Advice on modifying floor joists

[MarkandCath]

We are renovating a house and need to move the head of the stairs back to allow for a new staircase with a left turn at the top. I originally thought the header ran just the width of the staircase but after lifting the floor I found it runs the whole way to the outside wall.

In the picture. I can install 2 new joists further back where I need them- red in the picture. I can then cut the header along the blue line and remove the old header to the staircase. The problem I have is I need to leave the header to the left of the cut in place BUT it will no longer be supported by the brick wall.

What I am thinking is another joist (marked in green) and then coach bolts to lock all 5 joists together. I can't believe it will move but I am not a structural engineer. Any advice would be much appreciated. Cheers.

 

[blup]

Worth speaking to an SE, the spec of the bolts plate and tooth washers is important. Quite apart from the loadings

 

[Jurassicspark]

Doesn't look like a DIY job to me.

 

[cdbe]

Looks ok to me. The only potential issue I can see is twisting of the truncated headers but unlikely with the incoming joists. Have you considered a l shaped bracket bolted to the wall below?

 

[Notch7]

I think what you are proposing is a potential solution, but as Blup says, a S/E specifying what you do is best.

You may need some steel plates

It’s made more difficult by the pipework….