I am in the design phase for a Pergola I am going to construct and want to know if my unsupported length is too long. I am currently planning on a freestanding structure 14'4" x 5'10" with 6"X6" posts at the corners. The girders and rafters will be 2"X6" layed in a grid pattern, evenly spaced. All construction is with Cedar. Is the 14'4" too long of an unsupported length for the dead weight of the pergola? Should I plan on putting another 6"X6" post in the middle. I am not planning on this bearing any load besides the weight of the structure itself.
For 14+ feet a 2x8 would be too small. Double 2x10's, one on either side of the 6x6 along the 14 feet. I would also put spacers every 3 feet or so to unitize the 2x10's. The 2x6's on top spanning the 5'10".