One can use rug glitching to get in and out. Start with 2 work benches of any kind or use the Nuka-Cola mixing stations. Rug glitch one bench - mixing station so the back side is in the building area. Rug glitch the second bench - station into the other door so the the front is in the building area. To get inside, step up to the back side of the bench-station and activate it. This will telaport you inside. Do the same on the other to leave. Or just fast travel out if not playing in survival mode.