Building a covered porch onto the front of my home, 6′ deep by 16′ wide with a gabled roof. Keeping the thing open and airy – no siding on the gable end, no blocking between rafters, no ceiling. I’m planning on 6×6 for the corner posts, and am wondering what size beam I’d need across the front of the porch to support the gable roof without a center post. I’d like to avoid the center post if possible. Thanks.
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What is your design load for the roof? (wind uplift and/or snow download?)
I'm trying to picture this. Are you running a 16' beam from post to post with a post in the center of this beam to support a ridge board?
Exactly. No snow load, not sure how to judge wind uplift. Picture this porch http://www.rosschapin.com/Plans/Cottage/Erin%20Cottage/Erin.html but 16' between posts. I'm afraid I'll need a beam so large as to look out of place and I may be better off with a center post as well.
In this case I might check with an architect. Or another posibility, use a wide flange steel I beam and wrap it with wood and forget the architect.
I'm like Mike - if the joints are fastened right, this does not need a beam, it is a tie.
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I agree, with two ties you are safe. We're only talking about six feet so the roof sheathing is going to go from the end of the gable all the way to the existing roof. I don't see how the it could spread even without the second tie.
Prescriptive code says you need ties spaced no more than 48", thus the need for the second. It probably wouldn't go anywhere with just one though.
I would be inclined to double the ties up for looks. A single 2x spanning 16' is going to look pretty lonely.
or make it something decorative.
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forgot
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Without a center post, all the beam is doing is preventing the rafters from spreading so it can be fairly small--it's acting as a rafter tie, not a beam. You would need another rafter tie between that one and the house to meet code. Single 2x6's would probably be big enough, but a 2x8 would look better.
Run it by your building inspector first though.