Unlock an additional spec.
If you choose one spec for your Tech Lab, you can build another Tech Lab later and choose a different spec. — sharpo, 06/16/16
If you have a Tech Lab but have not built a Tech 2 building, you do not choose a spec for your Tech Lab. Later when you build your Tech 2 building, you will choose the spec for the Tech 2 building and for the Tech Lab. — sharpo, 06/16/16