Hoop barn is a housing design and you could put a gestating crate or farrowing stall inside if you want.
Usually it is used in fatteners. Some say it is better for you will have good ventilation and it is roomy for the fattener. Draw back would be the cost to build.
In some cases they use a hoop barn to house sow, they can move more freely because they are not confined in the gestating crate. But heat detection is much more difficult in this situation.
