Snow load

From the snow load on the ground to the load on the roof: shape coefficients, the undrifted and drifted arrangements for mono-pitch, pitched and multi-span roofs, the drift against a taller building — to EN 1991-1-3.

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INPUTEN 1991-1-3 · kN · m · °

1 · Site Ground snow load s_k [kN/m²] from the national snow map Topography (Table 5.1)

C_t

Design situation

2 · Roof widths are in plan Roof type

Pitch α₁ [°] Pitch α₂ [°]

Width b₁ [m] Width b₂ [m]

Snow prevented from sliding off fence, parapet

3 · Local effects optional · 0 = none

Obstruction height h [m] §6.2 Snowguard to ridge b [m] §6.4

Results update as you type. The coefficients are the code's recommended values — confirm them, and s_k, against your National Annex.

LOAD ARRANGEMENTS · s [kN/m²] on plan

LARGEST s0.800 kN/m²

UNDRIFTED s0.800 kN/m²

LARGEST TOTAL PER METRE9.60 kN/m

C_e · C_t · s_k1.000 kN/m²

LOAD ARRANGEMENTS · every one has to be considered
Case	Zone	x m	μ	s kN/m² (plan)	s·cos α kN/m² (surface)	Total kN/m
Case (i) · undrifted	Slope 1	0.00–8.00	0.800	0.800	0.725	6.40
	Slope 2	8.00–14.00	0.533	0.533	0.409	3.20
Case (ii) · drifted	Slope 1	0.00–8.00	0.400	0.400	0.363	3.20
	Slope 2	8.00–14.00	0.533	0.533	0.409	3.20
Case (iii) · drifted	Slope 1	0.00–8.00	0.800	0.800	0.725	6.40
	Slope 2	8.00–14.00	0.267	0.267	0.204	1.60

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HOW IT'S CALCULATED · WITH YOUR NUMBERS

Step by step, with your numbers

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Equilibrium████ ██ ███████ · ██████ = ██.██
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Reactions████ ██ ███████ · ██████ = ██.██
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Shear force████ ██ ███████ · ██████ = ██.██
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Bending moment████ ██ ███████ · ██████ = ██.██
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Deflection████ ██ ███████ · ██████ = ██.██
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Stress████ ██ ███████ · ██████ = ██.██

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Reference: EN 1991-1-3:2003 §5.2 (snow load on roofs), §5.3 (roof shape coefficients) and §6 (local effects). Recommended values; the National Annex and its snow map govern.

ASSUMPTIONS & LIMITS

EN 1991-1-3:2003 §5.2 and §5.3 with the recommended values: C_e from Table 5.1, shape coefficients from Table 5.2, 0.8 ≤ μ_w ≤ 4, 5 m ≤ l_s ≤ 15 m. A National Annex may change any of them — check yours.
s_k is the characteristic ground snow load for the site, entered by the user from the national snow map. It is not looked up or adjusted for altitude here.
Loads are per square metre of plan (horizontal projection); s·cos α is the load per square metre of roof surface.
Table 5.2 assumes snow can slide off the roof. With a snow fence, an obstruction or a parapet at the lower edge μ_1 is not reduced below 0.8.
Every load arrangement shown has to be considered; the governing one depends on the member being designed.
Not covered: cylindrical roofs (§5.3.5), exceptional snow drifts (Annex B), snow overhanging the roof edge (§6.3), rain on snow, ponding and melting-and-refreezing effects.
For a roof abutting a taller building the lower roof is flat, and the sliding coefficient μ_s is entered by the user (0 when the upper roof is no steeper than 15°).

DISCLAIMER · For education and preliminary sizing only. Results must be reviewed by a qualified engineer before use in design.

BEYOND THE CODE SHAPES

Complex roofs, drifting around plant and neighbouring buildings — we model the snow and the structure.

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