≤ 1 -3.2
10 -3.0
≥ 50 -2.0
$$or^{-}$$ ≤ 1 -3.2
10 -3.0
≥ 50 -2.0
$$s^{+}$$, $$r^{+}$$, and $$c^{+}$$ ≤ 1 0.5
≥ 10 0.33

Figure 4.1.7.6.-E – $$C_{p} C_{g}$$ on roofs with a slope of $$7° \lt \alpha \leq 27°$$

Zone Area, sq.m. $$C_{p} C_{g}$$
$$s^{-}$$ ≤ 2.2 -3.6
≥ 10 -2.6
$$r^{-}$$ ≤ 0.9 -2.5
≥ 8.9 -2.05
$$c^{-}$$ ≤ 1.1 -5.0
≥ 10.8 -4.0
$$oc^{-}$$ ≤ 1.1 -7.0
≥ 11.1 -4.7
$$os^{-}$$ ≤ 1 -4.1
≥ 10 -4.1
$$or^{-}$$ ≤ 1 -1.6
≥ 10 -1.6
$$s^{+}$$, $$r^{+}$$, and $$c^{+}$$ ≤ 1.2 0.8
≥ 7.94 0.5

Figure 4.1.7.6.-E – $$C_{p} C_{g}$$ on roofs with a slope of $$27° \lt \alpha \leq 45°$$

Zone Area, sq.m. $$C_{p} C_{g}$$
$$s^{-}$$ ≤ 0.75 -2.1
≥ 7.95 -1.9
$$r^{-}$$ ≤ 1.26 -1.8
≥ 12.6 -1.5
$$c^{-}$$ ≤ 0.75 -2.1
≥ 7.95 -1.9
$$oc^{-}$$ ≤ 1 -3.8
≥ 10.9 -3.3
$$os^{-}$$ ≤ 1 -3.8
≥ 10.9 -3.3
$$or^{-}$$ ≤ 1 -1.8
≥ 10 -1.8
$$s^{+}$$, $$r^{+}$$, and $$c^{+}$$ ≤ 0.8 1.6
≥ 7 1.5

Figure 4.1.7.6.-G – $$C_{p} C_{g}$$ on roofs with a slope of $$3° \lt \alpha \leq 10°$$ Monoslope Roof

Zone Area, sq.m. $$C_{p} C_{g}$$
$$s^{-}$$ ≤ 2 -2.5
≥ 11 -2.4
$$r^{-}$$ ≤ 1 -2.0
≥ 10.9 -2.0
$$c^{-}$$ ≤ 1.2 -3.4
≥ 11 -2.4
s’ ≤ 1.2 -3.0
≥ 12.3 -2.8
c’ ≤ 0.9 -5.0
≥ 11 -3.0
$$s^{+}$$, $$r^{+}$$, and $$c^{+}$$ ≤ 1.29 -0.6
≥ 12.3 -0.3

Figure 4.1.7.6.-G – $$C_{p} C_{g}$$ on roofs with a slope of $$10° \lt \alpha \leq 30°$$ Monoslope Roof

Zone Area, sq.m. $$C_{p} C_{g}$$
$$s^{-}$$ ≤ 0.83 -3,0
≥ 8.75 -2.2
$$r^{-}$$ ≤ 0.92 -2.6
≥ 11 -1.95
c’ ≤ 0.75 -5.5
≥ 7.5 -2.7
$$s^{+}$$, $$r^{+}$$, and $$c^{+}$$ ≤ 1 0.9
≥ 8 0.5

References:

• Mark Mitchell, Baurzhan Muftakhidinov and Tobias Winchen et al, “Engauge Digitizer Software.” Webpage: http://markummitchell.github.io/engauge-digitizer, Last Accessed: July 12, 2024
• National Research Council of Canada. (2015). National Building Code of Canada, 2015. National Research Council of Canada.