Pergolas are generally constructed with an open-roof design that allows for adequate air circulation and sunlight. the standard pergola height is 8 to 12 feet. But that doesn't always have to be the case. a pavilion is a freestanding pergola with a fixed roof that generally completely covers the pergola. They can also be referred to as gazebos, though that distinction is usually left to smaller and more decorative structures that are found in gardens. pergola beam, 2″×12″ size timber you can span it up-to 20 feet, 2×10 can span up-to 16 feet, 2×8 can span up-to 12 feet, 2×6 can span up-to 10 feet and 2×4 can span up-to 6 feet including Open-Top Pergolas ,Vinyl Pergolas ,Steel Pergolas , Gable Pergolas, Sail Pergolas. for more details of modern pergola designs styles download this file.