I’m working on my first big project. I have a 10×16 pergola. The long side includes three 6×6 posts 8 ft away from each other. There is another row of 3 posts 10 ft away perpendicular to those posts. All posts are set below the deck on concrete footers and deck posts. Posts are notched on top to recieve 2×8 beams. Currently have 2×6’s running the 10 ft length underneath the beams to give some stability. My wife was wanting to hang a rather large swinging day bed from the pergola on the side where the grill is next to the fence. I was wondering what size rafters I would need to support that kind of weight if it’s spanning 10 ft. I currently have 2×6’s bought for the rafters but from what I read I will need something bigger. I would prefer to avoid 2×8’s just so the top doesn’t get taller. Would 4×6’s work as rafters? Thanks for the help. Pictures are in the link below.
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https://www.homedepot.com/c/ah/how-to-hang-a-porch-swing/9ba683603be9fa5395fab9011729f559
above might be worth a read.
but it sounds like the day bed might be bigger, and attach at 4 points vs 2.
one thing to consider is spreading the load over several rafters. Blocking between rafters could be used to transfer the load to a pair of rafters, and can even be extended to further transfer load to adjacent rafters.
double 2x6 is stronger than a single 4x6.
if a rafter table shows you could get 30 PSF live load from a ten foot span of 2x6 at 16 inch centers, live loads on a 4 ft section of the 10 ft span would be 30 times 40, or 1200 Pounds. (the forces are different, since span tables assume a floor deck to help spread the loads)
Adding a swinging bed increases the need for braces to keep the columns vertical. This is especially true if there is any way the swinging bed could contact a column directly or indirectly.
This is an informal discussion. If you want a solid answer, might want to contact an architectural engineer. They will get you an answer for the minimum structure for the application.