Overlapping lower arms as support

[jokar]

I am currently making a hole in the joist between the upper floor and the attic floor to accommodate a wider staircase.

Unfortunately, this affects two bottom chords of the trusses.

The hole is represented by the blue line.
The affected part of each bottom chord is marked in pink.

Image 1: upper floor
Image 2: attic floor. The red lines show my proposal for staggered bottom chords.
Image 3: attic floor. Red lines symbolize what I perceive as a classic reinforcement. I want to avoid this.

Svenskt Trä writes the following: https://www.traguiden.se/konstrukti...asar/omlottlagda-takasar/omlottlagda-takasar/

Does anyone have experience or wisdom to share regarding my proposal with staggered joists instead of “classic reinforcement”?

 

[Mats-S]

Suggestion 2, what is the difference in width between your transitions and the existing underarms, i.e. the "air" between the beams that need to be transitioned?

 

[jokar]

Proposal 2, how big is the sideways difference between your support beam and the existing joists, i.e., the "gap" between the beams to be supported?

Thank you, Mats! The hole is 1935 x 1350 (blue lines) CC distance on the joists is 910 mm Outer edge of existing beam to chimney: 140 mm (bottom in the picture) Outer edge of existing beam to bedrooms: 200 mm (top in the picture) The length of the overlap can essentially be as long as needed. But for the sake of example - let's say 1000 mm. It is desirable to splice a beam (1000 mm) onto the existing beam and then join with another beam outside (1935+1000+1000 mm). This way, about 90 mm would be freed in both directions, meaning the staircase width would not be limited to 910 mm but 1090 mm. But if this destroys the construction with a 45 mm beam between the existing and the new one, it is still desirable to be able to lay a new beam overlapping as per image 2. Then it would be 45 mm freed in both directions, meaning the staircase width would not be limited to 910 mm but 1000 mm. Since the hole is 1350 mm wide and a joist on each side only needs to be 45 mm adjacent to the chimney and wall respectively, one could achieve a hole of 1270 mm using the same method. However, it would require two 45 mm beams on top of each other before building the new beam. That might be a bit too wide overlap, even if the overlap can be very long?

 

[jokar]

I made a simple sketch.
Realize that the new reglarna could be 70mm wide instead of 45mm. But that's a question for later.

 

[jokar]

Does anyone know a recommendation on overlap/wraparound?
Where you can see sizing, etc.