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Why a 20degree pitch roof is more wind-resistant
Nearly all large commercial marquees use a 20degree angle for their pitched roofs, this means a 1m rise on 6m wide structures (2m leg = 3m apex height, 2.3m leg = 3.3m apex height) and a 1.5m rise on 9m wide (2.3m leg = 3.8m apex height).
Even though a 20degree angled roof costs a little more to manufacture than a 30degree roof say, it is used because it is more wind-resistant.
As the roof angle increases the ridge of the marquee gets higher, the surface area of the roof increases and the forces that roof has to withstand go up exponentially. If the roof doubles in height the force it has to withstand is actually quadrupled.
The lower the apex height, the more wind resistant a structure will be.
Clearly (especially in Britain) a marquee has to be able to deal with a lot of rain. Through many years of experience the industry has found a 20degree roof the most durable at dealing with the wind and rain common in the UK.
Note: Smaller structures (3m or 4m wide) can cope better with 30degree roofs, especially when additional roof braces are used to strengthen the framework.
We are always happy to offer more customised advice for your event, please contact us giving a few details of the event you are planning (type of event, space available, number of guests and diagrams/photographs of the site if possible) and we will be more than happy to advise on your options.
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