Frequently I get plans for a steel canopy to cover a small to medium area. The plans usually call for wide flange steel beams, purlins and steel roof decking. When I see these plans I wonder if the architect or engineer was aware of the benefits of aluminum.
Aluminum roof decking can span up to 18′ without purlins. Post spacing is 18′ – 20′. The footings are also much smaller. This, of course, means the canopy can be built at a much lower cost. This type of canopy is ideal for loading dock covers, lunch shelters, smoking shelters, material and equipment covers, etc.
If you need to cover a very large area and keep it clear of columns or posts than steel may be better. Steel wide flange beams come is much larger sizes and can be engineered to span large areas without posts or columns.