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Class 1 & 2 (Agricultural buildings)

posted 18 Mar 2013, 05:36 by David Mair   [ updated 13 Apr 2013, 15:33 ]
The difference between BS 5502 class 1 & 2 (Agricultural buildings)

The higher the class number the greater the risk that the building will collapse under wind or snow loads.

Therefore class 1 is designed for a 50 year design life and a stronger building than class 2 which is only design for a 20 year design life.

Most farm buildings are designed to class 2, with only buildings with a high human occupancy designed to class 1 (like farm shops). 

After quite a lot of buildings collapsing in the last few winters farmers are asking about different bay sizes 15 ft and 20 ft, thinking that narrower bays will help with snow loading. This in some cases may be the case but the steel and purlin size tends to be reduced to the minimum requirement to only pass as class 2. So a 15ft bay designed to class 2 and a 20ft bay designed to class 2 should both carry the same snow load before collapse. 

If you are worried about snow buildup on a new building you should ask for it to be designed to class 1. A class 1 structure will take about a third more weight than class 2. Also remember that the area of country you are in and how high above sea level all have an impact on the structural design. Some shed builder supply a standard kit buildings but it may not be suitable for your site if you are in an exposed site or high above sea level. Contact us for further information or help in making these important decisions.

Agri Design
David Mair,
18 Mar 2013, 05:36