Joist hangers and their close brother beam hangers are always responsible for bearing a load. With this in mind, it is very important to use the proper size of nails to keep the structure strong. Often times if a homeowner or even an inexperienced contractor uses the improper nail size it will cause problems with the joist hangers, either providing not enough strength or using too long a nail could damage the existing beam.
It is recommended that you use 3 inch nails with your joist hangers. This will ensure strength in the frame and will not be too long of a nail that it would cause any damage. 1 ½ inch nails are often used but can sometimes be unable to hold lots of weight like in situations where a deck has actually broken away from the joist hangers.
Screws should never be used with joist hangers, as they do not have the proper shear strength. Be sure to use the required joist nails (1 ½ inch with #10 stamped on the head) to face the joist hangers and 3 inch 10D galvanized common nails to double shear and/or toenail through the side slots of the joist hanger.