Sandwiching PDF & Gypsum Board for Ceiling

bolehnggak · Post by **bolehnggak** » Thu Oct 30, 2003 2:13 pm

Hi,

For my studio, I'm going to put 2-ply gypsum board for soundproofing the ceiling, with rockwools inside the ceiling frame, no channels.
But I'm offered by a friend to buy his unused MDFs, so I'm going to ask you all. How good MDF is compared to gypsum board for ceilings?
I'm thinking of sandwiching a ply of MDF with a ply of gypsum board, which I thought maybe better, since the sound would travel across two different medium. Is it true?
Any comments? Or maybe other suggestions other than MDF and gypsum? Plywood are far more expensive here, so don't suggest that, unless it's really good for soundproofing.

Ari

bolehnggak · Post by **bolehnggak** » Thu Oct 30, 2003 2:19 pm

Oops, sorry about the title, it's not PDF, obviously.

It's MDF.

Ari

knightfly · Post by **knightfly** » Fri Oct 31, 2003 1:51 am

Hi, Ari, welcome back - I've learned from our last discussions on prices NOT to assume anything, so I'll put it this way - MDF is heavy, so would be a good material for sound proofing. It also has a different speed of sound travel than gypsum, so you're right about the change. If you can get MDF at a good price, there's no reason NOT to use it - for the same thickness, it should be similar to gypsum in isolation, plus the difference in characteristics should make for a good sandwich.

Here in the US, MDF is over twice the price of gypsum so I tend not to recommend it - however, this is strictly a cost issue, not a performance one... Steve

bolehnggak · Post by **bolehnggak** » Sun Nov 02, 2003 3:37 pm

How about two layers of MDFs, with different thickness, example 12mm and 15mm sandwiched together? Is it better than a 12mm MDF with 15mm gyspum, or 15mm MDF with 12mm gypsum? Just curious, cause I got a lot of MDFs here from used partitions that had been torn down.

Ari

knightfly · Post by **knightfly** » Sun Nov 02, 2003 7:48 pm

Different thicknesses of MDF should be fine, Ari - As I mentioned when I answered your post over on HR, there are several different "flavors" of MDF, so it's hard to say what yours is like. Generally, though, if you use different thicknesses and stagger all joints, it should work at least as good as gypsum. Keep in mind though, that fastening will be different than gypsum - you'll need to drill and countersink all screw holes, and you'll still need to fill any cracks before applying the next layer... Steve