Hanging a Jhula Swing

[Jon Robinson]

I asked this question in another forum but think it is better suited here. I am trying to hand a Jhula swing from a doubled I joist. The joist covers about a 20 foot span and carries the load of a cathedral ceiling end. The joist is properly supported on either end to the ground and I wanted to know if adding a swing which would weigh about 100lbs and with people maybe 3 to 4 hundred more would that joist be able to support that weight. Granted it will not be under that load constantly but I wouldn’t want to stress the beam being as though it is carrying the load of a pretty high roof. Any advice?