Sealing gaps in acoustic plasterboard

[KnightWhoSaysNi]

I'm having my loft conversion done. I asked the builders to use SoundBloc plasterboard on the party walls to improve the sound insulation. It's now fully plasterboarded (with a single layer of plasterboard), but there are gaps between the adjacent boards, from 2mm to 10mm for the most part.

I'm thinking to fill the gaps with an acoustic sealant (AC50 specifically). The builders, however, say the plaster won't stick to it and will start coming off in a few months, and are trying to dissuade me. What should I do? I've already ordered 6 bottles of said acoustic sealant.

 

[stevethespreader]

I've had a look at the spec sheet and it says can be used for sealing plasterboard or as an adhesive to bond plasterboard to plasterboard and can be used In drylining applications and can also been applied to fresh plaster using pva, I used to skim for a boarding firm and quite often mastic was used at edges mainly fire retardant mastic and the skim stuck to it ok , this kind of mastic is made so it can take a finish it says it can be used in drylining applications so it can be taped over and finish applied also don't forget between boards you will have scrim tape if it was me I would use it but its down to you at the end of the day

 

[stevethespreader]

I've had a look at the spec sheet and it says can be used for sealing plasterboard or as an adhesive to bond plasterboard to plasterboard and can be used In drylining applications and can also been applied to fresh plaster using pva, I used to SKim for a boarding firm and quite often mastic was used at edges mainly fire retardant mastic and the SKim stuck to it ok , this kind of mastic is made so it can take a finish it says it can be used in dryling applications so it can be taped over and finish applied also don't forget between boards you will have scrim tape if it was me I would use it but its down to you at the end of the day

May have been similar to stuff like this which is also sound proof all much the same really can all be used on board
http://shop.vitcas.com/vitcas-intum...c-1201-p.asp?gclid=CIre_reK5MkCFcLnGwod40QCgw

 

[KnightWhoSaysNi]

Cheers. I'll go ahead then. Yes the specs say it's meant for sealing gaps between boards, but the builders had given me second thoughts.

And yes, they are using scrim tape.