I can help
Can I get back with you a bit later this afternoon?
I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.
For your center 17' span beam, if you wanted to use conventional lumber, you would need a quadruple 2x14 Douglas-Fir (#2 grade) beam
For your two exterior 17' span beams, if you wanted to use conventional lumber, you would need a triple 2x12 Douglas-Fir or SPF (#2 grade) beams
I can give you a couple engineered wood options for your 17’ span beams:
Center Beam 5-1/8” x 9-1/2” Boise Glulam 24F-V4/DF
Outside Beams 3-1/8” x 9-1/4” Boise Glulam 24F-V4/DF
These are Boise Cascade products and you can go to the following link to find distributors in your area.
You will need to have a local engineer detail your connections, determine foundation requirements, and check your structure’s lateral stability.
You will need to make sure your Glulam Beams are treated for exposure to weather
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Let me know if you have any more questions