Plasterboard question from middle earth!!

[Johnrg]

Guys,

I am trying to save a few bucks and the most expensive thing in my budget is plasterboard.

I am building a new floating room inside an existing structure that already has fairly good, well sealed 13mm plasterboard-insulation-weatherboard walls.

I was going to use one 13mm board and one 10mm board glued and screwed for my new wall (23mm) ($37 combined price) but I can get a supply of 15mm board at $25 per sheet. This $12 adds up over the sheets i need.

Do you think I can get away with one 15mm sheet as long as everything is well sealed and caulked.? Will this extra 8mm make that much difference anyway?

This is going to be a small drum/gtar room with this new wall built on a floated floor with a new ceiling on top of the walls. My closest neighbours are about 20feet away.

Thanks for your thoughts

J from New Zealand

 

[Rod Gervais]

I am building a new floating room inside an existing structure that already has fairly good, well sealed 13mm plasterboard-insulation-weatherboard walls.

John,

Are you saying that the walls you look at already have plasterboard installed on them - and you are going to add new framing with a couple of layers of additional plasterboard?

So to describe your wall assembly it would be - existing exterior siding, xisting exterior sheathing - existing studs with insulation - existing drywall - new air space - new studs with insulation - new plasterboard?

If I am describing this correctly - then you are going to have a triple leaf wall assembly - which is going to give you lower isolation than you would get with the same materials in the right location.

The inner layer of existing plasterboard has to go away.

I was going to use one 13mm board and one 10mm board glued and screwed for my new wall (23mm) ($37 combined price) but I can get a supply of 15mm board at $25 per sheet. This $12 adds up over the sheets i need.

Do you think I can get away with one 15mm sheet as long as everything is well sealed and caulked.? Will this extra 8mm make that much difference anyway?

1st off - I would not reccomend that you glue the sheets together - you get better performance with the units acting individually - and not as one sheet.

Yes the extra mass makes quite a difference, but what you could do would be this, place one layer - set up your drums and have a friend play them - while you go outside and listen, if you get what you want and need - then no problems - if not - add another layer and test again. Just make sure you caulk all the outside edges on each layer as you go, and tape the field to seal any air passages.

This is going to be a small drum/gtar room with this new wall built on a floated floor with a new ceiling on top of the walls. My closest neighbours are about 20feet away.

20 feet is pretty close, my best guess would be that you are going to need more mass than the original 10 / 13mm you are talking about.

You might get away with 2 layers of the 15mm, but could possibly need even more than that.

Also - would you please explain exactly how you are creating your floating floor so we can make sure there aren't going to be any problems there?

Rod

 

[Johnrg]

Hi Rod,

thanks for the reply.

I don't consider the outside leaf as a leaf as it's not well sealed at all, so if I take this out of the equation my new total wall is Mass air Mass.

Heres a drawing of my wall plans, including ceiling and floor. I am using the inside out SAE wall because I am really limited on space as you can see from my floor plan!!

Understand about glueing the plasterboard - I may have to see if I can stretch the budget to two 13mm boards just to be save.

Thanks

JG

 

[Rod Gervais]

I don't consider the outside leaf as a leaf as it's not well sealed at all, so if I take this out of the equation my new total wall is Mass air Mass.

John,

I understand your thoughts on this - but you're mistaken.

Even if the leaf is not well sealed - it's still acting as a leaf - and the middle leaf will still diminish your isolation.

You would be much better off removing the inner layer and sealing the outer layer - perhaps adding some additional mass in the process.

If you cut the inner layer of drywall with a recriprocal saw carefully at the framing edge - you could reinstall it within the stud bay and caulk the edge to seal.......... same mass - only addition cost for the caulk - some additional labor - but a heck of a gain from the perspective of isolation.

Something to think about.

BTW - i see you're a left handed drummer.......... so am I.

Good luck,

Rod

 

[Johnrg]

Hi Rod,

thanks for the reply.

I suppose here in lies the problem.

I cannot touch the existing walls at all apart from caulk any airgaps and sealing the two windows in this room - this is part of the lease.

So my questions are:

(a)What can I do to provide the required isolation bearing in mind I can only afford one new wall with two sheets of 13mm board, i only have a maximum of 200mm in which to work and I can't touch the original wall which is already two leaf system - theres a tricky one for you!!

(b) I understand the principals of a three leaf system but if I have no choice but to build the walls these way what kind of % reduction in TL and/or STC will I have .

Thanks for your help - I am hoping there must be some solution or at least a compromise that is weighted in my direction.

JG