straighten

Roof Snow Load

(NBC 2025)
v1.0.0
File:
Project:
Designer:
Date:

Climatic Data

Source
Region
Location
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Ground snow load
Ss:
Rain Load
Sr:
Winter Average
Temperature, Tws:
°C
Wind speed, Vws:
m/s

Factors

Importance Factor, Is:
Basic Roof Factor, Cb:
info
If Cb left blank, provide the dimensions in the roof geometry to compute Cb
Wind Factor, Cw:
info
If Cw left blank, Cw will be computed.
Accumulation Factor, Ca:
info
If Ca left blank, Ca will be computed assuming gable roof.
Thermal Factor, CT:
Average indoor temperature, Tin:
°C
Roof Thermal Transmittance, Uroof:
W/(m2K)
info
Provide Ct or Tin and Uroof.
Roof Geometry
Pitch:
/12
Slippery:
Roof Plan dimensions
Dimensions used to calculated Cb if Cb left empty.
Longer dimension, l:
m
Shorter dimension, w:
m
snow gable figure

Specified Snow Load

[4.1.6.2]
S = Is[Ss(CbCwCsCa)+Sr]

Factors

User input values:
Ss = 1 kPa
Sr = 1 kPa
Importance Factors:
ULS: Is = 0.8
SLS: Is = 0.9
Cb = 0.8 (based on input Cb
Roof slope = 0 degrees
Slope Factor
For non-slippery roof:
Slope <= 30 degrees: Cs = 1
[Table A-4.1.6.9]

Snow on Gable Roofs

Load Case I

Same load on both upwind and downwind sides.
ULS:
Cw = 1
Ca = 1

S = 1.44 kPa ( 30.1 psf )

SLS:
Cw = 1
Ca = 1
S = 1.62 kPa ( 33.8 psf )

Load Case II

Load Case II does not apply to gable roofs with slopes of 15 degrees or less.

This information must be read or used in conjunction with Part 4 of the NBC 2025. In the event of discrepancies, Part 4 of the NBC 2025 shall govern.

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