12.5 and 9.5 wallboard

[Rod Gervais]

Originally Posted by antony

Hi.

I've proofed the live room with rock wool and 12.5 wallboard. I have extended and want to add to the soundproofing. So im going to put resilent bar and another layer of drywall over the existing drywall. I've read that two layers of wall board are better but at different thickness. Does it matter which thickness sits on the stud or is it same difference.

Thanks

Antony.

Antony,

there is no advantage to using differing thicknesses of drywall - use the thickest you can afford..... this is about mass - 16mm is better than 12mm and is much better than 9mm

There is (however) a huge disadvantage to using resilient channel in between layers of drywall - very highly NOT RECOMMENDED..... if you need to decouple in order for this to work for you - first remove the drywall so you can attach the resilient system directly to the studs.

Rod

[antony]

Cheers for reply.

Would you suggest putting a rubber matting against the stud then resilient bar then drywall.

Antony.

[Rod Gervais]

nope - the matting is next to useless............

[antony]

Cool saved me some there. Last one what about rubber devider between joist and wall?

Thanks

[Rod Gervais]

does not work well for the purpose of decoupling,

[antony]

Great cheers, so basically the usual brick,stud,rock wool,resilient bar then drywall works best on the basis more mass better results.

Thanks

[Rod Gervais]

and if you slide that stud wall away from the brick it is even better than the resilient channel without the added cost.......

[antony]

I don't think I have the option to do that as I am only having to do one wall and the ceiling which is a 20ft eave ceiling. Guess I could fix it to the side walls but would that defeat the object?

[Dange]

Originally Posted by Rod Gervais

there is no advantage to using differing thicknesses of drywall - use the thickest you can afford..... this is about mass - 16mm is better than 12mm and is much better than 9mm

Rod, I did hear from a reliable source that 2 layers are better than one of equivalent thickness in terms of sound insulation. So 2 x 10mm will be better than 1 x 20mm. By how much I don't know. The difference is caused by the fact the two sheets flex and rub against each other, that friction gives extra losses.

[kasmira]

Originally Posted by Dange

Rod, I did hear from a reliable source that 2 layers are better than one of equivalent thickness in terms of sound insulation. So 2 x 10mm will be better than 1 x 20mm. By how much I don't know. The difference is caused by the fact the two sheets flex and rub against each other, that friction gives extra losses.

This makes sense on an impact level, but I really don't see it making a large difference in actual SPL measured. Maybe, though, curious to hear his input on this as well.

[Sebg]

20mm drywall would have a coincidence frequency in a much less favourable frequency band compared to 10mm. That is one good reason - the other as you say is some friction damping. No studio guy ever complained about enough low freq sound insulation and not enough mids and highs - usually the other way around. So the damping is a secondary and less useful benefit.

[Rod Gervais]

Sebg is (of course) correct - which is why it is recommended that you do not laminate sheets (i.e. glue them together) when constructing isolating wall assemblies - that essentially creates a single sheet....

The best possible bang for the buck is multiple layers of 5/8" (16mm) drywall.

Rod

[AndreBenoit]

Originally Posted by Rod Gervais

and if you slide that stud wall away from the brick it is even better than the resilient channel without the added cost.......

This is very useful advice for space restricted builds; I have been planning to convert my garage for some time but worry about the loss of space & as such was considering a resilient channel system. Does this mean I will gain as good a result by simply moving the studs away from the brickwork, even if it's only by as much space as the clip & channel would have taken up?