Free Tool · EN 1991-1-4:2005

Wind Load Calculator

Derive EN 1991-1-4 wind actions for rectangular buildings. Computes basic wind velocity vb, mean wind vm(z), turbulence intensity Iv(z), peak velocity pressure qp(z), external pressure coefficients cpe,10 for walls (zones A–E) and roofs (flat/mono/duopitch), internal pressure cpi, and net pressures wnet per zone in kN/m².

v_b
27
m/s basic wind
q_p(z)
1.007
kN/m² peak pressure
Base shear
1.1
kN/m — windward
Roof uplift
2
kN/m — γ_Q=1.5
Step-by-step derivation
1. Basic wind velocity v_b (§4.2)
v_b,0 = 27 m/s × c_dir·c_season = 1.0 v_b = 27 m/s
2. Roughness c_r(z) + mean wind v_m(z) (§4.3–4.4)
Terrain II — Open country with low vegetation z_0 = 0.05 m z_min = 2 m k_r = 0.19 c_r(8m) = 0.964 v_m(z) = 26.03 m/s
3. Turbulence I_v(z) + peak pressure q_p(z) (§4.4–4.5)
I_v(z) = 0.197 q_p(z) = [1 + 7·0.197] × ½ × 1.25 × 26.03² = 1.007 kN/m²
4. External pressure coefficients c_pe,10 (§7.2)
h/d = 0.667 → zones A–E interpolated from Table 7.1 A: -1.2 B: -0.8 C: -0.5 D: 0.756 E: -0.411
5. Internal pressure c_pi + net pressures w_net (§7.2.9)
c_pi = +0.2 (positive) / -0.3 (negative) — governing per zone w_net(D) = 1.063 kN/m² w_net(E) = -0.615 kN/m²
Pressure zone diagram
WIND D A B C E F G H I (±) ← d → EN 1991-1-4 Fig 7.5 / §7.2.3 h + -
Elevation + plan view — wall zones A–E, roof zones F–I (flat roof shown). Green = positive pressure. Red/amber = suction.
Wall pressure coefficients c_pe,10 + Roof pressure coefficients c_pe,10
Zonec_pe,10w_e (kN/m²)w_i (kN/m²)w_net (kN/m²)
Wall A -1.2 -1.208 0.201 -1.409
Wall B -0.8 -0.806 0.201 -1.007
Wall C -0.5 -0.503 0.201 -0.704
Wall D 0.756 0.761 -0.302 1.063
Wall E -0.411 -0.414 0.201 -0.615
Roof F -1.8 -1.813 0.201 -2.014
Roof G -1.2 -1.208 0.201 -1.409
Roof H -0.7 -0.705 0.201 -0.906
Roof I_pos 0.2 0.201 -0.302 0.503
Roof I_neg -0.2 -0.201 0.201 -0.402
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Full wind profile for multi-storey buildings
Pro unlocks multi-storey wind profile (z-dependent q_p), iterative gust factor c_sc_d per Annex D, and dynamic response spectra — automatically applied to every beam in your drawing set.
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Frequently asked questions

What is q_p(z) in EN 1991-1-4? +
q_p(z) is the peak velocity pressure at height z, combining mean wind pressure and turbulence: q_p = (1 + 7·I_v(z)) · ½·ρ·v_m²(z). For terrain category II and h = 8m with v_b = 27 m/s, q_p ≈ 0.85 kN/m².
What do wall zones A, B, C, D, E mean? +
Zones A, B, C are side-wall (suction) zones with c_pe ≈ −1.2 / −0.8 / −0.5. Zone D is the windward face (positive pressure, c_pe up to +1.0 for h/d ≥ 5). Zone E is the leeward face (suction, c_pe ≈ −0.3 to −0.7).
How do NL and DE national annexes differ? +
NL uses two zones: I (inland, 22.5 m/s) and II (coastal, 27 m/s). DE uses four Windzonen: 1 (22.5) to 4 (30 m/s), with a mixed roughness profile for inland sites. BE uses a single zone at 26 m/s.
When is c_s·c_d ≠ 1.0? +
For buildings < 15m the structural factor is 1.0. For taller buildings, Annex D provides an iterative procedure accounting for resonance and background response. FrameAI Pro runs the full Annex D calculation.