I want to add storage space above our 2-car garage by building a floor in
the garage's attic and adding some drop-down stairs, so it's easy to get to
the garage's attic.

Problem is the attic has 2x4 engineered trusses spaced every 2 feet apart,
so I would have to add joists to support the weight of the floor, the weight
of anyone walking up there, as well as the weight of the boxes and things
that I'll be storing up there. I'm planning on using 3/4 or 1 inch plywood
for the flooring in the garage attic.

The garage is 22 feet wide (the trusses go this way, so the trusses span 22
feet) and 20 feet deep. Would I need some kind of beam going down the middle
to support the additional joists, so they wouldn't have to span the full 22
feet?

What's the easiest way to add and support joists and a floor in a 2-car
garage attic? The 2x4 trusses are, of course, resting on the walls of the
garage, and there doesn't really appear to be a way to put any taller boards
for joists (i.e., 2x8s or 2x10s) between the roof and the top of the garage
walls since the only thing that will fit there now is the 2x4 ends of the
trusses. It would be nice if I could just add 2x4s to the bottom of the
trusses to make those thicker and stronger to support a floor, since they
would fit perfectly between the tops of the walls and the roof, but since
the trusses are spaced every 24 inches, rather than every 16 inches, as
normal joists would be spaced, I'm guessing that won't work.

Has anyone done a similar project in the attic of a 2-car garage, and if so,
how did you do it? Any advice or suggestions would be appreciated!!

--
DK