Expert: Nazim Nice - 5/13/2010

Question
Hello,

I'm sure you must be tired of answering these sort of questions, but I've searched and googled and bribed friends for information, but the answers I'm getting do not solve my puzzle.

So, here goes. I have a brand new house with a big yard. I live in Delaware Ohio where recently we had thunderstorms with wind gusts of upto 50Mph. We get lots of snow and during summers it gets plenty hot.

We've recently completed a 20x15 paver patio, and would very much like to build a pergola over it. Now, if you would imagine that the paver patio is 20 feet long and 15 feet wide, it's perpendicular to our house. I would like to build the pergola parallel to the house, meaning 20 feet wide by 15 feet across. The pergola and the patio would become a plus sign, so to speak.

My questions:

1. Using just 4 6x6 posts, how do I construct this project?
2. Is the standard here of 3 feet deep concrete post hole enough?
3. Would it be safe to build using simpsons tie cbsq (http://www.strongtie.com/products/connectors/cbsq.asp) for the posts?
4. How do I support either 2x10s or 2x12s across the 20 foot span? Metal braces?

I would like this to be an investment for the next 10 years or so. Thank you in advance for you valuable answer.

Answer
Hi Altoo,

Even though this sounds like a simple project, the reality is that you really need the help of a structural engineer to make your structure safe and sound. I can't answer your structural questions, but here are a few design suggestions:

For a structure that is 20x15, 4 posts that are 6x6 may look too spindly to support this structure.  I would consider 6 posts, or beef up the posts, or perhaps do a series of posts in the corner (like 3 in each corner such as this project: http://www.motion-space.com/projects/kent-outdoor-kitchen.html).  

Also, keep in mind that the structure needs to be braced for high winds. In the project link above, we used steel trellises between the posts to help create stiff corners that resist lateral (or sideways) movement.  

Good luck!

Nazim Nice
Principal / Architect
http://www.motion-space.com
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