Insulating awkward spaces concerned interstitial condensation or thermal bridge

[buildlondon363]

Hi,
I am doing some renovation's to a Victorian single skin building which is into flats.
One floor I was going to insulate the floor with rockwool sound insulation as it can be very noisy between flats and help retain heat in basement flat. It will be lived in so heat produced. The interstitial floor I wish to insulate the way the joists run I’m not sure if I should insulate to the edge of this as it will be then touching the external brick. Also above the is is some decorative timber to n which is hollow and not insulated. I thought about taking this off to insulate too but then would I need a vapour barrier ? Some of the wood seems to have had damp in past but I believe that was due to tenants drying clothes and not opening windows etc. there was just the floor boards before no insulation. Now I’m wish to insulate and then put boards back and laminate.
Ontop of this there seemed to be some woodworm so I am going to treat with an appropriate treatment. Do I just leave these end voids but then does this create thermal bridge ?

Thanks in advance

 

[Wayners]

With kingspan it will insulate and be a vapour barrier as it's covered in foil.
CharlieDIY on YouTube covered this when he applied to single skin wall.
Id pack that floor void full of Rock wool.
I have insulated walls sticking kingspan on with foam then the plastic fixings through.
People should be using a dehumidifier when drying clothes inside. Unfortunately with renters you can't do much about them creating moisture and not keeping it under control.
Ignorance and modern living

 

[buildlondon363]

That’s for your response Wayners. Yeah probably just do rockwool, no vapour barrier as both flats are heated. What plastic fixings did you use for kingspan? Did they then go into the brick? Thanks

 

[Wayners]

That’s for your response Wayners. Yeah probably just do rockwool, no vapour barrier as both flats are heated. What plastic fixings did you use for kingspan? Did they then go into the brick? Thanks

TIMCO PIF70 TMCO Plastic Insulation Fixing-M8 x 70-Zinc-Bag of 100, White, Set of 100 Pieces https://amzn.eu/d/inRnnmT

That sort of thing.
I think it was Charlie DIY on YouTube covered it

 

[^woody^]

Floors don't have vapour barriers.

Don't think too much, just put the quilt into any gaps.

You also need to consider sealing the floor in terms of compartmentation and hot smoke and flame, not just noise.