As it turns out, the reason different builders can make a moonbase build, yet have it fit another moonbase is due to a standard created by the LEGO Space Community (you didn’t know there was a space community, did you?) back in 2002 to connect corridors between different builds.
2 Rules to Build a Moonbase
If you want to try your hand at a moonbase build, there are two very simple rules you’ll need to follow:
1. You’ll need to get your hands on a 48 x 48 stud grey baseplate (also called an x-large baseplate.) All moonbase builds are started on this type and color baseplate.
2. Each build should connect at one (or more) of four predetermined points to create a Corridor Connection to a neighboring module. This is where the instructions for making moonbase corridor connectors come into play.
Instructions for Making Moonbase Corridor Connector
If you’d like to try your hand at making a moonbase, you can use these instructions to create your moonbase corridor connectors. You’ll also need to keep the following things in mind:
- Corridor floor plate is 10 bricks off of the baseplate.
- End of corridor is flush with baseplate edge.
- Corridor is 6 studs wide.
- Corridor is centered along baseplate edge.
- Airlock ring is 8 studs wide.
- Doorway is 4 studs wide by 5 bricks tall.
- 2 1×2 Technic bricks (the ones with the hole in the middle) are centered half way up the doorway.
- Use any supports you like, but the base of the supports should be at least 4 studs from the baseplate edge.
If you’re a more visual person, you can see what that looks like in the following diagram from the Brickfair Alabama Moonbase wiki:

Look up “lego space 2012” for the complete and actual moonbase specs. These are limited.
Thanks Michael! You don’t have a link for me, do you? Having trouble finding those full specs.
Sorry to necro this, but this might be what the original commenter was referring to:
https://www.flickr.com/photos/bumcrush/sets/72157624888198989/with/5015218913/#