u/Magerle

I'm taking on my first full soundproofing job as a handyman ( i had a guy who was working for me when i booked the job who had a lot of experience but he's since left the business and I've been left with what is quite a big technical build to take on).

This is to stop someone yelling at a computer being heard through a shared wall in an old property with lath/plaster, timber studs, floorboards, cornice and fireplace on the adjascent wall (which I'm planning on building a box to cover hung on magnets and catches..

Only one side of the wall is accesible cavity is 150mm wall is approx 3.2 by 4 meters

Current plan:

• Protect room fully: floor protection, taped walls/doors, extractor running.
• Lift floorboards first to inspect cable/pipe routes and reduce flanking through floor void.
• Cut away existing lath/plaster carefully with multitool, bay by bay.
• Inspect studs, masonry, cables, pipes, fireplace voids and cornice void.
• Insulate under floor with acoustic slab where possible.
• Wall build-up from neighbour side inward:
  • existing masonry/shared wall
  • Tecsound SY100 self-adhesive acoustic membrane
  • existing timber stud zone
  • 75mm Rockwool RW5 acoustic slab
  • approx. 25mm acoustic air gap
  • iKoustic MuteClips + channel / resilient bar system
  • Gyproc SoundBloc plasterboard
  • acoustic sealant to perimeter and joints
  • Tecsound layer / GTEC plank where specified
  • second plasterboard layer
  • all perimeter gaps sealed with acoustic sealant

Materials ordered:

• Tecsound SY100 x10
• Rockwool RW5 x10
• iKoustic MuteClip Standard x20
• iKoustic MuteClip Channel x6
• Standard resilient bar 3m x20
• Siniat GTEC resilient tape x2
• Gyproc SoundBloc x20
• Siniat GTEC Plank x3
• JetRock/Gyproc acoustic sealant 600ml x14
• Gyproc Promix Lite x2
• Thistle ProTape FT50 x1
• acoustic double socket boxes

Sockets:

• two double sockets in the wall
• use acoustic socket boxes
• seal penetrations carefully

Ceiling/cornice:

• not opening ceiling void
• stopping at cornice
• plan to pack behind cornice with mineral wool and seal gaps as best as possible

Fireplace:

• chimney/fireplace is likely a major flanking path
• plan is to build a removable soundproof box/panel around the fireplace
• considering magnetic location/attachment so it can locate cleanly and be removable

I could really use some advice here guys.

Goal:
Complete in around 10 working days with one labourer. Main concern is avoiding first-timer mistakes that destroy performance.

Questions:

1. Am I insane for trying this?
2. Anything obvious that I have missed?
3. Do i need to rethink anything before ordering?
4. Fitting the soundproof sockets anything I should bear in mind?
5. Anything you'd change before I start cutting?
6. Any sequencing advice for doing this cleanly with one labourer?
7. Anyone got a candle they can light for me and say a hastily whispered prayer?