Fixing joists around chimney

[messimagician]

In my loft I have the chimney stack from first floor ceiling to first floor. The neighbors have completely removed all their stack.

I would like to remove what's left in ours. I'm also in the process of wanting to put larger joists 9x2 in the loft that will span 4m. These will be sat on 45mm packers. We're having to use huge packers to match the hight of the UB. 152x89 to keep floor flush rather than having the beam poking up through the floor.

The green line will be where the new 9x2 joist will be going. This will leave a 250mm spacing between wall and joist.

Before that I will need to splice the existing 3x2 ceiling joists to cover 0.5m gap of the chimney stack. What would be the best method ?

My next question is how do I cover the 250mm gap between the new joist and wall. Use a couple of masonry hangers to bring out timbers to the new joists to break up the 4m span then use smaller 4x2 joists directly over the old 3x2?

 

[cdbe]

Put another 9x2 against the wall (or spread out the others a bit more if within tolerance). Fix the ceiling joist to it.

 

[messimagician]

I was hoping to keep the 9x2 separate from the existing ceiling joists. If I placed the 9x2 by the side of the 3x2 that would leave 100mm from the wall and be difficult time get a fixing in I think

 

[cdbe]

The correct way is to put a new joist in. If you don't want to do that (and realistically there won't be much loading on the floor that close to the wall so it should be ok) then just bodge it any way you see fit. To splice the ceiling joist just use a length of 3x2, fix with woodscrews and at least 600mm overlap.
As you're retaining the existing ceiling joists I presume that either there aren't any binders or hangars, or you've found a way to retain them? I had to remove all mine so I fixed the old ceiling joists to the new floor joists.