Two-car garage construction
I suppose there must be a way you could splice dimensional lumber and make a longer span, but... why?
Have a look at wood I-joists. Boise Cascade (BCI), LP Building Products (SolidStart) and Weyerhaeuser (TJI) are three options widely available in the US. (photo below from lpcorp.com)

As a single point of reference, a BCI span table shows spans up to or exceeding 24 ft with joists 11-7/8, 14, or 16 inches deep with spacings of 12, 16, 19.2, or 24 inches on center. You'll have to consult the table yourself to see the effects of joist family, spacing, allowed deflection, and loading.