Securing backboxes - Plastered and proving challenging

boxrick · 2026-02-09T10:11:36Z

Hello folks! I am currently trying to acoustically all my back boxes which with metal ones is quite straightforwards. I put caulking around the edges, pop the cable through and then add my acoustic putty to the back as shown below.

The issue is with 'fast fix' boxes which have been liberally used all over. Which sadly until I was plastered didn't realise had been used so far through my build. They are littered everywhere which is very unfortunate since we literally had open studs and could have used metal ones everywhere.

Anyway, right now this is presenting me a real issue since I cannot install pattresses and install the standard metal ones, I cannot add wood to the sides to screw from the front into since I am plastered.

Does anyone have any suggestions? Simply put I need to get the backboxes in and fixed solid which will then allow me to 'finish' around the edges, backs and side with my acoustic seal and putty and it not move again.

I am thinking some of these may do the trick which seem to have a spring which lightly clamps them in until the faceplate is installed? Or is there any available with ratcheting type lugs? Or maybe foaming the boxes in?

https://www.builderdepot.co.uk/bg-2-gang-47mm-fire-rated-dry-lining-box-hgs07-fr