Drain outside back of house blocked when shower runs drain fills and smells and what can only be described as poo!! Come up (is this normal when blocked) and any tips to unblock please help!

drain outside back of house blocked when shower runs drain fills
Are you referring to a outside floor drain or a cleanout?
Are you on a city sewer or a septic tank? Back to you, Tom

Are you referring to a outside floor drain or a cleanout?
Are you on a city sewer or a septic tank? Back to you, Tom

Its an outside drain not a septic tank my neighbours are fine is it best just to reach in see if it's a block!!

This "outside drain" is tied into your sewer line and the sewer line's blocked downstream from it.
Are you on a city sewer or a septic tank? Let me know and We'll get into the repair. Cheers, Tom

Just to answer your question: Yes, it is normal.

As Tom explained: All drain are connected together at one point. If this drain gets clogged up - sewer will back up exiting out of lowest open drain. In your case, that happens to be your outside drain...

( Just FYI: In my area, it is not allowed to tie site drains to the sewer pipe. We have to run site drains to the curb. )

Snake the main drain and you will be fine...