Dead load of attic floor when floored 20 lbs.
Attic storage load limit.
Scrap of plywood over the chords and set about 40 lbs.
To simplify you can place 20 pounds of dead load per square foot on your subfloor as long it s supported mid span.
Live load on second floor local requirements.
Of stuff on it.
If the attic has the potential to become a regular living space talk with a contractor about adding a fixed stairway.
Access to attic storage.
Your allowed weight and span for a 2 x8 x12 2btr hem fir based on the info you have provided is 20 psf of dead load and 30 psf of live load with minimum bearing length of 0 68.
Of floor area dead load of partitions 20 lbs.
Dead load of first floor ceiling not plastered 10 lbs.
So if your ceiling is unfinished you have some excess carrying capacity up there.
However if the attic is intended for storage the attic live load or some portion should also be considered for the design of other elements in the load path.
Storage space dead load of partitions 20 lbs.
That means you could lay a 2 x 4 ft.
Design live loads will vary based on a number of factors but at a minimum 10 psf live load for attics without storage 20 psf live load with limited storage and 30 psf for habitable attics.
Of floor area dead load on second floor 20 lbs.
Dead load of first floor ceiling plastered 20 lbs.
Make sure items are spaced so that the weight is evenly distributed over the chords.