Hi,
I am currently creating a building and have an issue with aligning of two faces i.e. explaining from the beginning, I made up some separate models, then aligned them in some order. Then i mirrored them and added an array modifier by x and z axis to make the walls of the building. 
The building have also got a concave corner. Now I need to align each wall to the corner first, copy that, rotate by 90 degrees and align by faces once again and repeat these steps.
I have got “align by faces” addon but it doesn’t seem to work and I have also got “Precise alignment” tool which I know how to use. I don’t know if I haven’t messed up things by setting apply button to both mirror and array modifiers.
Cheers,
Emedee.