Assuming the construction was done properly, would 3/4" OSB (oriented strand board, it's like a particle board but better) a better soundproofing material than 5/8" drywall?
This OSB has an R-factor of 0.90, which is really good. 1/2" drywall of course is abysmal at 0.45, but actually 5/8 drywall isn't much better with an R-factor of 0.5625.
Compare this to common brick. Brick has an R-factor of 0.80, so the OSB has even a brick wall beat.
1" plywood actually has an R-factor of 1.25, just a side note.
Soundproofing has several elements:
- mass (weight, density)
- airtight
- absorption (e.g. foam [good] vs thin steel [bad])
- damping (e.g. green glue)
- resonance (e.g. foam [good] vs metal [bad])
Mass is non-negotiable. If you put two sheets of 1/16" plastic together with green glue and make it airtight, it still isn't going to do much. And because plastic has little absorption, the sound may well pass right through. So that's an example of a poor design.
OSB seems to kill it with mass. Not only is it nearly the same price as drywall, but it has nearly double the R-factor of 5/8 drywall. In fact, it's similar to having two sheets of 5/8 drywall (without green glue).
That's not the only benefit of OSB. If I wanted to put it on a hinge or screw something in, OSB is a lot greater material since it can hold a screw, and not crumble under its own weight. It's possible with drywall but you also need to build a full frame for it which not only increases the cost and resonance (both bad) but is a ton more work.
The downside of OSB is finishing it, but for some applications it doesn't matter. The best way is to seal it with resin, or sand and paint before install. If you don't need to finish it, there isn't much downside to OSB as far as I can see.
Also, cutting to shape is easier and less messy. There is some sawdust but drywall has drywall dust which is way more messy for install.
The only thing I don't know about is resonance of OSB. However, being strands of wood held together with glue, I'm guessing it should be at least comparable to drywall if not better – but this is just a guess so don't take my word for it.
You could even put two layers of OSB with green glue, and anectodal evidence says it is about the same benefit – except that the 3/4 OSB will have double the mass of the 5/8 drywall, so possibly far greater sound reduction.
So, can 3/4 OSB be a better bet for soundproofing than 5/8 drywall, for the same installation?
Best Answer
3/4” OSB board is better than 5/8” gypsum board.
Sound control is measured in STC ratings (sound transmission coefficient).
Here’s a website that tests various materials: https://www.ecopacificinsulators.com/uploads/4/7/1/6/4716609/sound_transmission_stc_rating.pdf
Gypsum board is not as good as OSB board. 1/2” OSB board equals 5/8” gypsum board.
As you can see, 3/4” OSB board is not listed, but OSB board increases by +1 for each 1/8” thickness. Therefore, you could surmise that 3/4” OSB board would be +6, and 5/8” gypsum board is +4 and fire rated gypsum board is only +5.