Soundproofing an RSJ (!) (with pics)

[mark482]

Hi all,

I am undertaking a (lengthy!) programme of soundproofing in my 1930's semi. On taking down the ceiling in my living room I found that the wall above the bay window is supported by an RSJ which goes right through from my house to the neighbour's:

It seems (from an informal "how much can I hear their TV" test) this is a major path of sound between the houses so I want to block it up.

I was thinking expanding foam and jam some rockwool or something into the inside of the RSJ? Does this sound ok, or any suggestions?

 

[Deluks]

Rockwool yes, expanding foam, no way, too rigid.
Double plasterboarding the ceiling will help too. You might want a covering of rockwool on that wall as well as a stud/plasterboard wall, the rsj/padstone will transmit sound into the wall.

 

[mark482]

Thanks, was thinking about double boarding the ceiling. The plan is to put soundcoat on the party wall then build an independent stud wall with rockwool and double board - got some good advice about that on here a while ago, just getting round to actually doing it!

 

[JohnD]

you can get a dense, rubbery plastic mat that deadens sound - sorry I can't remember where from - that you can wrap round structural members that carry sound through the building. The weight of it deadens some noise and you can use absorbent fibreglass batts in the cavity as well.

 

[Deluks]

epdm rubber in sheet form is sometimes used in HVAC applications. Something like this?

Or what's used under car bonnets for sound deadening? This?

 

[noseall]

i concur with what's already said.

sound absorbtion and sound deadening are achieved by using a combination of space filling fluffy lightweight materials coupled with dense heavy materials.

two layers of plasterboard coupled with fibreglass quilt sounds ideal to me.

some smaller gaps between joists and brickwork or small cracks could be foam filled? or just point them with mortar.

 

[mark482]

Thanks for all the suggestions hadn't thought of wrapping it in a sheet, will look into that. As you can just about see on the right of the 2nd picture I have filled around all the joists with mortar (+ brick for larger gaps). The ones in the bay are loose and waiting for me to level them...