Supporting joists for stairs

[Wibbles]

Hi all,
I am at the early stages of thinking about moving a staircase. Putting aside the fact that I know I need building regs approval and a structural engineer to validate any plan, I'm looking for some general advice on how an opening is made into a floor.

I have two pics. Pic A shows the house as it is now: about a 3.5m span with joists running across structural walls shown in green. It's an old house so I expect they are quite low spec joists but have yet to confirm.

I am looking at putting a staircase in as per Pic B. The staircase is shown in orange. I think therefore I need to add some structure as shown in red to support the cut joists.

How is this normally done?

Thanks.

Pic attached:

Untitled

• Wibbles
• 2 Jan 2012
• 1

 

[RedHerring2]

I think you'll need to double that joist running alongside the stairs and then install a double header across the stairs.
You might need a triple alongside the stairs.

I assume you'll have a landing at the top. You've just not drawn it in.

 

[Wibbles]

Yes, thinking of the last three stairs being a quarter turn onto the landing area.

More for interest than anything else, I'm trying to get my head around the structural calculation - I get the idea of what you can do with a single span and height x width and separation between joists, just not quite sure I understand how you calculate the load if you cut through the joists and hang them off another as per the stairwell diagram.

Maybe I should have studied to be a structural engineer