How to soundproof the gap between plasterboard and floor

[jacoscar]

I’ve built a 50mm metal stud wall with acoustic fiberglass in the void and boarded with 15mm acoustic plasterboard

I have left around 18mm gap at the bottom and now need to fill it

The subfloor is latex self levelling compound over plywood, I’ve started filling the gap with the leftover of easifill from the mix I made to fill screw gaps and butt joints, but I wonder if I could use acoustic expanding foam and have a similar acoustic barrier

I care slightly more about not having a weak spot (in terms of acoustics) rather than rising damp due to possible spillages

 

[endecotp]

You can get acoustic silicone sealant, but 18mm is a bit too big perhaps.

Search Toolstation for “acoustic sealant” and you’ll get both silicone and expanding foam types.

 

[fenny666]

Sorry mate but it begs the question...Why did you leave an 18mm gap when you went through all the effort of using rockwool and 15mm soundblock/shield? Nevermind, I'm sure there was good reason What you need is mastic. Google Knauf mastic to give you an idea. It will improve your 'acoustic barrier'. This should be used around the perimeter prior to boarding for the best performance. But for you it is still the best option if considering acoustics.

 

[jacoscar]

Sorry mate but it begs the question...Why did you leave an 18mm gap when you went through all the effort of using rockwool and 15mm soundblock/shield? Nevermind, I'm sure there was good reason What you need is mastic. Google Knauf mastic to give you an idea. It will improve your 'acoustic barrier'. This should be used around the perimeter prior to boarding for the best performance. But for you it is still the best option if considering acoustics.

Because rooms and ceilings are never square, so if I cut boards the right size, I wouldn’t be able to put them in place (it touched the ceiling)