GardenStructure.com Pergola Design Rules:
- More than 12' spans are expensive, use sparingly.
- Pergolas should have more than 4 posts whenever possible, 4 post pergolas always have that "Amateur Look".
Not only is it a design faux pas, but it is just plain dangerous to run that close to the edge. First strong wind—first sign of rot—first tremor and your dream pergola with only 4 posts is likely to hit the ground. (If not designed properly)
What are they thinking?
A post stuck in the ground will never move?
A post perched upon a sonotube has infinite lateral strength?
Maybe that the footings are the difficult part of the job so they only want to do 4?
Or is it that they wouldn’t want anything to obstruct their wide open view. Why bother building a pergola if you don’t want to look at it. Does a pergola not frame the view?
Then again when you look at the pergolas typically built by deck contractors, with their 4 posts and their 2 stacks of sticks designs, I would prefer not to look at it either.
Go ahead—ask if we can give you plans for a 16 x18 pergola with only 4 support posts and try to cut me off before I explain why that is a really—really bad idea.
We can design a pergola that size with only 4 posts… the posts will be massive (and come at a premium), the footings are likely to be 2-3’ in width, (also at a premium), and the beam is likely to be more than 16” high, (heavy premium-and will obstruct some of your precious view).
If you are willing to shorten up the spans and use 8 or 12 posts rather than 4 it will be about ½ the price—and just my opinion, but I think it will add architectural intrigue to your home and frame the view rather nicely.
Here’s another article about the same subject: large span pergolas