Intermediate floor buildup incl. floor levelling

[alfaTom]

Evening all,

 

First post outside of my hello thread from yesterday and I think it'll be a good'un. If you've not seen the hello thread with a little background on the house/situation (subsidence!) check it out here:

 

Onto the question:
How would you level a floor that has a drop towards the external wall?
I have seen a variety of methods and I am not sure which I prefer so thought it best to ask those with experience. The room that we are looking at first has a slope towards the front elevation, and the joists run perpendicular to this. The current joists look to be 7x2" timbers and are in good condition, albeit it is notched here & there for pipework.

 

The flooring is as follows:
------ 22mm T+G floorboards

==== 7x2" timbers
______ Plasterboard ceiling
No thermal or acoustic insulation is present currently.

 

I am torn between sistering the joists and counter-battening to add a service cavity, or taking them out completely and replacing with fabricated I-beams or posi-joists (perhaps overkill, but would make service routing such as rewire & MVHR easier). The span is just shy of 4m and is from one external wall to another, with the joists sitting on the inner leaf in pockets.

 

Current ceiling height is about 2.4m for both ground & first floor so there is some wiggle room.

No work will be completed until the remedial subsidence work is done, so I avoid levelling the floor to have it 'heave' after the subsidence treatment is completed.

Thoughts? Questions?