Loft Floor Ideas

[webbm]

I plan to put in a loft extension and I want to get as much headroom up there as possible. Hence, I don't want the new joists to be any deeper than necessary. There are two single skin wall between back and front rooms( see picture). The bedroom ceilings joist sit on them. Is there any reason why I should not use this to support the end of the new joists?
The Orange and yellow lines show what i would like to to do.

I'd like to have some idea before approaching Building Control.

show what i would like to to do.

I'd like to have some idea before approaching Building Control.

 

[freddiemercurystwin]

Do not think that Building Control will offer design advice, that's not within their remit. Are those walls loadbearing? Often some existing roof structure needs to be removed which usually demands a steel beam or two be installed. You probably need to employ a designer. Certainly a structural engineer if the structure is being altered.

 

[webbm]

I think both the wall are load bearing wall as they hold up stairs case and and ceiling joist sit on them