I am converting a basement storage closet to a bathroom, & am laying out the Toilet, shower, & lavatory drains. What I need to know is how big & where I should vent the drains. This seems to be a big deal here code wise. The Lavatory will be about 10 or 12 feet from the Original Sewer stack, This 1 ½ inch line will Tee into the 4 inch line coming from the toilet, then that 4 inch line will pick up the shower about 4 feet from the Stack. The Toilet will be about 10 feet away from the stack. This is going to be in the basement, so I will be breaking up the floor to do this. I will saddle on to the Sewer below the floor, & will run the vents to the attic, where I will join to old stack to reduce holes in the roof. Any help with this would be appreciated.
Thanks

I think you answered your own question when you said it was a big deal there code wise. I would go to your local building inspection office and garner the information from them. I could tell you what it is in my area, but, it may not fly in your area. Most inspectors are more than happy to give out the information.
A 10 foot distance to the stack pipe is not code in my area, so, another vent is needed.
I do not agree with your saddle concept since they can cause problems down the road. I always tap into the sewer lines with a plastic pipe connected by one or two Fernco type fittings if necessary.