Pergola Wind and Snow Load Ratings: What to Look For in Storm-Prone Regions
Two numbers decide whether an aluminium pergola survives its first winter: the wind rating and the snow load rating. Both are quoted constantly in catalogues. Both are easy to quote and harder to back up.
This page explains what the two figures actually mean, why the frame’s wall thickness decides them, and the questions that separate a real engineering declaration from a catalogue number.
What the two ratings actually mean
| Rating | Unit usually quoted | What it describes | What it does not describe |
|---|---|---|---|
| Wind resistance | km/h or m/s | The wind speed the structure is declared to withstand in the specified configuration | Ground-level wind speed at your site, which is affected by terrain, exposure and building height |
| Snow load | kg/m² or kN/m² | The snow mass per square metre the roof is declared to carry | Snow drifting against walls, or ice loading |
| Design wind pressure | kN/m² | Wind pressure used in structural calculation | The same thing as a wind speed rating |
The key trap: a wind rating is quoted as a speed, but the load that actually stresses the frame depends on pressure — which rises with the square of the speed, and varies with height and terrain. Two sites with the same quoted wind speed can put very different loads on the same pergola.
Why wall thickness — not the photo — decides the answer
Load capacity in an aluminium louvered pergola comes almost entirely from the section geometry and the wall thickness of the beam and column. Two pergolas that look identical in a product photograph can differ by a large margin in material — and therefore in what they survive.
| Component | What to ask for | Why it matters |
|---|---|---|
| Beam / track | Section dimensions plus wall thickness in mm | Carries the roof span; the first thing to bend under load |
| Column | Section dimensions plus wall thickness in mm | Carries the whole roof; governs overturning |
| Louver blade | Blade depth and pitch | Affects both deflection and drainage |
| Fixing / base | Anchor specification for your substrate | The strongest frame fails if the base does not |
A supplier who cannot give you wall thickness in millimetres has not given you a comparable specification — whatever the catalogue says about wind.
What our aluminium pergola is declared to carry
| Declaration | Value |
|---|---|
| Wind resistance | Up to 180 km/h (≈ 50 m/s) |
| Snow load | 120–180 kg/m² (≈ 1.2–1.8 kN/m²) |
| Frame alloy | 6063-T5/T6 aluminium |
| Beam | 221 × 55 mm, 2.0 mm wall |
| Column | 122.5 × 58.5 mm, 2.0 mm wall |
| Louver blade | 210 × 122.5 mm |
| Maximum size | Made to order, up to 6 m × 6 m |
| Structural attestation | EN 1090-1 / EN 1090-3, certificate no. TD21162400, models 173 / 180 / 220 / 221 |
Read this as a declaration for the specified configuration — not as an unconditional guarantee for your site. Local requirements differ by region, and the number that matters is the one that applies where you are installing. Ask us for the configuration drawings before you specify.
A note on EN 1090 and load ratings
EN 1090-1 and EN 1090-3 are structural execution standards — they address how load-bearing aluminium components are assessed, fabricated and checked. They do not state a wind speed or a snow load.
That means a pergola can hold a valid EN 1090 attestation and still need a separate, site-specific wind and snow declaration. Treat the two as different questions, because suppliers often blur them.
Declared or tested? Ask which
| What the supplier says | What it usually means | What to ask next |
|---|---|---|
| “Tested to 180 km/h” | Often a calculation or a single test, not a certificate | “Send the test or calculation report, with the configuration it applies to.” |
| “Certified for 120 km/h” | May refer to a component, not the assembled structure | “Which certificate number, which standard, and whose name is on it?” |
| “Meets local codes” | Almost always unsupported | “Which code, which zone, and what is the design pressure you used?” |
| No number at all | Marketing only | Ask for section drawings with wall thickness first |
Unit conversions for international buyers
The same rating is quoted in different units depending on the market:
| Rating | Metric (speed) | Metric (pressure) | Imperial |
|---|---|---|---|
| Wind | 180 km/h ≈ 50 m/s | — | ≈ 112 mph |
| Snow | — | 120 kg/m² ≈ 1.18 kN/m² 180 kg/m² ≈ 1.77 kN/m² | ≈ 24.6 lb/ft² ≈ 36.9 lb/ft² |
Conversions above are arithmetic conversions of our declared values, so you can compare them against a local requirement expressed in different units. Always confirm the requirement itself with your local authority or structural engineer.
What to ask before you buy for a storm-prone site
- Section drawings with wall thickness in millimetres for beam and column.
- The wind rating as a pressure (kN/m²), not only as a speed — pressure is what the frame experiences.
- The snow load rating in kg/m² or kN/m², with the span it applies to.
- Whether the rating is a calculation, a test, or a certificate — and the reference number.
- The maximum span at that rating — a rating at 3 m does not carry over to 6 m.
- The base and anchor specification for your substrate (concrete, paving, deck).
Frequently asked questions
What wind speed should a pergola be rated for in a storm-prone region?
There is no single number — it depends on your location, exposure and the height of the installation. The practical approach is to ask your local authority or structural engineer for the design wind pressure for your site, then ask the supplier for a pergola declared at or above that pressure in the exact configuration you are buying.
Is a 180 km/h wind rating the same as surviving a 180 km/h storm?
No. A wind rating describes the wind speed the structure is declared to withstand in a specified configuration. Real storm exposure depends on terrain, gusts, height and how the pergola is anchored. Treat the rating as one input, not a guarantee.
Do EN 1090 certificates cover wind and snow loads?
No. EN 1090-1 and EN 1090-3 cover the execution of load-bearing aluminium and steel structures — assessment, fabrication and workmanship. Wind and snow performance are declared separately, so ask for both.
Why does wall thickness matter more than the headline rating?
Load capacity comes mainly from the section geometry and wall thickness of the beam and column. Two pergolas can look the same in a photograph and differ significantly in material, which is why a rating without a section drawing is not verifiable.
Can I install a pergola on paving or a deck instead of concrete?
The frame’s rating assumes the base can take the load. Anchoring into paving or a timber deck may require a different base detail, and in some cases additional ballast or a concrete pad. Confirm the base specification before ordering.
Does the maximum size affect the rating?
Yes. A rating is declared for a configuration — a given span and size. A structure at its maximum span does not necessarily carry the same wind and snow rating as a smaller unit, which is why you should always ask for the maximum span at the rating you need.
What documents should I request for a storm-prone installation?
Ask for the section drawings with wall thickness, the wind and snow declaration with the span it applies to, the structural attestation with its certificate number and scope, and the base and anchor specification. Together these let your engineer check the structure against local requirements.
Specifying for a high-wind or heavy-snow region?
Send us your site’s design wind pressure and snow load, plus your intended size and installation surface. We will confirm the configuration and the drawings that back the declaration.
Contact: browncardon.global@gmail.com · Chongqing, China