Most ceiling joists are not strong enough to support a swing, but there are some that are. To determine if your ceiling joist can hold a swing, you will need to know the dimensions of the joist (width, depth, and length), as well as the type of wood it is made from. The most important factor in deciding if a ceiling joist can hold a swing is its width; the wider the joist, the stronger it will be. If you're unsure about whether or not your ceiling joist can hold a swing, it's best to consult with a structural engineer or contractor who can assess the situation and give you a definitive answer.