And 100' is about the limit with routers you get off the consumer shelf. If the outbuilding is on the same power circuit I'd try powerline networking instead as over 100' is hit, miss and just drops out without notice.
I've got an AT&T "hotspot" as my home wifi. Would like to extend it to and outbuilding (about 150') from my house. Feasible? If so, what would be recommended?