support
I have a 12' x 12' deck with posts set at 6' on the sides & 4' on the front. There are 2 x 6 along the outside at the top of the posts. I would like to add pergola beams across the top,side to side to cut the sun a bit. Will the 2 x 6's hold those beams or should I add another 2 x 6 to the inside for more support?
Thank you.
Blue Dashed Line: Your 3-2x12 Beam
RED X: 6x6 Posts
**post edited to match additional info from comments.*
it this case, it is not a home improvement project. Since it is a commercial building, you really need to have an engineer design a fix. the liability is to great in rental or commercial property not to have it endorsed. Don't take a cheap fix, it will bite you. The safety of a lot of people depend on how you fix the problem.
Best Answer
A 2x6 weighs about 2 lbs. per foot, so each 2x6 will weigh about 2 lbs. x 12’ span = 24 lbs.
Half the weight will be carried by one end, so the weight on each end will be about 12 - 16 lbs. per foot (if the 2x6’s are 12” o.c.) and there are miscellaneous 2x2 wood strips on top too.
A 2x6 roof joist support can carry about 150 lbs. per foot, depending on the species and grade.
So, structurally you do not need to add another 2x6 to support your pergola Beams (2x6’s), but you may want to for appearance.
See these designs
Remember, the best wood for exterior use and natural finish will be cedar or redwood...but you can always paint pressure treated wood.