Second you must vent directly to the outside whether you vent through the attic or wall to meet today 39 s code requirements.
Dry venting 1 bathroom first floor 2 bathrooms second floor.
This setup requires an in line centrifugal fan mounted in the attic drawing air simultaneously from both bathrooms see photo.
Venting 1 2 bath on 1st floor i don t know what code you guys go by or where you can put an aav below the flood level rim of any sink but it sure won t fly with nspc in nj injustice anywhere is a threat to justice everywhere mlk.
It would appear to be easier to install a wall or floor fan and direct exhaust down and then out through basement wall just above ground.
First this is very do able.
Once the new plumbing is in place you can add fixtures and furniture to complete the room.
Add value and convenience to any home by installing a new bathroom on an upper floor.
If the new bathroom is on the second floor the bathroom s main drain will have to travel through the wall on the first floor and down to the basement or crawlspace.
How to vent a 1st floor bath.
In single story homes the duct.
But while you can t have two fans with one vent you can make one fan and one vent serve two bathrooms.
My bathroom is on the first floor with a finished bedroom directly above and an unfinished basement directly below.
You d often blow air from one bathroom into the other and local building inspectors wouldn t approve it.
The vent that services a fixture must have a diameter at least half as large as the drain pipe but the minimum pipe diameter allowable is 1 1 4 inches.
Adding a bathroom to the second floor of your house.
I have read that moist air naturally rises so it is easier to vent up.
Bathroom fans also called exhaust fans prevent moisture damage and mold by forcing air through a duct to the outside of a building.
Irc section m1501 1 outdoor discharge.
The air removed by every mechanical exhaust system shall be discharged to the outdoors.