Typed into the wind-pressure formula as if it were a gust, a 10-minute mean wind gives less than half the peak pressure the Eurocode's recommended rule works out for it. The formula is ½ρV², or 0.613·V² pascals with V in metres per second. Singapore's Land Transport Authority (LTA) sets 22 m/s (79 km/h, our conversion) as the 10-minute mean wind for its road elements, and raw that gives 297 Pa. The Eurocode's recommended rule for open terrain at 10 m makes the same mean a 712 Pa peak, by our calculation, so the raw figure is 42% of it, though Singapore's National Annex says the Eurocode's terrain categories do not apply there and 712 Pa is not LTA's design pressure.
A pascal is a newton per square metre, and 297 Pa is roughly 30 kg resting on each, on our arithmetic. The formula gives a pressure and stops there. The load a sign or wall is designed for comes from the wind code for its place, with height, terrain, shape and safety factors that ½ρV² does not contain.
Codes in Hong Kong and Europe state air densities a few per cent apart
In its simplest form, the force on a flat surface is the dynamic pressure times a shape coefficient times the area facing the wind. The 0.613 constant assumes air of 1.226 kg/m³. Hong Kong's Code of Practice on Wind Effects 2019 takes 1.2 kg/m³. EN 1991-1-4, the European standard for wind actions, recommends 1.25 kg/m³ and lets a National Annex, the national supplement to the standard, set its own (§4.5(1)).
The two code values sit about 4% apart, and air at 30 °C and sea-level pressure is lighter than either, about 1.164 kg/m³ by our ideal-gas calculation. Density moves the answer by a few per cent; speed moves it by multiples.
Europe's recommended gust rule describes a peak roughly twice the mean pressure
A 10-minute mean is the average speed over ten minutes, and a 3-second gust is a short burst within it. Because pressure follows the square of speed, a gust 1.5 times the mean carries 2.25 times the pressure. EN 1991-1-4 writes the peak as (1 + 7·Iv) times ½ρ times the mean speed squared, where Iv is the turbulence intensity (§4.5). With the recommended defaults for open terrain at 10 m, the bracket comes to 2.32, by our calculation. Singapore's National Annex is among those permitted to replace that rule.
Hong Kong's Code uses a similar bracket, (1 + 3.7·Iv) squared, to take an hourly-mean matching speed up to its target peak gust pressure (Eq 6-2). With the Code's turbulence profile at 10 m it gives 2.24, though that substitution is our step (Eq 6-2 means tunnel turbulence), and the Code likens its profile to an open-sea one.
A draft World Meteorological Organization project table for tropical-cyclone conditions (Harper, Kepert and Ginger, 2008) puts a 3-second gust at 1.66 times its 10-minute mean over open land and 1.23 times at sea. Squared, by us, those become 2.76 and 1.51 times the pressure. The authors warn that "mean wind speeds per se cannot be converted": the ratio gives the likely peak gust within a period and does not turn a design mean into a design gust. Across the Eurocode, Hong Kong and open-land figures, a raw mean gives 36% to 45% of the peak, on our arithmetic.
Each code publishes its design wind in a different form
EN 1991-1-4 defines its basic wind as "the characteristic 10 minutes mean wind velocity" at 10 m in open terrain (§4.2), with an annual probability of exceedance of 0.02 (§3.4): that is what "50-year" means, a 2% chance in any given year. Singapore's National Annex sets its basic wind in a clause we could not open. LTA's Revision I, in force since 1 June 2026, derives its wind actions from the standard and the annex, and Revision J, due on 1 March 2027, keeps the 22 m/s note unchanged.
BCA's Approved Document of September 2019 listed 33 m/s (119 km/h) as a "3 second gust speed" for the British CP 3 route and the same 22 m/s as an "hourly mean speed" for BS 6399. For plans first submitted from 1 September 2025, BCA's circular APPBCA-2025-03 removed those standards, and the document now requires Eurocode design. Typed raw into ½ρV², the old pair gives 668 Pa and 297 Pa, 2.25 times apart, but each route applied its own factors, so their design pressures were never that far apart.
Hong Kong publishes no speed to type. Its Code tabulates reference pressures for open exposure, 1.98 kPa at 10 m, which through 0.613·V² takes a gust-level 56.8 m/s (205 km/h), on our arithmetic. For Malaysia's MS 1553:2002, Nizamani and colleagues (2018) report a 3-second gust at 10 m, 50-year: 33.5 m/s inland in Peninsular Malaysia and 32.5 m/s on its onshore perimeter.
Hong Kong tabulates pressures that more than double with height
Hong Kong's Table 3-1 runs from 1.59 kPa at or below 2.5 m to 3.70 kPa at 500 m, a factor of 2.33. In EN 1991-1-4, height enters through an exposure factor that, under the recommended open-terrain defaults, grows 1.46 times from 5 m to 20 m and 1.80 times from 5 m to 50 m, by our calculation. That factor already contains the gust bracket, which is one reason the averaging, height and shape figures here never chain into one multiplier.
The Eurocode specifies 1.80 for a raised signboard
A force coefficient accounts for the structure's shape. EN 1991-1-4 gives cf = 1.80 for a signboard raised above the ground by more than a quarter of its own height (§7.4.3(1)), a clause Singapore's National Annex does not list for national choice.
Until 12 October 2026 our wind load calculator defaulted to an unsourced 1.3 for a flat sign or wall, which, everything else equal, gives 72% of the force the Eurocode's 1.80 gives. Its page also described code design speeds as gusts, and it accepted any speed: 1,000 mph on 50 ft² returned 739.77 kN. The revised calculator defaults to 1.8, citing §7.4.3, labels its other shapes indicative and refuses speeds above 120 m/s. It tells readers to use the design wind their code defines and offers no gust conversion.
Both Singapore and Hong Kong list minimum loads and discounts outside the formula
Singapore's National Annex sets a floor that no wind speed produces. Every building "should be capable of resisting, as a minimum" a design ultimate horizontal load equal to 1.5% of its characteristic dead weight.
Hong Kong's Code goes the other way for short-lived structures. Temporary buildings not used for residence and in place for no more than a year may be designed for a minimum of 70% of the loads for permanent buildings (§2.5). For site hoardings and covered walkways, contractors' and bamboo sheds, tents and marquees, the Code takes the pressure as 37% of its reference value, "and no other adjustment factor should be applied".
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