Normally, I would have the door go to floor level of the family room. But in your case it will have to go the the top of the stair nose proud. Yes, the gap would depend on your hardware, mine have a gap of approx 1/2".

You could install blocking on the wall to build the door past the nosing, then run the door to the floor.

Barn doors come longer then standard interior door openings to compensate for the upper hardware. If a normal door is 80" a barn door of 84" would be used. By raising, lowering the mounting you can have it end up anywhere from 1/2 from the floor to the middle of the step up. You can also cut the door to gain another inch or two of clearance if needed.

If you arent putting blocking in the wall you will have to put a 1x on top of your finished wall to attach to. This of course pulls the door out from the wall apex 3/4" so you would have about 1 1/2-1 3/4 out from the wall. If you have blocking you can go as close as 3/4" which should clear moldings.

Look into a soft close soft open track it makes a big difference and the cost is nominal. Even buy the soft close separate it is less then $100.

Thanks for your comments.

You are going to hate doing this job, I am a carpenter of 16 years. i hate hanging barn doors, as much as I hate pocket doors.

Your door needs to go to the elevation of the floor nosing. The door has a guide, that supports and centers the bottom of the door. that guide needs to be screws down to a structurally sound thing. it needs to be installed perfectly. good luck.

I have 2 barn doors on my master bedroom closet. We installed them ourselves. However, the wall was being built at the same time so we were able to install additional support before the drywall went on. We used two large reclaimed doors. You can use any size you wish and we have a friend that built his own rustic looking door. You don't have to use specific sized "barn doors". As to the noise, that will depend on your hardware. We used steel on steel and they do make some noise but it is not that loud. I imagine that you wouldn't be moving the door much in your setting anyway. Would love to see the finished area.

I feel that aesthetically the barn door needs to go to the floor and to do this moulding will need to be added to reach past the nosing. Concept shown in photo.

Here is a puzzle for you Joseph ;D

There needs to be a 3 foot landing before a door at the bottom of the stairs...

Fred:

A landing the length of the door and track would solve the door height problem wouldn't it?

I appreciate all the feedback. I had no idea how difficult this was going to be. There is a Murphy bed in the family room for guests and so we do need the door for privacy.

Joseph, can you please explain your comment? thanks!

OR .... you could just tile it, since some people think that you don't have to follow any of the other building codes that aren't in the TCNA handbook if you use tile. ;)