Breaking into loft joist question

[liamruairi]

Doing my own loft conversion and about to break through the ceiling to install new stairs. New floor joists are all flying above current ceiling joists and don't touch them. Question is, when I cut the existing ceiling joists to chop out the hole, how do I secure them? Do I just screw trimmer battens into the cut ends around where I chop them? Or is there a 'proper' way to secure the opening? Have attached a basic diagram of what I mean. Black lines are existing ceiling joists. Blue lines are stairs, red lines are where I will cut, and green lines are proposed 'trimmer' joists / battens.
Thanks in advance.

 

[liamruairi]

Or like this; where trimmer is attached to wall via a joist hanger and attached to the end of each cut joist via another joist hanger

 

[Ian H]

I can’t see your PDF but don’t screw into the end of the old joists. Donit at an angle.

 

[liamruairi]

Sorry have attached as jpeg.

 

[Ian H]

On my I doubled up all around (purple) and rebuilt strong stud walls below (Orange). Building control were happy with that although I did balls it up because the stairs turned at the bottom so I had to shift them a bit to give enough head height.

 

[liamruairi]

Ok cheers for that. Cant build walls underneath as there's another staircase underneath but theres no weight going on this floor; the new floor flies above it. Will double up and fix temporarily with hangers until bc come out and see what they say. Thanks

 

[bobasd]

the key to what you propose is the new joists.
surely this existin an proposed carcassing was all shown in the drawings you submitted for Bldg. Regs?

 

[liamruairi]

the key to what you propose is the new joists.
surely this existin an proposed carcassing was all shown in the drawings you submitted for Bldg. Regs?

Yes you’re quite right but the new joists don’t touch the existing joists they fly above them, just wondering how best to secure the existing ceiling joists once I cut them for the new stairwell. The new joists above will be all double trimmed around stairwell

 

[bobasd]

i now they dont touch but all that stairwell detail should have been worked out an approved in advance.

talkin of "flyin above them" means what?

if this is a non BC approved job an your askin such questions then you could be at risk of buildin unsafe stairs/floor?if this is the case i'd at least get a joiner on site for the carcassin?

 

[geraldthehamster]

g

 

[liamruairi]

i now they dont touch but all that stairwell detail should have been worked out an approved in advance.

talkin of "flyin above them" means what?

if this is a non BC approved job an your askin such questions then you could be at risk of buildin unsafe stairs/floor?if this is the case i'd at least get a joiner on site for the carcassin?

Sorry I'm not being very clear am i?! It is a BC approved job but the plans I have from my structural engineer are pretty crap I'll be honest, and the building control officer I had has left the company last week and the new one won't come out until the stairs are in! I at least need to secure them temporarily to get stairs in. My plans do say all joists around stairwells too be double trimmed with doubled up joists etc. I know this; and don't have a probem with that. What I'm trying to ask (not very eloquently!) is what is an acceptable method of fixing the existing ceiling joist ends (which will be cut)? Can I bolt a multi truss hanger into the wall and hang a doubled up trimmer from this to the first 'full uncut' ceiling joist? Then I can hang the cut joist ends onto this using jiffy hangers. As in the pictures above.

The new floor joists are sitting above all this attached to a wall plate at either end of house and sitting on a steel beam running across the middle of house.

 

[liamruairi]

...Or failing that could I use these extra long jiffy hangers to attach the trimmer joist to the existing wall plate that the new floor joists are hanging off? https://www.toolstation.com/shop/p15421