we had a long concrete apron,about 15ft wide,in which we set up 10 smidely huts off to one side,partially on the concrete and partially off, about half the hut.locked them up when they farrowed and let them out for the first three days, twice a day,then after that we left the doors open all the time.we turned them over every 21 days. did it for 15 years.it was the overflow for our farrowing house and worked pretty good.