Building Wall Over Floor Dwarf Fortress

Implied by constructing walls on the z level below.
Building wall over floor dwarf fortress. Bridges can be built b g of metal stone or wood. Just leave a hole where you want to build the walls. A floor is a fixed map tile that creatures can walk upon as opposed to movable features like bridges and hatches a floor can be. Constructed floors can be built over natural artificial.
Note that the different types of floors may be combined. And in other cases my dwarves would climb outside during a siege and promptly get murdered. Sloped roofs can be created by building a row of walls adjacent to the top of a wall a row of ramps can then be built directly on top of the wall giving access to the top of the adjacent wall. Over walls 2 z levels high.
Just build a stair to allow your dwarves to stand on top of the wall from the outside of the building then build the floor. Walls may be built on any square which does not already contain a structure provided your dwarves can reach an adjacent square this includes building a wall over empty air next to a floor allowing for the construction of inverted pyramids. So long as the wall is touching a floor somewhere it wont cave in 45 degree angle is not considered touching. Diagonals cannot be built from nor will they support constructions.
Remember though you can t build walls on top of a floor. They can be used as is and use less materials than a constructed floor of the same size serving the same purpose. Walls may be built on any square which does not already contain a structure provided your dwarves can reach an adjacent square this includes building a wall over empty air next to a floor allowing for the construction of inverted pyramids. Walls shouldn t be climbable they are auto smooth after.
However building a bridge over an existing floor will allow those floor tiles to be deconstructed and the material recovered. Diagonals cannot be built from nor will they support constructions. Artificial as created by mining. Both against invaders and for my dwarves.
If you insist then you can take the floor away after building the wall and then reinstate it one floor up to act as a scaffold for the next layer of wall. I ve had multiple occasions where a goblin siege would simply climb over the walls of my fortress and commence the killing. If you want them to raise or lower they must be linked to a trigger see below.