pergola beam size

Hi . A little off the gardening section but pertaining to plant stucture support . I have been trying to find information on building a pergola carport . The area is 20'x 30' . The 30 ' is the entrance to the carpot . What I want to do is put a cedar beam across the opening without a center support . Is this possible ?
If possible , what sizes . Eg 2x6 ', 2x8'or larger and what length ? The carport is by the garden and I hope to incorporate some climbing somethings .
If any gardeners have had experience with this type of project I would appreciate advice or possible source of info .
On the deck 12 x 18 , I would like to put hanging baskets .
I live on Saltspring Island and haven't found the right knowledgeable person yet .
Regards .
Roger

 

2x8 should do it, I built a pergola last spring.

4 6x6 posts in the ground and 2x8s running across

 

Bullseye . I am trying to getting a cutting list together . The two mini mills I contacted won't answer any questions on the phone . They keep saying - give me a cutting list .
The determing factor on building will be the cost of 2x8x30 foot beams .
Thanks for the info .
Roger

 

I would refer you to a structural engineer if I knew one.
I had problems with 2 x 8 beams at 22 feet least year and ended up having to take them down and replace them with 3 2 x 12"'s

I got a 5" sag in the center.
p.s. My lumber yard spec'd the 2 x 8's - go figure?

They were not cedar but engineered beams so I can't tell what the situation would be with cedar at 30 feet.
Never hurts to call in a pro for a few bucks.

Regards

Bob

 

Thanks Bob . I am considering an engineer . I was cautioned re sag . The front porch has two 4"x10" x15' for a span of 30' which are supported at each end . I was also cosidering the side which will be 22' . Nice to know a 2x8 didn't do the job. My concern with a center support is someone hitting it with a car . May be the only way to go .
Roger

 

I hate being the bearer of bad news Roger but best to know now .
You could span it with a steel beam and skin it in with cedar but that could get pricey.
I'd be interested to see what an engineer thinks.

This calculator will give you some numbers to start playing with:
http://www.awc.org/calculators/span...d=10&submit=Calculate+Maximum+Horizontal+Span
Good luck
Bob