Normally, you can only build one facility with the Space Yard abilities on a planet. However, it is possible to upgrade from a different facility in the same family to a facility that is a Space Yard. Thus, the Space Yard Expansions were born. They allow you to specialize a planet as a construction world with extremely high production rates, at the cost of resource production, research, intel, etc. There are 3 Space Yard type facilities in Adamant Mod (essentially):
These are identical in purpose to the Space Yard facilities in stock SE4. You just build one, and it lets you build ships, and increases the rate of construction on the planet.
Space Yard Expansion Project
This facility by itself does absolutely nothing. It has no abilities. But, this is how you start building a second Space Yard on a planet. First, you have to hit the "show obselete" button so that obselete facilities are visible. Then, you build a Space Yard Expansion Project (there are 3 different kinds, one for each resource type), and then upgrade it to the appropriate Space Yard Expansion facility. The Space Yard Expansion Project and the Space Yard Expansion are in the same family, so this upgrade is possible.
Space Yard Expansion
Instead of allowing full Space Yards to be built with the expansion method, these were added with greatly reduced rates. They are still very useful, though. It is possible to build a Space Yard Expansion before you have a Space Yard on a planet. This is a bad idea though, as you will have greatly reduced construction rates on the planet, and will not be able to build a normal Space Yard unless you scrap the Space Yard Expansion.
Fill Queues: You can use the Fill Queue function to avoid having to show obselete facilities every time you wish to add a Space Yard Expansion Project to the build queue. Simply make a build queue consisting of one Space Yard Expansion Project, then click on the Fill Queue button. Then, click on Add Type, and add an appropriate name. Do this for each Space Yard Expansion Project type. In the future, you can simply click on Fill Queue and select that type to add a Space Yard Expansion Project to the build queue, without having to show obselete facilities and navigate through the lengthy lists. (Aiken)