Attic finish, floor

I have an unfinished attic that I would like to finish for a nursery/bedroom.  The problem is that the floor joists are true 2x6, which span around 20ft.  I am waiting to hear back from engineers, but in the mean time I was thinking about adding 2x10 or 2x12 16" o.c. in between the existing joists.  I know this would raise my floor about 3-5 inches, but I have enough head room.  Would this be a reasonable option?  I'm trying to do as much of this by myself to cut costs.

Matt C

Matt,

Your on  the right track about adding additional floor joists along side the existing 2x6 rafters.  That is how it is usually done.  For residential living areas, some 2 x 10's can span up to 16'5" and some 2 x 12's can span up to 19'1".  To achieve a 20' span, you will probably have to go to an "I" joist, TGI Pro 230, 11 7/8".   Verify this with the manufacturer.  Good luck and good remodeling.

Jake