Is it possible to add a bathroom on the second floor in any space? We have some attic space on top of our garage which is close to a bedroom on the second floor. Will it be possible to add a bathroom in that space, so the room will have an attached bathroom? If not the room also has a big walk in closet. Please help! Thanks.

speedball1

Is the garage attached to the house? Yes, It's possible if you have a connection for the drainage.
However, you may not connect into a vent line in the attic without first extending the lavatory vent in the bathroom below up to the attic six inches over the flood rim of the highest fixture, (usually the lavatory) in the attic.
Good luck, Tom