I am building a foot bridge over a creek. I don't want to try and sink footers/posts in the creek itself, I am wondering how long a 2x12 can span. I am able to find 26 foot treated 2x12's locally. If I sandwiched two of them together on each side of a say a 3 foot wide foot bridge would that work? The ends of the bridge will be treated 6x6 posts (so 4 total). The span between posts will almost be the full 26 feet. My question is:
Thanks David
Would a flat truss be a practical alternative?
I don't know for sure, but you can play with some numbers here and get a rough idea
According to this, you need some support, but this may be to drive across.
If you are thinking of building any bridge with a span greater than 20 feet, you better get a structural engineer involved, plain and simple.
The easy answer is engineered trusses. You can do that with 2x4s in most cases. The trick is finding someone who can assemble them with stainless truss plates.
Are you the new contractor for the Florida International University pedestrian bridge repair project?
Anyway, maybe try this design:
Using that span calculator if you build it 3 ft wide, use 12" spacing, which would be four 2x12, best wood, accept maximum deflection, minimum loading, it's just barely at the limit at 26 feet. I think others are right here, there are other better solutions, but they are likely going to cost more and be more involved. Another factor to consider is how sound the earth is on either side for the support.
He could always go with a swinging bridge.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required