This approach is even better with deck railings.

In this image, the top elements represent the intersect as well as a slightly smaller negative object. In the center you see all the posts and rails. When you group all these, and change the material, you get the posts and rails seen at bottom.

This technique is extremely versatile. For example, all your rails for a given deck level can be defined by only two objects, no matter how complex the external contours are of the deck.