Floating stair landing

[RollingStone]

I've add two stair landings to exits from the house.  However, each one is too high by about 4-6" so instead of being below the respective door they are above the door.  When I select the object, I can move it in the x-y plane but can't seem to move it down - it's locked at the wrong height.  Is there some settings I need to modify to get the stair landings lower?

 

Thanks

 

[solver]

Open the landing and