Thanks for the input and suggestions. If I want to sandwich the posts between the 2x10s, I will either have to bury less post, lower the "roof", or buy longer posts. Which is the best option? Are 2x10s necessary, or would 2x8s function (and look) well? I would love to put in a detail like oval windows, but to keep costs down, this may be a diy job, and we don't really have the skills to pull it off. I'm the family handyman, so I'll be relying on my husband for help with the heavy lifting and supplying the direction myself. He would rather be playing golf. Once the thing is up, I'll look at making panels of square trellis to insert in the spaces along the back, which faces a street (corner lot). I'm thinking of skipping the readymade lattice and making my own, so I'll have to figure out the details of framing and attaching it to the posts later. Someone on one of the forums posted some photos of a pergola they built attached to their house, using fir, I think. Would it be reasonable to use PT for the posts and fir (or something else) for the rest? I'd love to use cedar, but the cost is more than I care to spend. Here's the site where it will go. The foreground has been ready for it for two years, the plantings near the house are still quite small.

A center post would interfere with the use of the space covered by the pergola and look terrible, in my opinion. What you have will sag a little, but not enough to make it look bad, or justify adding something to it that will detract from the design. It probably won't sag much more that it already has naturally, but, if it bugs you in the future, you could disconnect the knee braces, jack up the center of the spans somewhat higher than you want them to be, and reattach the knee braces to support this higher center position. If you do it right, the center will settle down in about the right place once you remove the jack. My advice is to leave it be for now, and consider planting grape vines on the short sides that will give you shade in the summer, and hide any sagging as the vines climb over the structure. And you'll get fruit!

Lisa, I've got lots and lots of Queens Wreath seeds. I could start them for you, but for postage-sake, it might make more sense to just send them to you in exchange for seeds - maybe some choy sum or four o'clocks? email me at susannahnesmith (at) yahoo.com

I'm sure you know that a pergola typically has beams for the roof which leaves the area below open to rain and snow and there will be less shade on hot days, while the pavilion has a solid roof cover. My choice would be dependent on the climate, whether there are other outdoor covered areas to use during inclement weather, and how it will be furnished (damp cushions are no fun). If you have plenty of other covered areas, sometimes it's nice to have a bit more open sky. Yes, you can float it and use hardscape paths to connect it to the existing hardscape.