Mixing MDF and plasterboard for walls

[OpIvy]

I've spent a lot of time researching before I start to build my small 2.4mx 2.0m vocal room in my garage.
I'm sticking to single stud framing, insulated with 2 layers of wall boards on each side mainly due to cost, space and no need for a huge amount of isolation. The room is mainly for vocals and some DI guitar (no amps) and I don't have much external noise to worry about.

One thing I can't find good information on is how effective it is to mix plasterboard and MDF.
I was going to have an internal layer of 18mm MDF covered with 16mm fire-rated plasterboard (sorry but no inches!) on both sides. Where I live there's not much difference in price between the two types of board.

Given the level of isolation I need, is this feasible or am I better to use the 16mm plasterboard then a layer of say 10mm (which is cheaper) and no MDF at all? I would've thought 18mm MDF is much denser and and would provide better isolation....
Also, would it be reasonable to have two plasterboard layers on the exterior but a layer of MDF and layer of plasterboard on the inside? I'm not sure how mixing materials would affect anything....
Cheers

EDit: should also mention that moisture should not be a problem where I'm building

[John Steel]

Hello again Opivy,
Have you seen Greg's transmission loss calculator? It will tell you what kind of transmission loss you can reasonably expect by using various materials. If you know what level of isolation you need, work with the calculator until you find the ideal combination of materials that will achieve it. Best wishes, John.
https://www.johnlsayers.com/phpBB2/view ... =1&t=21770

[Paulus87]

Hi,

Regarding mixing different materials for wall assemblies, there's no direct benefit from using different materials - once the various materials are attached together they essentially become one mass. Just use the cheapest materials with the biggest surface density. If you need to use MDF and there's not much difference in price then you can use it, it has more surface density than drywall.

Paul

[OpIvy]

Hi,

Regarding mixing different materials for wall assemblies, there's no direct benefit from using different materials - once the various materials are attached together they essentially become one mass. Just use the cheapest materials with the biggest surface density. If you need to use MDF and there's not much difference in price then you can use it, it has more surface density than drywall.

Paul

Thanks for the replies.
I've since recalculated the costs and it does seem a layer of MDF will be quite a bit more expensive than plasterboard.
I think I'll stick with a layer of 13mm and layer of 16mm plasterboard.
MDF was a bit more attractive because it allows better fixing to walls for shelves, etc but it's probably not worth the extra cost and hassle of putting them up.

[anodivirta]

Hi,

Regarding mixing different materials for wall assemblies, there's no direct benefit from using different materials - once the various materials are attached together they essentially become one mass. Just use the cheapest materials with the biggest surface density. If you need to use MDF and there's not much difference in price then you can use it, it has more surface density than drywall.

Paul

I remember reading somewhere about sound coincidence frequency, was there some benefit of mixing different materials from this point of view?

[Paulus87]

Hi,

Regarding mixing different materials for wall assemblies, there's no direct benefit from using different materials - once the various materials are attached together they essentially become one mass. Just use the cheapest materials with the biggest surface density. If you need to use MDF and there's not much difference in price then you can use it, it has more surface density than drywall.

Paul

I remember reading somewhere about sound coincidence frequency, was there some benefit of mixing different materials from this point of view?

This is mainly when using two individual masses either side of an air gap, for example using two different thicknesses of laminated glass either side of a window. But if the densities are already high and the cavity resonance is already low enough then the use of different thicknesses/densities is no longer required and in actual fact the benefits of using as much density as possible for both partitions/panes is advisable since it improves overall transmission loss.

Paul

[anodivirta]

Hi,

Regarding mixing different materials for wall assemblies, there's no direct benefit from using different materials - once the various materials are attached together they essentially become one mass. Just use the cheapest materials with the biggest surface density. If you need to use MDF and there's not much difference in price then you can use it, it has more surface density than drywall.

Paul

I remember reading somewhere about sound coincidence frequency, was there some benefit of mixing different materials from this point of view?

This is mainly when using two individual masses either side of an air gap, for example using two different thicknesses of laminated glass either side of a window. But if the densities and cavity resonance is already low enough then the use of different thicknesses/densities is no longer required and in actual fact the benefits of using as much density as possible for both partitions/panes is advisable since it improves overall transmission loss.

Paul

yeah, that was it! thanks:)