Adding joist support after removing hearth bed

[sys044]

I removed concrete hearth beds in both upstairs bedrooms as there was signs of cracking on the ceilings below in one of the rooms. When I removed them I found a substantial amount of concrete sitting on nails and the ceiling below.

My question is how to add joist support to this opening to support the subfloor I will add.

My original plan was to add a couple of spanning joists parallel to the chimney breast using joist hangsrd and then spanning them. However I can’t see how the circled joists are supported by the chimney breast. What is the correct approach here?

 

[ree]

OP,
Is this on the first floor? Whatever, its hard to clearly see the details.
Remove all the nailings, & all debris or the floor might squeak.
Pic #3 should work - you dont need hangers, simply angle the 31/2" or 3" screws - skew them in.

FWIW: No flue vent can be seen in the chimney breast - redundant flues need smoke testing, sweeping, & venting bottom and top.

 

[sys044]

This is on the 1st floor, slightly concerned as I can’t see where the chimney breast supports the joists circled in green.

No vents on these chimney breasts, will investigate further!