This is the most misunderstood specification in the category, and the one most likely to be quoted misleadingly. A number on a product page that reads “wind resistant up to 130 mph” is doing a lot of unexamined work, and it is worth knowing exactly what it does and does not tell you.
What Wind Rating Does Your Lot Need?
Rating Check
What Wind Rating Does Your Lot Actually Need?
Minimum rating to shop for
90–110 mph
A standard 6063-T5 frame is genuinely enough here. Spend the difference on span or a longer motor warranty instead of chasing a rating you will never load.
How to Read a Published Wind Rating
The loaded condition is the whole question
With louvers rotated open, a pergola roof is a series of thin vertical blades and wind passes between them. Load is modest. With louvers closed, that same roof is a solid horizontal plane, and wind flowing over it generates uplift — the same force that lifts an aircraft wing, applied to a structure held down by four footings.
Those two conditions are not close to each other. A manufacturer quoting an open-louver figure without saying so is quoting the easy number. Ask which condition the rating describes; if the answer is vague, treat the rating as unverified.
Design wind speed is not the gust you will experience
Structural wind ratings reference a design wind speed defined in the building code — a statistical figure tied to a return period, measured at a standard height in open terrain. It is not the peak gust your weather app displays. This is why a 110 mph rating is genuinely adequate across most of the inland United States even though local gusts exceed that number occasionally.
Ratings assume correct installation
Every published figure assumes the structure is anchored as specified: correct footing depth, correct anchor type, correct torque. A 160 mph frame bolted to a two-inch decorative slab is not a 160 mph structure. The rating describes the assembly, not the extrusion.
What Actually Determines the Rating
| Factor | Why it matters | What to look for |
|---|---|---|
| Alloy and wall thickness | Governs how much the header beam deflects under load | 6063-T6 heavy-wall on spans over 14 ft |
| Post-to-base connection | Where uplift is actually resisted | Through-bolted bases, not surface plates with short screws |
| Footing size and depth | The mass holding the structure down | Manufacturer-specified footing drawing, below frost line |
| Louver retention | Individual slats are what leave first in extreme wind | Positively retained pivots, not friction-fit end caps |
| Span | Longer beams deflect more at the same load | Intermediate support or heavier extrusion over 16 ft |
Snow Load Is a Different Number Entirely
Wind rating tells you nothing about snow. Snow load is a downward, sustained, static load, expressed in pounds per square foot, and it stresses the structure in a completely different direction.
The counterintuitive part: on most louvered systems the correct storm position for snow is open, not closed. Open louvers let accumulation fall through rather than building a load on a flat slat roof. This is the opposite of the correct position for wind and rain, and it is exactly the kind of thing that should be confirmed with your manufacturer in writing rather than assumed.
| Region | Typical ground snow load | Practical implication |
|---|---|---|
| Southern US | 0–10 psf | Not a design driver |
| Mid-Atlantic | 15–30 psf | Confirm the figure; most units clear it |
| Great Lakes / New England | 40–70 psf | Requires a published snow figure, not just wind |
| Mountain West | 70–150+ psf | Specify explicitly; many residential units are not rated for this |
Ground snow loads are code-published and vary sharply by elevation within a single county. Your building department has the governing number.
Questions to Send the Seller
Copy these into an email before you order. The answers — and how quickly they arrive — tell you as much about the company as the specifications do.
- What is the published wind rating, and does it apply with louvers open or closed?
- What is the published snow load in pounds per square foot?
- Do you supply a stamped engineering letter, and for which jurisdictions?
- What footing detail does the rating assume?
- What is the recommended louver position during high wind, and during snow accumulation?
- Are louvers positively retained at the pivot, or friction-fit?
Insurance and Liability
A permanent structure that fails in a storm and damages a neighbour’s property is a liability question, and the two things that decide how that conversation goes are whether it was permitted and whether it was installed to the manufacturer’s specification. Both are documentation you should have and keep. An unpermitted structure is not just a code problem; it is a claim problem.