I am going to be cutting into a 4" stack pipe to add a 2" T that feeds a new shower/sink. About a foot above where that T will go is where the toilet line meets the stack. Do I need to support the vertical stack with a riser clamp or can I just support the horizontal line from the toilet with a long 2x4?

I am going to be cutting into a 4" stack pipe to add a 2" T that feeds a new shower/sink. About a foot above where that T will go is where the toilet line meets the stack. Do I need to support the vertical stack with a riser clamp or can I just support the horizontal line from the toilet with a long 2x4?

This would be putting weight on the branch of the fitting causing undue strain on the joint. Better be safe then have the cast iron come crashing down. Use a raiser clamp on trhe vertical section of the stack. Good luck, Tom