Impact of fixing OSB on sound transmission

Ansur

New member
I'm converting my third floor / attic into a studio. In the process of doing so, I'm trying as best as I can to provide some sound isolation.
We're talking about a 100+ year old house here - so it's not going to be an easy task. With that in mind, I'm not looking to block the sound entirely, just the best I can without breaking the bank.

Right now I'm working on the floor - the old one has been ripped out, and I've straightened the wooden beams. What I have in mind is to fill the space between with isolation (+- 20cm), and actually place three layers of new floor:
- acoustix panterre (a Belgian product meant for sound isolation)
- OSB boards
- wooden floor as finish

My initial idea was to place the first two layers floating, and glue the wooden floor to the OSB.
It seems though, that the OSB should be fixed to the beams with screws. I recall reading this would be bad for sound isolation, but good structurally.

Sound isolation is rather confusing at times - is adding a few screws immediately having a big impact on the global sound transmission, or is the effect limited?
 
Well, first off, when you say that you've straightened the "wood beams", do you mean the floor joists? And what do you mean "straighten" them? Are you talking about levelling the floor joists? And to do this, did you 'sister' additional joists along side the exisiting in an attempt to level the floor?

IMO, if it's not the first layer that you install directly on the floor joists, just from a structural point of view ONE of the three layers should be fastened to the joists. You don't want the floor bouncing and making noise because the 1st layer (OSB?) is moving up & down at points where there may be a bit of a sag in the joist system. And as far as the hardwood finish-flooring. Yes, there are adhesives sold for this purpose, but personally (I've installed 1000sf+ in my house) I wouldn't rely on adhesive-only. The adhseive helps - but I nailed mine WITH adhesive too, directly to 3/4" sub-floor grade(no voids) T&G plywood, which was also was both nailed and glued (to the 10" floor joists), in an effort to have a "never-squeak" floor and guess what... there are still spots where there's a bit of creaking.

As far as the sound isolation part - others here can better address that.
 
I don't know about hardwood flooring, but with laminate, you do it as 'floating' - a layer of foam over the subfloor, with the laminate tongue-and-grooved together over it, no nails/screws or glue. If the hardwood is tongue-and-grooved, not nailing it through would be no issue, but if it is just flat-edged boards, it's got to be attached to the subfloor.
 
Fill the gaps between the beams with insulation.
Attach OSB to the beams with screws. Use plenty of screws -- for that matter, use a double thickness of OSB.
All good structure is not good isolation, but all good isolation begins with good structure.
NOW, you got a good, solid, useful floor that you can THEN start your isolation from. Whether that's iso-pucks or foam board or whatever. The iso part is pretty cookbook from there. Start with good solid structure every time. It's been said: you don't want it moving.

Ponder5
 
Many thanks for the replies.

bLUiVORY, I did exactly what you described: additional planks have been attached on the side of the existing wooden beams.

So if I get it right, I should now just place the isolation layer on the beams, then the OSB. I can screw the OSB at this point onto the beams.
 
Many thanks for the replies.

bLUiVORY, I did exactly what you described: additional planks have been attached on the side of the existing wooden beams.

So if I get it right, I should now just place the isolation layer on the beams, then the OSB. I can screw the OSB at this point onto the beams.

Ansur - Sounds like you're off to a good start, and sounds like a good plan. Being a 100 year old structure, they may be 'beams', after all. What are the dimensions of the floor 'beams'? That may be some pretty hard wood, there. If so, I hope you've got a good, heavy-duty power drill with a side handle for screwing all those screws. Oh! Think about running any additional wiring through those floor joists before you button things back up. Unless you're always going to have access from the ceiling below. Just a thought...

A 100 year old house - that's pretty cool. In what part of the world do you reside?
 
Good point from Blu, my house is 110 years old. When I had walls/ceilings exposed I ran cable (tv) and telephone (landline) cables into every room. Any exposed water pipes - wrap the supply pipes with foam tubes (not just the hot water) to muffle sound, and wrap fiberglass insulation around any heating and drain pipes.
 
Yep. This is the time to think of anything at all you may possibly need in the future. Hell... I might even run speaker wire, couple of balanced lines, cable for direct boxes, headphone extensions... whatever. And maybe one of those 'Talkin' Tubes' like the ol' U-boats had, so you can say, "Dive! Dive!" Anything that's a possibility. Run 'em down & under and back up into a far wall. If you never use it... meh, no big loss. But if you develop a need and it isn't in place - big PITA.
 
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A 100 year old house - that's pretty cool. In what part of the world do you reside?
I'm living in Antwerp (Belgium), in a typical city "mansion" (not sure how to translate it) from the turn of the century. To get an idea, look here.
Looks nice, but isolation (both acoustic and thermal) is terrible!

You make a very good point regarding running wires - I've already foreseen some electrical wires and I should indeed run some audio cables as well.
The beams are 17x6 cm (6.7x2.36 inches). I've added 17.5x3 cm (6.9x1.2 inches) planks to it, to level them out.

I must say, construction in itself is something I can get into - and lot's of information and help to be found. Acoustic isolation is an entirely different game. Still I read / hear people saying I should definitely NOT use screws to fix the OSB boards, but it does sound like a safe approach to add them for structural reasons.
 
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