I have a basement with nothing roughed in and want to install just a shower. The main drain pipe is within 6 feet of the where the shower will drain. They are both against the same wall where the main drain line runs out of the house. My plan is to cut through the floor and run the shower drain to the outside of the house, then connect it to the main drain outside the house.

2 questions,

1st, is there any concern with hooking into the line after it has left the house?

2nd, do I need to install another vent, or will the vent that sits just upstream (about 6 ft.) be sufficient?

Thanks

2 questions,

1st, is there any concern with hooking into the line after it has left the house?

2nd, do I need to install another vent, or will the vent that sits just upstream (about 6 ft.) be sufficient?

(1) no
(2) Let's see, 6' over to the sewer from the shower trap and 6 more feet from the connection to the upstream vent. That makes your developed length 12 feet. With a 2" drain the accepted length is 5'. With a 1 1/2" drain it's 3 1/2'. Unless you can move the shower closer to the main and the vent you'll have to roll a drainage tee or a wye up on a 45 degree angle just after the trap or very close to it and run a vent out of that.
Be advised that since the shower will be the lowest point in the system any backups will come out of the shower drain. Good luck, Tom