Run-in sheds have better ventilation and less accumulation of dust mold and spores than what accumulate in a normal barn. Individual horses have the opportunity to regulate where they want to be, and that's good for the horse's health and psychological well-being. Run-in sheds allow horses to act more like real horses. They're very horse friendly. In the summer, it protects the horse by providing shade and also protects the horse from flies by being in the shade, as flies don't go into the shade as much.
Many sheds contain a feedbox and water trough, and some are extended to house hay, grain, and tack.
But for run-in sheds to provide maximum safety and protection, it's critical they be constructed and sited properly. Siting The Shed Probably the first consideration for your run-in shed is to identify the best place for it to be built. It should be located in an area that offers good drainage so horses aren't standing in muck and dirty water. Either have the shed on a slope so the liquid drains away, or consider grading the site by putting in gravel and top soil over it. Of equal importance, situate the shed so the open face is opposite the side where prevailing winds come from, in order to provide shelter against cold northern winds or hot summer blasts.