I recently posted we were going to install laminate flooring, but we had high spots in the floor. Was going to use self leveling compound and learned you could not put that on partical board underpayment. Decided to look under house and found sagging floor joist. Our house is 30x40. There is a double 2x8 down the middle with 15' on both sides. I noticed that 10' in on the side we were going to lay the floor there was a double 2x8x15 with floor joist nailed to one side. This shortened the span to about 10'. On the other side of the double joist and down that side of the house the floor joist spans are 15'. There is a brick pillow with one of the floor joist on it, half way of the 15' span, about 10' from the double 2x8. Seems to me there should have been a double 2x8x15 here to. It is this way, all way down this side. Wondering what would be the best way to level the floor joist. There is many joist sagging. I'm a electrician by trade and my carpentry termanology is not real good. Hope this is not confusing.
Unfortunately it is very confusing, at least to me. A good step would be to post a few pictures. Even better would be a scaled diagram showing the framing of the joists and the beam (the beam is the doubled 2x8 you mentioned a couple of times. As for fixing sagging framing, that topic has been discussed many times on this forum, and it would be worth your while to do a search and read some of the threads, there are many recommendations on how to measure the sag, how to fix the sag, and how to prepare the subfloor.