My dog wont stop pooping in my kitchen?

we have a 2year old german sheperd and we have had him for a gd few months now, but, we cant stop him pooping in the kitchen, we have cleaned it with, a cleaner hoover, bleach, disinfectent, carpet freshner. we do tell him of for it, but we wont it to stop coz he always seems to have the runs which make it worse for us to clean. he had previous owners, but we take him for walks and we have a open carport that he goes outside in? we love him to bits but it is becomiong a pain.....what can i do?