Here are a few pictures of our pen - it is a 10 X 10 chainlink dog kennel that sits on concrete paver stones. They have two plastic dog houses, that I drilled holes in the bottom and sides for ventilation and "liquid" drainage. Since these pictures were taken, I covered half the floor with outdoor carpet runners to protect their feet from the concrete. In the winter, I filled the houses with about 6 inches of hay and covered the floor with about 6 inches of oak leaves. During warm weather, I just take a hose and spray out the pen with a water hose after I let them out in the mornings. They free-range during the day.