As an interim update, I'm still working on the fabric of the space insofar as there is an huge amount of insulation ongoing which in conjunction with the aforementioned back injury (improving though it is) is proving time consuming.
However, things are progressing, in no small part due to my wife getting stuck in with gusto and doing many eaves-related things, which is brilliant as she is a 'proper grafter', getting loads done and significantly smaller than I am which facilitates under-roof matters considerably. On my part, the floor has been relaid (glued this time) over the rockwool and isolated joists...
... on her part, the walls are pretty much insulated ...
... also on her part, the floor under the eaves has been completely cleared of the old cruddy insulation ...
... and she's rapidly installing rockwool, with a view to finishing tomorrow.
Back to my part; the rear-most stud wall on the party wall has been backed with breathable membrane and insulation has started on that also although I'm down to my last 2 bales and the eaves floor is taking priority.
Next up, and hopefully completed by the end of Sunday, is the the studwork over the stairs and the 'battening out' of the roof joists, which need thickening to accomodate 125mm of rockwool with a 50mm gap behind it.
This involves some logistics as there are stacks of 2-by-4 and battening on the scaffolding outside which need to be cut to length up high on the scaffold and shipped into the space via the window apertures so it should be a fun day, especially if it's raining
I've also measured up the ceiling. Inner (ridge to the inside of the outer wall) and outer (ridge to the breathable soffit) dimensions as well as the skeiling and will be ordering the 50+75mm rockwool for the ceiling, the additional 2x2 battening and 100mm rockwool for the skeiling during the day tomorrow. Also the 100mm rockwool for the stair-walls below, the short wall in the eaves, the walls of the storage area at the stair-end of the room, the double thickness party wall, and the enclosure over the stairs.
There is also some framing to be done in the access stairway. An order of acoustic and normal plasterboard will follow along with the resilience bars for mounting the former.
One thing I would mention for anyone doing the same or similar is that there is a slight vibration of nearby objects if I jump up and down in the center of the room. I weigh 17+ stones (107Kg/238lb) but I'd rather it wasn't there and if I'd known beforehand I'd have got the builders to sandwich some additional bars of steel between some of the double floor-joists. I can live with it.
Will - spoke to the sparky yesterday and he too recommended poking holes in the plasterboard for the lighting wires, so consider that a given (I was going to anyway in light of your comment). On a related note I'll also be creating some story-poles/strings for identifying locations of timber studs going forward.
The next order of rockwool and other supplies will be quite a big one, but at least there is a floor to put it on now.
Soldiering on and for any who are wondering, much studio-specific stuff will follow. This is all the foundational stuff, mainly concerned with soundproofing, which precedes talk of acoustic treatment/dispersion, ceiling clouds, bass traps and so forth