how much room in the run?

my chooks have been allowed to free range in the garden since i got them 5 weeks ago, however my bf is starting to complain rather a lot about them pooing on the garden  (even though i poo pick everyday!) and has set about making a run, the frame of which is complete, just waiting for the wire tocome.

It is 9 feet long by 3 feet wide and about 4 foot high, so i can walk in albeit crouching a little, would this be big enough for my 3 chooks??

i have told him that they are going to have to be let out once a day or a couple of hours to range as it is just not fair!

If it's too small an area they will soon trash the ground. As Joyfull says the larger the better. Just make additional frames to enlarge the area. Better if you can move them around your plot as well to keep them on fresh grass.