I keep on getting "Can't keep wall and floor joined" error

[ke.fan.bei]

Hi, when I'm trying to attach my walls to the floor above, I keep on getting the error "Can't keep wall and floor joined". I double checked the walls and it seems to be cutting through the floor and yet I still get this error. How do you fix this? Thank you very much. 

[ennujozlagam]

hello, have you try to click unjoined elements and see what happen or post here some part files your floor and walls only so we can check. thanks

[shellyk]

It's not clear what are you doing when you get this message? 

Could you be changing the wall hight so it's not touching the floor?- this could cause them to unjoin.