Structural Pergolas are larger commercial style pergola structures with long spans between posts. All beams are A Beam filled. With our Steel Insert System (US Patent #8061106) a four post pergola can be as much as 16' x 16'. There are other options available to save money as well as keep the open area under the pergola (see Reinforced Pergolas). For additional information on stuctural pergolas please see our Steel Insert System page. For information regarding the differences between reinforced and structural pergolas, click here.