wrangling acoustic insulation with 1st fix

[mvincentd]

My 1st floor metal web joists are boarded but open below, currently only with mvhr ducting running through.  Should I add acoustic insulation before 1st fix....it would surely be far easier than after.  Most images/illustrations i've seen show the acoustic sitting on the ceiling board with an air gap above to the floorboards.  I'd have thought it would be easier to maintain comprehensive acoustic insulation if its set high where it doesn't interfere with spotlights etc.

 

All internal partition walls are stud work for pb'd and skim.  After 1st fix electric and plumbing is in I expect to pb one side then add acoustic insulation.  How do I account for electrical wires and the risk of insulation leading to them being de-rated.....or have I been reading too much and understanding too little??

[nod]

39 minutes ago, mvincentd said:

My 1st floor metal web joists are boarded but open below, currently only with mvhr ducting running through.  Should I add acoustic insulation before 1st fix....it would surely be far easier than after.  Most images/illustrations i've seen show the acoustic sitting on the ceiling board with an air gap above to the floorboards.  I'd have thought it would be easier to maintain comprehensive acoustic insulation if its set high where it doesn't interfere with spotlights etc.

 

All internal partition walls are stud work for pb'd and skim.  After 1st fix electric and plumbing is in I expect to pb one side then add acoustic insulation.  How do I account for electrical wires and the risk of insulation leading to them being de-rated.....or have I been reading too much and understanding too little??

 

This is how we normally do it prior to boarding 

[ProDave]

I slotted "planks" (pallet wood) through the joists to support the accoustic insulation.  The thinking being if I ever needed to fish a new cable through I would stand more chance with a small gap between the PB and the insulation

 

[mvincentd]

Thanks for the useful pictures....think I was looking for problems where there aren't any.  I saw someone else just run string where you used pallet board Dave.

[CC45]

I've done the same as @ProDave.  Good use for all those little bits of wood lying around.