I usually build a stair on top of the wall at the wall's highest point where I want it to be roofed over. I have my dwarves go up, build all of the floor, then build all of the surrounding walls to give it support, and then deconstruct the down and up stairs and replace them with the final wall segment.
If I understand you correctly, that's exactly what I tried to do. But the dwarf stood on the roof when he went to deconstruct the down stairs, so he wouldn't have been able to get off the roof again afterwards.
Generally whenever I'm roofing over constructions, I build "scaffolding" staircases up the outside of the building. That way the dwarves can just deconstruct the outside scaffolding once the entire roof is complete
This would work the same way, though, wouldn't it? Don't your dwarves stand on the roof to deconstruct the top portion of that? For me, they don't seem to like working from below.
You didn't happen to issue the deconstruction job while a dwarf was already on the roof, did you?
No, I didn't. There wasn't anyone on the roof when I gave the order, and there weren't any other jobs to be done up there. The dwarf deliberately climbed up onto the roof in order to deconstruct his only way down again - twice!
I put a ramp in place of one of the walls, then deconstruct it and replace it with a wall when the roof is finished. With ramps, there aren't any down stairs to worry about removing.
The ramp is a great idea, when I only need to go up one level. And maybe I could use that as a work-around at other times, too - getting most of the way with a stairs, then building a floor and ramp for the last bit. Thanks!
I appreciate all of the suggestions here, people. Thank-you. I think the ramp idea will work the best for me, though. I'll give that a try.