does anyone have an outdoor dog run? i was thinking of attatching one to the back of house so they jump through dog flap into a run but i was wondering if they would pee/poo in it? it would be on concrete and they obv usually pee on grass? anyone else used one and found they wont poo/pee in it?

I've not had a problem mine 'go' on grass or in the run

Same here. My dog run backs onto what was once grass, nice & shady in the summer but can be shut off when it becomes a quagmire in the winter.
I would say make sure you have proper drainage for the concrete run, makes life a lot easier for cleaning.

I have a run with a concrete floor and the dogs have no problem 'going' in it. If you have boys, you could maybe put up a temporary 'pee-post' till they get the idea, but I doubt they will need much encouragement :)

No problems here either. When I let them out the first thing they do is have a good sniff about and promptly pee. Cleanings simple enough, I just use a hose pipe, trigene and a stiff yard brush.