Patio Arbor beam size

Robert L

I am building an arbor the width of my house. I have four 6x6 post 12.5 feet apart center to center. I was planning to put two 2x10 one on each side of the post bolted with 1/2 inch carriage bolts to each post. Will this be a large enough beam to support the 12.5 span? the 2x6's from the house to the beams will be spaced 2' apart with 2"x2" running opposite spaced 4" apart.

Daniel Holzman

Presumably you are building off of plans, they should size the structural elements for you. If you get a building permit, the building official should be able to help you with sizing the elements. Sizing elements is typically a job for a structural engineer, however you probably don't want to pay for one, so my suggestion is to find some plans in a book, get a permit based on the plans if it is necessary, then follow the plans. Getting structural elements sized by an internet committee is trouble, are you really going to trust the opinion of someone who you never met, has not seen your location, is probably not familiar with your codes, and has no personal stake in the outcome?

Wildie

I take it that your house is about 37.5 feet long! (3X12.5)

Will you be using a ledger board on the house and using joist hangers to support the 2X6 (rafters ?)
I just finished building a porch roof and the beam required 3-2X10's laminated together on a 13 foot span to support the weight of the rafters, the roof sheeting and roofing material. The snow load here is 40 psf.
An open arbor will have little problem with snow load, so its likely that 2-2X10's will be more than adequate!
Rather than use lag screws, I would use 2 threaded bolts, long enough to run through the 2X10's and the post!