hi,
 
i suppose this is a really basic question.. how do i, after creating a new face, add it to already existing object.
so i dont have a new object for every wall, but an object that consists of more faces.  
now, i create a new face but it automatically creates new mesh. i want to add the new face to already existing mesh.
thaks for answers
 
tika

Ensure the first face is selected, then add additional faces to it.