In the original design they called for a woven wood pergola but ran into a couple of issues. The biggest issue was the wood would have made great tinder and had it caught fire the entire thing would have been ablaze pretty quick. The building department would have required a costly fire sprinkler system above the pergola that would have also taken away from the aesthetics. The solution was to build it out of metal instead using a stamped aluminum round bar in three different diameters and powder coating in a few different colors to get a similar look without the fire hazard. The end result was a beautiful pergola that will last decades with very little maintenance other then the occasional washing which can be done with a pressure washer.