You mentioned steeples first. That may have been a mistake, but I will answer anyway. You climb a steeple from the inside and exit from a door at the base of, or on, the spire. From there we would typically build a platform on which to erect our ladder to go as far up the spire as needed.

All the stacks I worked on, save one I can remember, had beacon lights that needed regular maintenance and all had ladders built in. The ladders did not go all the way to the ground/roof level. That was to keep unauthorized folks from climbing it.

I remember two stacks had permanent catwalks around the top. One of them was quite corroded and not a comfortable place to walk. Like a sibling comment mentioned, that difficulty in maintaining them is a reason why many stacks don't have ladders. Some stacks that don't have them once did, but they were removed due to corrosion.

As far as access, all of the stacks I worked on had only one ladder. If the job was small and there was work that needed to be completed on the other side we had two options.

1. If the repair was low enough we could attach the ropes from which we hung our bosun's chair at the top and swing around to the other side.

2. If the repair was too high to do that or too involved we would build a scaffold all the way around the stack.