How do I delete, dismantle constructions

[Muttley]

I accidentally built a floor over a staircase and now I can't open it back up. I would also like to open a wall in one of my buildings but I don't know how. Yet it says you can?

[Deviant]

The mining option (m) then click the red circle over the stairs (x)

That's the deconstruct tool.

[TimeVampire]

In the mining options, one of the options is to deconstruct constructions. Highlight the area to be removed, and a dwarf will come and tear up the floor/remove the wall. They have to be able to reach an adjacent tile in the case of a floor, since dwarves will not remove a floor they are standing on (for obvious/selfish reasons).

[Muttley]

Originally posted by Deviant:

The mining option (m) then click the red circle over the stairs (x)

That's the deconstruct tool.

Originally posted by TimeVampire:

In the mining options, one of the options is to deconstruct constructions. Highlight the area to be removed, and a dwarf will come and tear up the floor/remove the wall. They have to be able to reach an adjacent tile in the case of a floor, since dwarves will not remove a floor they are standing on (for obvious/selfish reasons).

Of all the places for it to be, mining was the last thing I would've expected.

[AlP]

Originally posted by Muttley:

Of all the places for it to be, mining was the last thing I would've expected.

It also requires a mining pick now.